B. A. R. C.-994

I

u

GOVERNMENT OF INDIATOT^ 33T? 31W 1*1

ATOMIC ENERGY COMMISSION

ANNUAL REPORT OF THEMETALLURGY DIVISION

Period Ending December 1977

Edited by

K. Elayapcrumal, Ch. Sridhar Rao, P. Mukhopadhyay and S. V. K. Rao

Metallurgy Division

BHABHA ATOMIC RESEARCH CENTREin, vnra

BOMBAY, INDIA1979

B. A. ft. C.-994

GOVERNMENT OF INDIAATOMIC ENERGY COMMISSION

i

CP

ANNUAL REPORTOF THE

METALLURGY DIVISIONPeriod Ending December 1977

Edited by

K. Elayaperumal, Ch. Srldhar Rao,P. Mukhopadhyay and S. V.K.Rao

Metallurgy Division

BHABHA ATOMIC RESEARCH CENTREBOMBAY, INDIA

19T9

INIS SnViimt C«t«*orr t telf ttt

Pforlptortt

BXTRACf IVE METALLURGY

PHYSICAL METALLURGY

RESEARCH PHDGHAJO

ZIRCONIUU ALLOYS

BERYLLIUM ALLOYS

CERAMICS

URANIUM DI0XI1E

ZIRCONIUM OXIDES

COfiROSICN

NIOBIUM

VANADIUM

NICKEL

IITANIUM

00NTBRI3

1 . Suamary frogresa Report for 1975-77 •• •• ** ( i )

Annual Report t 1977 • (ir)

8. Extractive Metallurgy . • •• •• 1

3» Ihysioal Metallurgy •• •« *» 25

4* Oorroalon and Electrometallurgy •• •• •• 95

5» Cerantes •• •• •» 73

6* List of Publication! . . •• •• 91

7* Metallurgy Colloquium Series 100

8* Seotional Staff Charts •« •• •• 102

BHABHA ATOMIC HBSBARCH OESTHSHBTALKJROY DIVISION

1• Summary Progress Report f o r 1975-77

The Metallurgy ELTIsion i s engaged i n a wide v a r i e t y of

programmes dea l ing wi th s p e c i a l mater ia l s development f o r nuclear* spaoe

and electronic applications, and the elucidation of materials behaviour

in engineering systems* The programmes cover extraction metallurgy,

physical A mechanical metallurgy* alloy development, corrosion metallur-

gy, and ceramics, including property evaluation of both metallic and

ceramic materials* The three year period 1975-77 has seen substantial

progress in a l l these fields* The following are some of the highlights

of major achievements i

Process Development & Pilot Plants

1• Work i s in progress to set up a Beryllium Pilot Plant at

Vaghi, with an i n i t i a l annual capacity of 10 tonnes of Cu-2$3e alloy

and 250 Kg of vacuum hot pressed beryllium metal* The project i s In

collaboration with the Departments of Space and Electronics*

2 . Regular production of boron carbide and boral sheet has been

undertaken for meeting the requirements of reactor programmes* Ring-

shaped boro- carbide - aluminium composites have also been successfully

fabricated«

3* In the Titanium Pilot Plant programme, fluidlsed bed ohlorl-

nation of rutile to produce TiCl. at a rate of about 20 Kg/hour, and

fused salt electrolysis of TlCl* in a refractory-lined 1000 amp

electrolytic c e l l have been successfully demonstrated*

4* Process flowsheets nave been developed for ( i ) recovering

nickel and molybdenum values from the sulphide concentrates of TOIL,

( l i ) preparing vanadium-base materials from the by-products of the

aluminium industry, ( i l l ) fabricating Nb-Ti superconductors, and

(lv) re-processing of elrconium scrap*

(il)

5* A method has been developed for graphite coating of zlrcaloy

fuel tubes to minimise pellet-clad Interaction in power reactor fuels*

6. A technique for hard wear resistant chromium plating has bean

dereloped to meet some of the requirements of R-5. The wear resistance

Is required in the metallic seals of the lattice tubes* It is/proposed

to plate the entire metallic seals of H-5* j

7* In a programme on the development of plate type fueJ( elements

made of high density, thin, sintered platelets of UO and UO^-ZrOg,, the

powder preparation and fabricational parameters have been optimised.

3* In the field of high temperature ceramic materials for the

MHD channels, sintered high density bodies of Al 0, and KgO with

optimum porosity have been successfully developed based on admixtures

of fused and active oxides which would withstand the severe, service

conditions in the MHD channels*

New Equipment Facilities

1 • A Scanning Electron Microscope has been installed and is being

extensively used for studies on failure analysis of components from

various units of BAB and for characterisation of fine met^l powders*. 4

2» A new Transmission Electron Microscope has been installed andi s being used for studying phase transformations and other structuralaspects in zirconium-base alloys and other nuclear materials*

3* A freeze-drying unit has been designed and commissioned for

the preparation of ultra fine particles of metal oompounds for further

conversion to fine metal powders required in the preparation of porous

metal components of controlled porosity*

4* A 5-litre high pressure high temperature autoclave has been

fabricated* Using this autoclave stress corrosion cracking of (i)

sircaloy-2 fuel tube in iodine vapour, and ( i i ) steam generator tub*

materials like inconel, nonel and incoloy In high temperature water hart

been established-

( i l l )

5• In collaboration with Desalination & £f fluent EngineeringDivision, a dynamic corrosion loop has been set-up to study corrosionbehaviour of Desalination Plant materials both In raw sea water andunder various desalination conditions*

Basic Research

In addition to the above listed developmental programmes, theDivision has made very valuable contributions of fundamental signifi-cance in several branches of Materials Science. The Bpedfic fieldsinclude t metallurgical thermochemistry) gas-solid reactions» physical,mechanical and structural properties of cladding and pressure vesselmaterials} mete . physics aspects like diffusion and radiation damage;stress corrosion cracking; passivity, pitting and other electrochemicalcharacteristics of corrosion of metals; electroplating of alloys andcomposites and characterisation of ceramic powders and mechanism ofsintering.

Consultancy and Technical Services

The Division continues to extend Consultancy and TechnicalServloee to several organisations both within and outside DAE, in theform of supply of special materials assistance In carrying out materialsevaluation tests, advice on materials selection and participation infailure analysis Investigations.

(iv)

REPORT t 1977

The major applied research programmes in the MetallurgyDivision have been connerned with (i) development of processes forthe extraction and refining of strategic metals and special materialsof Interest to nuclear engineering, electronics, aero-space, andchemical industries, ( l i ) studies on the physical, mechanical andcorrosion properties of these materials, ( i i i ) development of hightemperature ceramic materials for advanced applications as in the MHDprogramme and (iv) development of special fabrication techniques,involving powder metallurgy and electroforming. Basic researchprogrammes current3y in progress are in the areas of metallurgicalthermochemistry, diffusion, structural metallurgy, radiation damage,corrosion kinetics and sintering. The Division hss also been extendingassistance to several organisations, meeting their specifio materialrequirements, and participating in investigations on materialsperformance and failure analysis.

The settixg up of a Beryllium Pilot Plant (initial AnnualCapacity: 10 tonnes of Cu-2# Be and 250 Kg vacuum hot pressedberyllium metal) - in collaboration with the Department of Space aniDepartment of Electronics - has been approved. There has been goodprogress on the development of graphite-coating of eirealoy tubes,to minimise pellet-clad interaction in power reactor fuel. Ring-shaped boron carbide-aluminium composites have been successfullyfabricated for use aa control rod material. Attractive pyro- andhydro-processing schemes have been evolved to recover nickel andmolybdenum values from the sulphide concentrates in the by-produetrecovery plant of UCIL. Process flowsheets for the recovery ofvanadium in diverse industrially Important usable forms, such as pur*

. . 2 .

( T )

ranadlum, ferxo-vanadlum and vanadium oxycarbide hanre been developed»starting from by-products of the aluminium industry and also fromvanadiferous slag. A plasma furnace facility i s being set up forInvestigating new extractive processes at high temperatures. Moltensalt oleotro-winnlng and electro-refining processes have beencontinued to produce ductile titanium and hafnium, and for thereclamation of sircaloy scrap.

Extensive work has been carried out on phase transformations,structure-property correlations, solid state diffusion and radiationdamage. These studies Include: the martensitic transformation andthe precipitation of metastable and stable lntermetallic phases inthe binary Zr-Al, Zr-Cu, Zr-Cr, Zr-Ta, Sr-Sn, Zr-Nb, Ti-Cr and Ti-Bosystems; rationalisation of the observations in terms of computer-generated free energy varous composition data; the influence of thesecond phase on the strength properties of these alloys; the effectsof a variety of heat treatments on the microstructure and themechanical properties of important structural alloys like xircaloy-2,Zr-2.5Nb, T1-6A1-4T, Ti-8Al-1Mo-1V £nd Ti-6Al-2Sn-4Zr-6Mo; establishmentof a detailed structure-property correlation in the reactor pressurevessel steel HY-13O; diffusion behaviour in the Zr-Pe, Ti-Pe, Th-Pe andZr-Cr systems; the mechanisms of solid solution hardening in a number ofslrconium alloys; microstructural characterisation of some importantsuperconducting alloys and compounds; the effect of neutron irradiationon the mechanical properties of some titanium alloys; ion-irradiationinduced blister formation on several nuclear structural materials; andsetting up of a versatile gas pressure bonding assembly for studyingthe diffusion bonding behaviour of zircaljy-2. Apart from these researchprogrammes, the Division has provided service facilities to externalusers, for transmission and scanning electron microscopy, electron probe•ioro-analysis, and Instron testing.

Studies on the high temperature corrosion of «ircaloy-2

containing aluminium as Impurity have shown that aluminium contents

up to 140 ppm can be tolerated from the view-point of acceptable

corrosion rates. In the high temperature corrosion of carbon steel

in llthiated water at an oxygen level of 0.05 ppm, the corrosion

product release rates have been observed to be extremely low. High

temperature autoclave collapse tes t s for ridging on RAPP fuel pins

have indicated that low yield strength fuel-clad may be aocepted

provided the pellet-clad gap i s less than 0.003 inch. Studies on

stress corrosion cracking (SCO) of zircaloy-2 in iodine nave shown th«t

annealed tubes are susceptible to SCO by iodine during internal

pressurisation. As regards the effects of alloying elements on the

stress corrosion cracking of zirconium, i t has been observed that

iron and copper are not as effective as chromium in imparting

resistance. Nickel, both in the wrought and electrodeposited form, has

been found to be resistant to corrosion in highly alkaline solution,

but this resistance is affected by impurities in the alkaline solution,

particularly HgS. Studies on sea water corrosion in CIRUS Jetty hare

shown that a copper base alloy Cu-9$Sn-4$A1 i s resistant to sea water*

Electroplating of antimony, Ni-lta alloys, Ni-TiOg composites, eleetro-

phoretic deposition of NiO, electrofonning of porous nickel tubes, and

particle-bed electrolysis of dilute copper solutions have been success-

fully carried out in the Electrometallurgy programmes.

In the f ie ld of nuclear ceramics, R & D studies are being

carried out on U02, U02-Zr0. and BeO. A programme on the development

of high-density, thin sintered platelets of DOg and UOg-ZrOg has been

taken up. For the plate-type fuel development, the powder preparation

and fabricational parametors have been successfully optimised* In the

f ie ld of high temperature materials, for the development of high-

temperature oxide ceramics for the MHD channels. R & D studies are

being carried out on A12c>3, jjgO and ZrO2. Sintered high density

bodies of AlgO- and MgO with optimum porosity have been successfully

developed based on admixtures of fused and active oxides which would

withstand the severe service conditions in the MHD channels. Work

hM also been Initiated on rare-earth stabilised slroonls for use

as the hot eleotrodes In these channels* In the field of electrical

oersaios, in addition to the RAD studies on Barium Titanate

capacitor and Ni-2n Perrite bodies, work has been taken up to develop

high density inperrious high alumina components to rery olose dimensional

tolerances - of great Importance to the electronics industry.

( C. T. Sundaran )Head, Metallurgy Division

2 . EETRACTITE METAHUBOT

The major a e t l r i t i e s of the Section were concerned with

s tudies on ( l ) the treatment of ores* concentrates and Industr ia l by-

products for the recovery of s trateg ic metal ral l ies , ( l i ) the extract ion

and ref ining of rare , reactiTe and refractory metals for engineering

appl icat ion , ( i l l ) preparation and fabrication of spec ia l materials for

control-rod, superconducting and aagnet applications* ( l r ) metal lurgical

thermo-chemlstry, ( T ) development of high temperature furnaoes, plasms,

processes , and ( r i ) f lu ld i sed bed reactors* Special emphasis was plaosd

on the development of processes for the extraction of niobium, vanadium,

hafnium, the rare earth metals and n i c k e l , preparation of niobium al lo;n

rare earth a l l o y s , boron carbide and composites) and generation of

process data and equipment des ign . HLgh temperature react ions were

studied to obtain thermodynamlc and k ine t i c data* Regular production of

boral sheets i boron carbide, ferro a l l o y s and other spec ia l a l l oys was

continued•

2«: BORON CARBIDE AND BORAL SHEETS

2 . 1 . 1 Boral Sheets

(CK. Gupta, D.K. Bose, T.K. Mukherjee and K.U. Hair)

Regular production of boron carbide (B.C) by carbothemLc

reduction of BgO, with carbon/ooke In a 50 KW induction furn&ce was

carried out* The product carbide i s being used for preparing the boral

sheets f o r supplying t o the R-5 projec t .

The process standardised for the fabricat ion of boral sheets

involved three main s t e p s , namely ( l ) production of boral block, ( l i )

picture framing of the boral block with alund.nlun and ( i l l ) hot r o l l -

ing to elad-shest.

Boral blocks (200 x 150 x 20 mm) containing 35#(wt)B4O,

dispersed in aluminium matrix were prepared by hot pressing B C (pre-

oxidlsed) and aluminium powder mixture in a graphite die at 700«C and

1-3 kg/cm2 pressure. The blocks wsrs placed Inside a 6 mm thick

aluminium picture frame and jacketted with & 3 am thick alun&aUa plats*

Vent holes (3 am 0) were also provided i n the frame. The blocks thus

encaeed all around with aluminium were heated to 600/610*0, soaked for

half an hour and hot rolled, giving 10$ reduction per pass* On the

average, 9 to 10 paoeca were possible between suoeessive heating cycles*

The sheets were rolled *to a final thickness of 10 m and then cut to

200 x 300 mm sises, as specified*

2*1.2 large Scale Production of B.C

(c.K. Gupta* B.R. Mahendra, P.V.S. PL Halt C. Narayanan

and K.U. Nair)

In cinder to produce boron carbide on a large scale, a direct

electric resistance heating furnace assembly was built and successfully

tested* The furnace consisted of a graphite heating element (25 dia x

5 th x 150 mm long) placed vertically between two water cooled graphite

terminals. The element was assembled in a graphite crucible* which

contained the charge, BuO, »rid coke* An 80 KW single phase transformer

was used to supply the power and heat the element and the oharge to the

reduction temperature of more than 2O0O*C. With 12 KW power input

reduction was continued for 2 hours to obtain dense boron carbide

crystals. Further work is in progress on increasing the batch siM,

and to establish th« operating parameters*

2.2 NIOBIUM AND ITS AXiLOYS

2.2.1 Niobium through Niobium Nitride Route

(S.P. Carg, N. Krishnamoorthy and B* Venkatramani)

An alternative process, to the aliwLnotheralc and carbothendc

reductions for the preparation of niobium was investigated. The process

involved nit riding of NbgOg In presence of carbon under nitrogen atmos-

phere followed by denitriding under vacuum and electron beam melting /

refining of the metal .

m>2o5 + so + N 2 > 2 Nbir + 5 co

2 NbN > 2 Nb + N2

P e l l e t s of oiobiutt oxide and graphite mixture (100 gm) war*

placed In a molybdenum l ined graphite crucible and heated i n an induc-

t i o n furnace at 1500*0 for 2 houra under flowing (500 oc /a ln) ni trogan.

Mtrogen flow v»s then atoppedf the temperature m a raised under dyna-

Btc Tacuun of 10~3 t orr and denltrldlng waa carried out for one hour

at 1950*0* The ae ta l thus obtained waa found to be 99.5JC pure

(130 T i t ) . Further purif icat ion could be achieved by e leetroa beam

•el t -refLnlng and the f i n a l product corresponded to a button hardness

of 70 TJ».

2*2*2 II obi urn by AluulnDtbermlc Seduction

(Q.K* Oupta and C. Rarayane. ,

Over 5 kg of niobium metal was prepared by the alumlno-

thermlo reduction of Hb20c followed by electron beam melting* The U g h

purity metal i s being uaed i n the development programme on Hb-Ti super-

conducting a l loy*

2*2*3 ELobium^tltanium Alloy

(0*K* Oupta. DJC* Boee and C. Harayanan)

In the programme on super-oohductLng Nb-n alloys» a l l o y s

with higher I I oontent were prepared* Various s teps i n the fabrica-

t i o n of oopper-clad Ib-M. wire were standardised. Long length,

OIBO copper-olad wires of 0 . 3 am dia and 25 metres long were prepared*

A t y p i c a l wire containing Nb-25Ti was found t o carry 2 x 105 Aap/cm

upto a f i e l d of 40 kg . In order to inoreass the current oarrying

oapacity (upto 1 x 10 amp/on ) of such wires , a l l o y s with 55-40 wtjfel

were prepared* These a l l o y s were amenable to oold r o l l i n g t o -the

extent of 60£ reduction without intermediate annealing. Short sample

t e s t s on these wires are being carried out at the 1HC, Kalpakkam.

2*3 ZIRCONIUM

2*3*1 Electro-refining of Ziroaloy Scrap

(J .C. Sehra, 1*.L. Tijay and A. Thxxikrishhsa)

In order t o develop m a l ternat ive process for reclamation

of slroaloy scrap, studies on electro-refining technique were continued.

The scrap was obtained from the Nuclear Fuel Complex, for the investiga-

tions on 1 kg scale* Under the optimum operating conditions establish-

ed, dendrltitle deposit of good quality metal was obtained* The overall

•etal yield and the current efficiencies were found to be about 65% and

75-80^ respectively. The electro-refined and arc melted drconlum metal

corresponded to a button hardness of 150 VPN.

Based on these studies, a large scale unit hac been designed

and i s being fabricated at the Central Workshops, BARC.

2*3*2 Al-Zr Master Alloys(T.S. Kriebnan, R.F. Tangri and P.K. Rajagopalan)

Zirconium i s added as a grain-refiner to aluminium, to improvethe meohanioal proper ides* The estimated demand for Al-5#Zr masteralloy for this application i s of the order of 150 tons in the defenceIndustry alone. An enquiry for the supply of 2 tonnes of Al-5J&r alloyhas been received from H/s Indian Aluminium Company. Calcutta.

Two processesf one based on direot alloying and the other on

aluminothencLc reduction of ZrO2 in presence of cryolite for the prepa-

ration of Al-5-15#Zr master alloys were established on the benoh scale .

Based on the results of direot alloying, large scale melts (25-30 kg)

use of the f a c i l i t i e s at Central Workshops have been planned*

2 »3 »3 ferro-ELrconlum

(D.K. Bose and O.K. Hehra)

Verro-sirconlum finds application as an alloying agent and

also as a de-oxldiser in the steel industry* Studies on preparation of

ferro-sLreonlum (50^Zr) by open alumLnotheraic reduction of slrcon war*

carried out on 200 gm (of zircon) scale* With the optimum chart*

composition, namely 200 gm drcon, 210 gm Tf^Oy UO gm Al (15JC SXOSM

over theoretical requirement), 50 gm KClO and 140 gm of freshly burnt

lime, well consolidated massive ferro-sirconlum buttons were obtained*

Zirconium recovery in the process was estimated at

2*3*4 Ceramic Grade Zirconia

(T*S. Krishnan, J.M. JuneJa and P.R. Menon)

Comnercial grade zirconium i s used i n the fabricat ion of

ceramic mater ia l s . Two processes , one Involving lime s inter ing and

another soda ash s inter ing of z irconia were e s tab l i shed ' The

processes involved treat ing zircon at high temperatures (1000-1400"c)

with CaO, NagCO- so as to obtain d i l . acid or a l k a l i so luble s i l i c a t e s ,

which were leached out the product residue was z irconia with about

1jf SLOg* The product y i e l d s were 88-9936. I t i s planned t o sca le up

the operation t o 25 kg batches of z i rcon .

2 . 3 . 5 Graphite Coatings of Zircalpy Tubes

(T.K. Mukherjee, Sudhir Nanda and C Narayanan)

The programme on coating of z irca loy tubes with graphite

was continued using an alcohol based c o l l o i d a l graphite suspension for

the coat ing, followed by drying and baking treatment to obtain 10-15

thick adherent c o a t i n g s . A number of tubes were prepared and supplied

t o d i f ferent groups i n BARC for the evaluation of acceptabi l i ty*

Various t e s t s , both des truct ive and non-destruct ive , - including

thermal cyc l ing , autoclaving and s t r e s s corrosion cracking i n iodine

atmosphere - t o t e s t the qual i ty of the coatings were carried out*

The coat ings have been found to be adherent, s tab le and protect ive*

Further work i s now being organised for t e s t s under reactor environments*

2*4 HAFNIUM

(O.K. Gupta and I .G. Sharma)

t o r the preparation of hafnium metal , a l t ernat ive routes t o

Kroll process were i n v e s t i g a t e d . Experimental s tud ies on calcium

reduction and alundLnothermLc reduction of hafnium oxide, followed by

ref in ing processes l i k e e lectron beam melting and e l ec tro -re f in ing were

carried out*

2*4*1 Refining of Calcium Reduced Metal

Calcium reduced hafnium powder was compacted at 250 kg/cm

pressure t o p e l l e t s . The green p e l l e t s with 4*2 g /co densi ty were kept

l a thorla ooatainers and heated to 900 to 1600ac under a dynamic

vacuum of 5 x 10 torr for a period of one hour, and the influence of

sintering treatscot on pallet density and purification of the aetal

was studied* A maximum sintered density of orer « # of theoretloal

was aohieved at 1100*C, and effective removal of metallic impurities

like iron, calcium, magnesium was observed* There was however no

marked change in the interstit ial impurity content in the pellets even

after treatment at 1600*0*

The pellets sintered at 1100*C were melted in the electron

beam furnace at 2 to 3 KW power level . The melting periods were

varied to study the effeot on the impurity content of the product. At

2.5 KW power level and 120 minutes molt-duration. metal buttons with

hardness of 172 VPN were obtained, and there was a considerable decrease

in metallic and ncr-rsetnllio impurity levels, except for nitrogen.

The pellets sintered at 11OO°C were also used.in eleotro-

refining studies* Using a NaCl-NaF, HfCl. molt, optimum conditions

were establlohed to achieve maximum ourrmt efficiency and product

yield. A melt containing 4«5£ soluble hafnium, operated at 860°C was

found 8ULtable* With an ini t ia l cathode current density of 72 amp/ft

maximum cathode currant efficiency of 75$ and average product yield of

60% were achieved. The product was found to be low in Interetltlals

(126 ppm Ont 10 ppn Ng ; arc melted button hardness ISO VPN).

2.5 THORIUM

(C.V. Sundaram, J.G. Sehra and P.L. Vijay)

The studies on the preparation of ductile thorium metal by

magnesium reduction of ThCl. followed by pyrovacuum treatment wers

completed. The operntlng parameters for the production of ThCl^ from

thorium oxalate, purification of ThCl4> reduction of ThCl^ and vacuum

distillation of Mg find MgCl^ were establlshsi, and tho metsl snalysedl

847 ppm 0, 20 ppm H, 179 ppm C, 100 ppm Mg, 49 ppm Ps, < 5 0 pp« lfi,

11 ppm Alt 7 ppm Cr (arc melted button hardness t 90 VFIf).

2.6 TITANIUM

2*6.1 Treatment of llmenite with TiCl,

(Ch. Srldhar Rao and K. SwaaLnathan)

Experimental investigations on treatment of i lnen l t e ('Q1

grade) with TiCl. aimed at the preparation of a beneflciated product

and to understand the kinet ics of the process in the fluidlsed bed

reaotor systems were continued* Experiments were carried out on 10 g

scale In a s i l i c a tube reactor* The influence of reaction temperature*

gas flow rate* TiCl. concentration and duration of treatment on the

removal of iron oxides was studied.

In the temperature range (775-1OOO°c), I t was observed thatthere was a marked change in the reaction rate at 900°C. The reactionwas moderate in the temperature range 775-900°C and the activationenergy was estimated at 21 K.cal/mole. At higher temperature (875-1000*C) the reaction was found to prooeed at a fes ter rate and theactivation energy was estimated at 66 K.cal/mole. The difference i nthe reaction rates was attributed to the presence of PeCl, which hashigher vapour pressure at and above 900°C. In the high temperatureregion the conversion of iron ( 1 - ( i -x)T3 ) Vs time ( t ) relationshipwas found to be l inear t i l l 95$ conversion.

In the experiment on the effect of flow rate of t o t a l gat

(argon and TiCl, vapours)* I t was found that maximum conversion oeeur-

red at 3000 cc/mLn. From the studies on the effect of i n i t i a l concen-

trat ion of TiCl. i t was observed that the reaction follows f i r s t order

oheaLoal reaction* Further studies are being continued on the t r e a t -

t of oxidised ilmenlte with

2 .6 .2 Ifagnesiothermlo Reduction of Hutile i n HydrogenAtmosphere( j .C . Sehra. 1*0* Sharma and A. Unnikrishnan)

A programs aimed at the production of pure titanium fromdlreot reduction of r u t i l e followed by electro-refining of the metalwas in i t ia ted* Experiments were carried out to reduce ru t i l e with

magnesium In a closed vessel f i l led with hydrogen under a positivepressure of 20-30 cm of Hg.

500 gm of rutile nixed with magnesium (5, 10• 20% excess

orer theoretical) and MgCl2 (20, 30, 40 vt% ruti le) was kept in a

retort and f i l led with hydrogen gas. The retort was heated to 1000*0

and held at this temperature for 2-4 hours* At the end of the pre-

deteroLned period the product was removed and leached with d l l . acid

solution. In a typical run lasting orer 4 hours with excess Mg and

appropriate amount of MgCl2* metal powder with 90$ yield was obtained*

The product metal powder was compacted at 250 kg/cm pressurei n the form of pellets and sintered at 1100*C under vacuum (0.03 aioronpressure)* The sintered pellets were used as anode feed in the electro-refining process* The dlectro-refinlng was carried out at 850*0 inKaOl-TiClg melt with 3% soluble Ti at different current densities. I twas observed that a maximum current efficiency of 40$ was aefcievod at acathode current density of 360 amp/ft •

2*6.3 Fused Salt Electrolysis of TiCl4

(Ch. Sridhar Rao, T.K. Mukherjee* C* Subramanian and

K. SwartLnatban)

Investigations on the preparation of titanium metal fros.

TiOl, by i t s electrolysis in a fused NaCl-KCl melt were continued* A

few experiments were carried out at 780-800°C for a duration of 11 hrs*

at the Faraday/mole ratio of 6*5 and cathode current density of

400 amp/ft • The metal yield was low (40$?) and the arc-melted button

hardness 320 VPN. The failure to achieve good product quality and

yield was attributed to disintegration of graphite anodes and their

frequent failure in the operations*

2.6.4 Ferro-titanlum

(D.K. Bose and O.K. Mehra)

ferro-tltanium with 20 to 40^ Ti finds application in s t s s l

industry In the preparation of alloys* Experiments were carried out

to prepare ferro-titanium contacting 35$ Ti from llmenlte by openaluminothermic reduction process. The effect of Al content 0-20$•xcess over theoretical requirement, the l ive flux content (50-80$ wtof llmeniie) on ferro-titanlum yield and quality was studied. In atypical run with 200 gm iJjnenite with 180 g F e

2 ° v 15° 8° A1 o0*120 gm CaO, a well separated button of ferro-titaoium was obtained*at 90% recovery of titanium value*

2.6.5 Oxidation of FeCl- Aqueous Solution forProcessing Ilmenite

(Ch. Srldhar Rao, C Subramanian and K. Swaainathan)

solution which i s obtained by oxidation of Fe&2 i s

used in beneficintion of minerals. A potential application of ferric

chloride i s in the aqueous processing of ilmenite for i t s beneficia-

t ion.

For the experimental studies* a thick walled glass tube

50 mm dia» 1500 mm long was used ae the main reactor• An electric

resistance heating tape was used to heat the tube. The tube was kept

• t an angle (5*) to the horizontal to permit flow of the liquid* The

tube, the storage tank and the receiver tanks were pressurised with

oxygen gas to a desired pressure.

250 ml of FeCl solution containing about 25 gm dissolvediron was passed through the tube for each run. The effects of liquidflew rate (3*125, 5, 7*0 co/min), pressure (40, 60, 80 psig) and numberof passes (or duration) at the reactor wall temperature of 14O-15O°Cwere studied. The effect of in i t ia l pH (0.5, 1.5 and 2.5) of the solu-tion and i t s variation after each treatment was also followed. Theconversion was estimated by chemical analysis both for ferro content andtotal iron content after each proceeding stage.

The results indicated that pressure and flow rate but not pH

had marked effect on conversion of FeClg. Further studies art being

carried out to attain better conversions, especially with the half of

catalyst like CaClg, NH^Cl.

10

2.7 VANADIUM

I n v e s t i g a t i o n s on the development of processes for t h e

recovery of vanadium v a l u e s from i n d u s t r i a l byproducts l i k e ( i ) BayerB

s ludge , and ( i i ) vanadiferous s l a g were cont inued.

2.7.1 Treatment of Bayers Sludge

(CK. Gupta, P.K. Bose and O.K. Mehra)

The Bayers sludge used in these investigations was received

from M/s Hindustan Aluminium Company, Henukoot, U.P. Two alternative

hydrometallurgical processes were established to recover vanadium

values either as pure V O,- or a complex calcium salt of vanadium. Yet

another method was studied. In this process the sludge was dissolved

In hot water (70-80°c) with the addition of HgSO. to maintain the pH

of the solution at 7/8. The neutral vanadium rich solution was treated

with NH.C1 at room temperature to precipitate ammonium metavanadate,

which on calcination at 4?0*c resulted in pure V_0_ . T h e product was

analysed to contain about

2.7.2 Treatment of Vanadiferous Slag

(CK. Gupta, D.K. Bose and O.K. Mehra)

Vanadiferoua slag - a byproduct in the processing of t i tani-

ferous magnetites at M/s VTSL, Bhadravati was used in these studies*

The slag was treated both by pyro and hydrometallurgical methods to

recover vanadium values.

The process involved salt roasting of the slag followed by

i t s leaching to dissolve the vanadium content. Salt roasting experi-

ments were carried out in a rotary kiln. The effect of roasting

temperature (6OO-9OO°c), amount of salt-soda ash (10.205? by wt* of

slag)} duration of roasting (0.5 to 3 hrs.)> presence of an oxidising

agent (KC10,) and the particle size (-60 +325 mesh) on vanadium

recovery was studied.

It wae observed that slag size of -100 mesh, 20% sod* ash,

556 KC10, in the charge and roasting at temperature of 800*0 for a

period of 2 hours were optinum conditions for 98$ vanadium recoveries.

11

2.7.3 Production of Vanadium Oxycarbide andi t s Evaluation as Steel Additive

(CK* Gupta and D.K. Bose)

The suitability of vanadium oxycarbide as an alternative to

vanadium carbide and ferro-ranadium as a steel additiTe was investiga-

ted.

Vanadium oxycarbide was prepared by controlled reduction of

VgO- with petroleum coke. V20_ and petroleum coke powders were nixed

and compacted to pellets. The pellets were heated to 1300*0 in an

electric resistance furnace* and held at ultimate raeuun of 500 torr.

Tho product obtained was found to be corresponding to

•mpirical formula, voo.67-o,44 °< ,2-0.7 * Sucii R Produc1; w a * **••*

as a steel additive. The quality of the steel obtained were compared

with those obtained by the addition of vanadium carbide or ferro-

•anadiua. Vanadium recoveries and solution times for a l l the vanadlua

additives were found almost similar* With vanadium carbide there was

some pick up of carbon in the Bteel* as contrasted with vanadium oxy-

carbide from which carbon pick up was practically negligible*

2.8 NICKEL

(C*K. Gupta* T.K. Itukherjee and P.P. Shukla)

Investigations on recovery of nickel and copper values from

a sulphide concentrate (6$Ni, S$Cu. 20#Fe) supplied by the Uranium

Corporation of India Ltd* were continued* Salt roasting and wet

chlorine treatment processes were studied*

2.8.1 Salt Roasting Process

The salt roasting process which was established on 50 gm

scale of the concentrate in static bed glass reactor was reexamined in

rotary kilns in £ kg batches. The major problem encountered In operat-

ing such a furnace was caking and sticking of the charge to the furnaoe

wall leading to incomplete roasting. This problem was however solved

by incorporating in the charge steel balls or rods which helped in

12

milling the agglomerated charge in the free-flowing powdery form.

Efforts were also made to conduct the roasting in a specially

deesigned roaster* The roaster essentially consisted of a horizonta-

l l y placed stationary mild steel reactor provided with a centrally

placed baffled shaft to serve as a raker. This modified design was

found satisfactory in conducting roasting operations.

A fresh batch of higher grade concentrate analysing 7«O6$li.

17.8$Cu and 3O#Fe was alao processed by the salt roasting technique by

varying the salt to concentrate ratio from 1 to 0.12. It was found

possible to recover 93$! of the nickel and 97$ of the copper with nickel

to iron ratio of 3.82 by using a salt to concentrate ratio of 0.5*

2.8.2 Chlorine Leaching

Detailed investigations were carried out to establish aqueous'dor' nation as a possible route for the processing of the sulphide

concentrate. The process in brief consisted of passing elementalohlorine at ambient pressure in an agitated aqueous slurry of theconcentrate*

The effects of pulp density (5 to 33 wt#), leaching tempera-

ture (25 to 100°C), amount of chlorine (1.25 to 4.56 gm per gm of the

concentrate) and i t s rate of passing (40 to 160 co/mln) on nickel

recovery were studied. It was found possible to recover 98$ of the

nickel and 72% of the copper value present in the concentrate by using

• pulp density of 28$, a temperature of 60*0 and 3 gm of ohlorine per

gm of the concentrate, passed at a rate of 80 cc/ndn. The leach solu-

t ion was however found heavily contaminated with iron as about 70£ of

the iron got solubilized to a remedial measure* the concentrate was

pre-roasted at different temperature (450 to 700»c) in a rotary furnace

before chlorine leaching.

In comparison to the direct leach, roasting at 450°C followedby Clg leaching required 75% less chlorine, the recoveries of nickeland copper were almost quantitative and the nickel-copper bearing solu-tion was very low in iron.

In a variation of the process, efforts were also made to avoid

roasting step by adopting a two stage Clj-Og leaching procedure. In

this new technique chlorine leaching of the sulphide was accomplished at

40 pal pressure and temperature of 90 to 150°C in a glass-lined steel

reactor to solubilize nickelt copper and iron followed by oxymixtures at

same temperature and pressure to precipitate iron as hydrated iron oxide*

The solution i s under evaluation.

2.9 RARE EARTH - COBALT PERMANENT MAGNETS

Rare earth - cobalt permanent magnets of the R(COL type made

of binary a l l o y s of cobalt with cerium, samarium, preseodymium etc* are

known t o possess maximum energy products (BH) • These magnets a r e

used as a i rcra f t and aerospace instrument components. Optimisation of

d i f f e r e n t routes for the production of Ce-Co and misch metal-Co a l l o y

powders was carried out*

2.9.1 Direct Alloying Method

(T.S. Krishnan and R.F. Tangri)

The constituent components that i s cerium and cobalt were arc-

melted or induction melted in an alumina crucible and cast to ingots*

The alloy obtained by these two melting methods were found to contain

undesirable phases (RgCOe / R2Goi7 ) instead of wholly R(Co)_ phase.

The castings were crushed to powder and separated into separate size

fractions. The powders of specific size fraction were compacted in a

magnetic field and the magnetic properties were studied* Bffeot of

particle size on the magnetic properties of the product was studied*

The Ce-Co alloy obtained by induction melting and casting

was crushed to 10-15 micron size powder. The powder was pressed in

6 kOe field* The product material was found to give magnetic induction

(Br) and coercivity H_ value of > 1000 G and >1000 0Q respectively*

further studies on high field pressing followed by annealing and

remegnetisation of the compacts are being explored*

14

Reduction-diffusion Process

(T.S. Krlshnan, P.R. Menon and R.P. Tangri)

Development of the reduction diffusion process, a relatively

economic route for the preparation of rare earth - cobalt magnetic

material was investigated.

A charge consisting of cobalt and rare earth oxides were

co-reduced with calcium metal in hydrogen gas atmosphere? to prepare

R(OoL type alloys* Influence of parameters like charge composition,

particle size of constituents materials, reduction temperature, duration

(reduction / diffusion) e t c , on the product yield and the nature

(composition/phase) of the product was studied• A charge consisting of

rare earth oxide and 25/6 excess calcium was compacted at 30 ts l and

heated to 1200°C The reduction was carried out at this temperature

for two hours• The reduced mass was leached and evaluated. Alloy

powder with 95$ yield rich in R(CoL phase was obtained.

2.10 METAL POWDERS

Sub-micron and micron s i z e metal powders are u s e f u l i n making

high density sintered compacts. Investigations were carried out to

prepare fine size Mo and W powders by hydrogen reduction of their

oxides and oxychlorides*

2.10.1 Molybdenum

(C.K. Gupta, T.K. Mukherjee and P.V.S. Pi.lai)

Pure molybdenum oxychloride was prepared by low temperature

(300°c) oxychlorination of molybdenum concentrate. The oxychloride was

distilled in a pyrex reboiler and was allowed to pass through a silica

tube reactor. Hydrogen gas was also admitted into this tube. Number

cyclone type of condensers and collectors were used to receive the metal

powder. It was also possible to develop the metal coating on surfaces

by this method.

In a typical run, molybdenum oxychloride was distilled at the

rate of 30 gm/hr and passed through the reactor tube held at 900*C and

15

reduction carried out by passing 300 cc/mln of hydrogen* Submlcron

alze molybdenum metal powder was obtained.

400 gm of high purity molybdenum powder was also prepared by

hydrogen reduction of molybdic oxLde at 1000°C In an externally heated

reactor tube.

2.10.2 Tungsten

(T.K. Mukherjee and P.P. Sbukla)

Chemical precipitation was investigated to prepare subnrVcron

size tungsten powder. In the chemical precipitation technique a satu-

rated solution of ammonium tungstate was slowly added to , H nitric

acid which was kept stirring. The precipitate was filtered, dried

and calcined to obtain tungstic acid which was reduced with hydrogen

at 750*C. The powder (-400 mesh) i s under evaluation.

2.11 THERMOCHLMCAL AND THERMODTOAKtC STUDIES

2 . 1 1 . 1 Refining Tantalum by Carbon Deoxldationand Sacrificial Deoxldation

(S.P* Oarg, N. Krlshnamoorthy and R. Venkataramani)

The relative extent of carbon deoxldation (as CO) and sacrif i-

c ial deoxidation (as TaO) was investigated with a view to purify tantalum

metal with respect to oxygen impurity.

Tantalum powder containing 5OOO-6OOO ppm oxygen was mixed with

required amount of carbon and pelletised. The pellets were heated to

high temperatures in an Induction furnace under vacuum. The effect of

temperature (165O-2O5O°C), order of vacuum (1.5 x 10 5 x 10*5 torr

pressure), oxygen to carbon ratio (1.0 - 1.5) and duration (1-4 houre)

on the extent of deoxidation was studied. The samples were analysed at

various stages for their oxygen and carbon contents.

It was observed'that temperature and pressure have great

effect and substantial deoxidation occurred only above 1800°C at

1.5 x 10 - 5 x 1O~P torr pressure. It was also observed that oxygen

was f irst recovered as CO t i l l the carbon content was 300 ppm and then

sacrificial deoxldation occurred. In a typical run carried out at 205O*C

16

with O/O ratio 1.05, 5 x 10"5 torr pressure for 2 hours, a product

containing 100 ppm carbon and 200 ppm oxygen was obcoined with

negligible loss of metal values*

2*11*2 High Temperature Reaction between ffluO-t NbC and TIC

(S.P. Garg, N. Krishnamoorthy and R. Tenkataramani)

The study of reaction between Nb^O., NbC and TIC as per theequation

^ Nbg05 + (5 - x) / 5 NbC + £ TIC « ^ m>7-a Tix + CO

was continued* It was aimed to investigate the titanium deoxLdationtendency in Nb and also to prepare Nb-Ti alloys*

Pellets of the components containing oxygen/carbon ratio1 .01 t 1.1 and titanium content of 5 to 50 atm % were heated upto1900*0 i n an induction furnace under vacuum (10 torr) and then meltedin electron beam furnace to obtain buttons.

It was observed that near complete removal of titanium and

oxygen occurred during the reaction stage irrespective of i n i t i a l charge

composition. Oxygen was removed mainly as TiO/ \ x 0 (g) with no loss

of niobium. When Ti content was more than 15 atom % TiO evaporation

rate was found higher than CO thus resulting in a product richer in

carbon. In a typical run with 0/C ratio 1.05 and 5 atom % Ti, a

product (Kb) containing < 1000 ppm C, 300 ppm 0. and 800 ppm residual

Ti was obtained. It was concluded that Nb-Ti alloy could not be

prepared, though purification of Nb with respect to oxygen due to eva-

poration of TiO could be achieved.

2*11*3 Preparation of Uranium Silicidea andThermodynamic Properties of USi-(S.P. Garg and Y.J* Bhatt)

Uranium forms a number of important refractory compounds 031,USi2 , U-Sie , USi , U_Si2 and U-Si with sil icon which are of interestto the atonic energy programme. Preparation of these compounds by

17

sllloothermic reduction of UP. and thermodynanlc studies of USi, hare

therefore been investigated.

A mixture of UP. and sil icon ponder was charged in a tantalus

crucible and heated at a constant heating rate of 6°C/min under vacuum

in a vacuum thermoanalyser. The thermogravimetric and the differential

theimogravimetric analyses indicated that the reaction proceeds in the

following sequence s

4 UP,, + Si *» 4 UP, + SiP,4 •* 5 4

4 UP, + 15 Si 4 USi, + 3 S1P4 . . . . . ( i l )

4 U*3 + 11 USij » 15 US12 + 3 SiP4 . . . ( l i i )

4 UPj + 29 USi2 N 11 U3Si5 + 3 Si?4 . . . (iv)

The last step upto the U,S:U stage (reaction iv) goes to completion on

~2 —5

holding the charge at 95O°C under vacuum (10 to 10 p torr) . The

preparation of lower s i l ic ides (US1> U^Sip and U,Si) by this process

would require heating the charge further above 1000*C and has not been

attempted as UP, i t s e l f has an appreciable pressure above this tempera-

ture. Thus only the s i l ic ides USi, to U-Si- can be prepared by this

prooess-

The standard free energy change of the reaction ( i i ) has

been determined by the measurement of equilibrium pressure of SiFj(g)

over the mixture of UP, + Si + USi, employing static method of vapour

pressure measurements* Prom these measured values and from the

reported free energy of formation of UB_(s) and SiP.(g) the standard

free energy of formation of USi,(s) has been calculated between 870 to

1040°K and can bt represented as- - 32470 + 0.50 1 cals / mole

4

18

These investigations were carried out in collaboration with

Shri D.D. Sood and Stall Rajendra Frasad of Radio Chemistry Division.

2.11 Thermodynamic Studies of 10 by Isopiestic Technique

A programme was initiated to investigate the thermodynamlc

properties of WC by an isopiestic technique. The method involved the

equilibration of a mixture of WC and tungsten with pui« iron pieces

sealed in a quartz capsule containing trace amount of hydrogen. The

equilibrium was achieved through the following reversible reaction*

C. (in WC or Fe) + ^ • - *• CH4

Since the activity of carbon in the WC + W mixture and in iron wil l be

same, the activity of carbon in the (we + W) mixture was determined

from the carbon content of iron at equilibrium. The free energy of

formation of WC ( AG$C ) was determined making use of the concentration-

act ivi ty relationship for dilute Pe-C alloy available from the l i t era -

ture. From experiments carried out at 1196 and 1302 K, the AG£_

values were estimated as -7270 and 6860 cal/mole respectively. Further

work i s under progress*

2*12 STUDIES ON PiUIDISED BED SYSTEMS

(Ch. Sridhar Rao and D. Sathiyamoorthy)

Fluidieed bed systems, particularly of the eolid-gas type,

can be used for physical operations and for carrying out chemical

reactions of metallurgical interest . Studies were undertaken on the

design of gas distributors in gas-solid fluidised beds. A theoretical

model to design the multiorifice plate gas distributors was proposed.

Experimental investigations were carried out to establish the design

equation.

Experiments were carried out in a 100 ran dia(c) glass tube

assembly, consisting of 20 ( N ) , 3 mm dia orif ice holes* Oas flow

(compressed air) through each orifice was noted by means of orifice

meters incorporated in each distributor orifice l i n e . Total a ir flow

19

(U) and pressure drops across the bed (BP 6) and the distributor (BPd)

were noted* Zircon, rutile and alumina powders were used as bed

material* The number of operating orifices (n) with respect to air

flow rate (O-Umf-UM) and bed height (1 to 7D) were recorded.

Equations of the following type were derived :

v* " Jf U-Umf » K !

where K and KO are system dependent and system-independent constants*A PdMethods for predicting KO and . -. were also proposed • Fron the

experimental results, validity of the above equations was proved and

values of KO were determined for each set of experimental conditions*

Least square values were determined for al l the set of experiments

under N = N condition which resulted in an equation of the form

Thus having known the APd/AFb rate for a system U,, and finally

the APd and the orifice plate could be designed. Based on these

studies a gas distributor for a high temperature process Is being

designed*

2*13 DEVELOPMENT OF PLASMA FURNACE

(T.K. Mukherjeo and 3 . Nanda)

A programme was i n i t i a t e d t o develop a plasma furnace which

could generate temperatures of 2000°C. Such furnaces are use fu l i n

the beneficiation of ores and extraction of metalo*

A laboratory scale induct!on-coupled-plasma furnace using

argon gas was designed and fabricated* The furnace consisted of a

37 ma dia x 600 mm long transparent s i l ica tube. An induction coil

was wound round the tube. R.F. power supply was used to generate the

heat. Argon gas supply ports and material feed ports were provided at

the top end of the s i l ica tube. A 200 mm long water cooled assembly,

at the lower end of the tube formed the produot collector* Blank test

20

rune were carried out ana the temperatures of the order of 2000°c were

achieved* Further work on treatment of ores and minerals i s in progress*

2.14 BERYLLIUM PILOT PLANT PROJECT

(CV. Sundarara, CM. Paul, B.P. Sharma and K.S. Subbarao)

2.14.1 Project Report

The Departments of Electronics and Space have emphasised the

need for the se t t ing up of an indigenous f a c i l i t y for the production of

copper-beryllium a l l o y s and beryllium metal at an early da te . Extensive

demand surveys carried out by various groups have placed the present

annual requirements at about 10 tonnes of copper-S^beryllium a l loy and

250 kg of beryllium metal . Accordingly a project report was prepared*

i n June) 1917, for the se t t ing up of H P i l o t Plant to produce 10 tonnes

of copper-2^beryllium a l loy ingots and 250 kg of vacuum hot pressed(VHP)

beryllium per year blocks i n s ing le s h i f t operation. (The Plant could

be operated i n 5 s h i f t s when the'demand increases . The June, 1977 Pro-

j e c t Report was prepared on the premise that the P i lo t Plant w i l l be se t

up at the new BARC s i t e at Vashi (New Bombay), an an independent f a c i -

l i t y having i t s own electric substation and other ancillary fac i l i t i e s*

The June '77 Project Report has formed the basis for a Memo-randum of Understanding between the Departments of Atomic Biergy, Elec-tronics and Space. It has been decided that the Pilot Plant wil l beengineered, erected, commissioned and operated by BARC personnel and thenecessary capital and operating funds wi l l be provided by the Depart-ments of electronics and Space. The financial sanctions for the projecthave been received from DOS and D0T5.

2.14.2 Civil, Electrical and Ventilation Works

Based on the preliminary equipment layout drawings and elec-

tr ical and ventilation requirements finalised by the Beryllium Project

group, tender drawings for c iv i l , electrical and ventilation works for

the Beryllium Pilot Plant were prepared by the Civil Engineering and

Technical Services Divisions*

21

2.14«3 Procurement of Jiquipment and Materialsand Recruitment of Staff

Indents for materials required in advance for fabrication

of equipment and for long delivery items were raised. PurchnRe orders

for the supply of stainless steel materials were released. Specifica-

tions for other equipment were detailed* Action was also initiated

for the recruitment of staff urgently required for the project.

2.14*4 Conversion of Copper-Beryllium Alloy Ingots

Whereas the Beryllium Pilot Plant will produce cast bery-llium-coppei alloys in the form of 15 kg ingots, for end applicationsin the electrical and electronic industri es these alloys would befinally required mostly in the form of thin fo i l s and sheets and tosome extent as wires and rods. It has been suggested that since thequantities of coppe r-beryllium alloyc produced annually are relative-ly small, i t would be better to entrust the conversion of ingots tothe final shapes, to other organisations which have the necessarycapability and capacity.

In the above context a meeting was held with the members

of the Advisory Council, from the Department of Electronics, the

Beryllium Project group and ty/s Bralco Metal Industries, Bombay,

(one of the leading producers of sheets and fo i l s of copper and copper

base alloye in India) in September 1977 to discuss on the conversion

of copper-beryllium alloy ingots to finished shapes and to formulate

basis*for further negotiations on the terms and conditions of contract*

It was decided at the meeting to roll some test ingots, at M/s Braloo'a

rolling fac i l i ty , in order to standardise the various rolling para-

meters. Work was accordingly initiated to study the hot and cold ro l l -

ing of copper-beryllium. Twenty kilogram ingots of Cu-2#Be alloy,

(210 mm x 160 mm x 65 mm thick) were successfully cold rolled at 75O°C

to 6 and 10 mm thick strips. The stripe have been annealed and scalped

preparatory to further cold rolling.

22

2»14»5 Copper-Beryllium Alloys - Demand Survey

In order to obtain a fresh compilation of information, regard-

ing the quant i ty requirements and deta i led technica l spec i f ica t ions of

copper-beryllium a l loys required by the ac tual u se r s , a comprehensive

standard format was prepared and c i rcula ted to the users through IPAG

(Elect ronics Commission)* The compilation of the r e s u l t s of t h i s

market survey w i l l provide a bas is for r a t i o n a l i s i n g the var ious spec i -

f i c a t i o n s of copper-beryllium a l loys i n to a small number of standard

spec i f i ca t ions t ha t w i l l be acceptable to the majority of the users«

The compilation wi l l a l so provide the bas is for holding discussions

with organisa t ions which are l i ke ly to be entrusted with the conversion

of t h e a l loy i n g o t s , produced i n the P i lo t Plant , t o var ious finished

forms*

2.15 PROCESS DEVEIOPMENT

2.15.1 Preparat ion of Anhydrous Beryllium Fluoridefrom Indian Beryl

(CM. Paul, K.S. Subbarao and S.A. Kullcarnl)

About 1000 kg of beryl lumps have been ground to -200 mesh by

bal l milling, operated in close circui t with rake c l a s s i f i e r .

Studies have been continued on the si l ico-fluoride sintering

of beryl for conversion of beryllium values of beryl in to water soluble

form on a 500 g BeO scale . I t has been found that by sintering at

75O*C for 2 hours followed by water leaching of the wet ground s in ter ,

with a water to solid ra t io of about 3 : 1 , about 97$ of the beryllium

values of beryl could be recovered in the water soluble sodium bery-

llium fluoride.

Preparation of beryllium hydroxide by sodium hydroxide t r e a t -

sent of BOdium beryllium fluoride leach liquor followed by f i l t r a t ion

i n a s ta inless s tee l plate and frame f i l t e r press has been studied on

a 150 g BeO scale and the overall beryIlium recovery has been observed

to be around 97.5$. In another experiment beryllium oxide having a

purity as high as 99$ has been successfully prepared on a 150 g soale

by precipitating sodium beryllium fluoride leatch liquor (5.5 g BeO

per litre) with 20^ MaOH solution. The hydroxide was first dried at

200°C and then calcined at 900°G.

Studies have also been carried out on the recovery of

fluorine values from the filtrate containing NaF, obtained in the

filtration of Be(0H)2- It has been found that pH has a profound

influence on the recovery. The fluorine recoveries have been found

to be 91% and 96$ in the case of Fe2(S04) and FeCl, respectively at

a pH of 5.

Based on the earlier operational experience on the decompo-

sition of ammonium beryllium fluoride, a modified decomposition

assembly consisting of a nichrome wound resistance furnace, inclined

graphite decomposition tube, stainless steel screw feeder and water

cooled nickel condenser was designed, fabricated and commisRioned*

The assembly has the capacity to produce 500 g BeP-/hour. The decom-

position zone of the inclined graphite tube is maintained at a tempera-

ture of 900°0. Ammonium beryllium fluoride is introduced progressively

with the help of e. screw feeder through a tube passing through the

nickel condenser. Molten beryllium fluoride which flows out through a

hole at the bottom of the inclined graphite tube is collected in a

graphite mould. With this system it has been possible to prepare BeP_

with a recovery of about 95',$.

fc.i5»2 Preparation of Beryllium and Copper-Beryllium Alloys

(CM. Paul, B.P. Sharma, V.D. Shah and M.G. Rajadhyaksha)

A silica tube vacuum induction melting unit was designed and

fabricated for vacuum melting beryllium pebbles. The silica tube is

flanged at both ends and sealed with neoprene gaskets. The system is

evacuated through the bottom flange with a combination of oil diffu-

sion pump and a rotary pump, while the top flange supports a view port*

Beryllium is melted in a beryllia crucible by indirect induction

heating using a graphite crucible as a susceptor, and is allowed to

solidify in the crucible itself. V/ith this assembly beryllium pebble*

24

hare been melted and purified on a scale of 250 gra, under a dynamicvacuum of 10 torr at a recovery of 92%*

Preliminary designs of a vacuum Induction melting and t i l tpouring furnace, with a effective crucible volume of about 1.7 l i t re s ,for the purification of* beryllium pebbl.es and a vacuum hot pressingUnit for fabrication of 100 mm dia x 100 mm long beryllium blocks havebeen completed•

About 40 kg of copper-beryllium master alloys containing

about 8.5$ Be have been prepared in 5 and 6 kg batches at a beryllium

recovery of about 85#. The reduction of BeP2 (25$ excess over theore-

t ica l ) was carried out at about 1000°C for 2 hours with magnesium-in

the presence of copper* The final temperature of the charge was

brought to 1400°0 to effect better slag metal separation. The master

alloy was cast in graphite moulds* The BeF, present in the slag was

recovered by water leaching*

Cu-2#Be and Cu-0.7#Be alloys were prepared by diluting the

master alloy with appropriate amount of copper in a induction melting

furnace* Casting recovery and soundness of cast could be considerably

Improved by reducing the shrinkage pipe by improving the mould tundish

design* While casting a slab of 160 mm x 65 mm cross section, the

Shrinkage pipe could be almost completely eliminated by maintaining a

tundish hole diameter of 8 ran and by preheating the tundiah to 450CC

with the help of blow torches •

In response to a request from VSSC, Trivandrum about 100 kg

of Cu-0*5$Be - 2.7$C0 alloy ingots have been supplied.

About 25 cast b i l l e t s of Cu-2#Be and Cu-0.7#Be, each weigh-ing about 3 kg, have been hot extruded at 75O°C, at Atomic Fuels Divi-sion, to 27 and 37 ran diameter rods, after proper solution treatmentand machining. Limited quantities of these rods ware supplied toM/si Escrots, New Delhi. M/s FeeVee Precision Works. Madras, and toCombat Vehicles Research and Development Establishment, Avadi inresponse to their urgent requirements*

25

3. PHYSICAL METALLURGY

Physical Metallurgy Section continues to pursue basic studies

in physical, mechanical and structural properties of metals and alloys

of interest to the nuclear energy technology. One important aspect

that is emphasised is the understanding of the structure-property corre-

lation in many of the systems.

Basic investigations on the deformation behaviour of zirconium

and zirconium-o3<ygen with respect to grain size and temperature of de-

formation have been conducted. A potential pressure vessel steel is

being evaluated for various mechanical properties so as to ascertain

its usefulness in as-reactor material applied problems such as diffusion

bonding, and pressure bonding techniques are being studied to evolve

suitable methods for making composite plates.

Phase transformation studies and influence of structure on the

mechanical properties, utilising transmission and. scanning electron

microscopy and inntron testing machines have-been made. A large volume

of interesting data on a number of binary and ternary systems of

zirconium based and titanium based alloys, have been collected

A general theory of transformation structure is emerging from

these studies which would enable one to predict may useful alloy systems

for Bpecial applications.

Diffusion studies, involving intrinsic and interdiffusion pheno-

menon have been continued and valuable datqihave been collected. Analysis

of these data have led to the generalization of the theory of diffusion

in metals in general and zirconium in particular. Ii^adiation and its

influence on mechanical properties on metals and alloys has been continued

with a view to understand the defect generation, annihilation as reflected

in the gross property changes.

Physical Metallurgy Section has been rendering service to various

organizations regarding failure analysis, metallographic evaluation of

structural components, alloy making etc.. The Section has also undertaken

many an applied problem of interest to the nuclear energy programme,.

26

3 . 1 MECHANICAL METALLURGY

3 . 1 . 1 Deformation Behaviour of Zirconium Alloys

( i ) The Influence of Deformation Twins on the Tensile Propertiesof Zirconiura-2.5vrt#Nb Alloys

(M.K.Asuirii, T.K. Sinha and J.K. Chakravarthy)

It has been observed in zirconium and zircaloy-2, that the

occurrence of a small volume fraction of twins by low temperature

deformation, improved both the strength and the ductility of the

material, deformed at room temperature. The objective of the present

programme was to study the influence of the deformation twins on the

tensile properties of zirconium-2.5^ niobium alloys.

In order to study the twinning behaviour, it was necessaryto develop a well-defined grain size in the specimens by suitableheat-treatments• A heat-treatment schedule of vacuum annealingat 85OfC for 5 hrs, was selected. Microstruotures of the annealedsamples consisted of equiaxed oC grains of about 44/Asize andtransformed fi> grains having Widmannstatten type morphology. Tensiletests were carried out at 77 K-300 K at nominal strain rates of10"^ to 10~ min" . The occurrenoe of twins were evident from thesharp load drops in the load-elongation diagrajn and the audibletwin cry associated with twin initiation. The initiation of twinswas found to be accompanied with very rapid work-hardening rate.The presence of twins was further oonfixmed by the optical micros-copy using a nod is ing etching techniques. It was noted that theoccurrenoe of twins was strongly dependent on temperature and strainrate but deformation twins did not embrittle the material as wasevidenced from the duotility values and the SEM examinations of thefractured surfaces. TEtt work is in progress to study the twinningcharacteristics which will enable more meaningful correlation ofmechanical properties with types of twin present*

( i i ) The Deformation Twinning Behaviour of Zirconium-Oxygen

Alloys

(V.Raman, T.K. Sinha and M.K. Aaundi)

The objective of this work was to study the influence

of interstit ial elemejt (oxygen) and the grain size on the deforma-

tion twinning behaviour of zirconium. Zirconium-oxygen alloys con-

taining 100-1600 ppm of oxygen and grain sizes varying from 5yU- to

75/A-were tested under compression at temperatures varying from 77 to

296. K and using a nominal strain rate of 10 rain.~ . Twinning wai

observed only at an intermediate range of grain sizes varying between

15*25 yU » and only in alloys containing 300 to 600 ppm of oxygen.

The results are being analysed to correlate the deformation twinning

behaviour with composition and grain s ize , by determining the twinning

frequenoy and nature of twins, by metallqgraphio techniques.

( i l l ) Studies on structure-property correlation in a zirconium-

4.6 wt$ aluminium alloy

(V.Raman, P. Mukhopadhyay and S. Banerjee)

Attempts were made to correlate the earlier reported•trengthening of Zr-4.6wt^Al alloy with mlcrostructures in the lightof the existing theories of alloy hardening. In order to explainthe strength of beta quenched alloy, theories of solid eolationhardening were utilised to calculate the approximate yield stress*The high strength of the alloy treated at the lower temperature(650*C)could be explained in terms of the contribution from the cohere icystrains associated with the state of order within the tnetastableparticles. The strengthening contributions due to the lamellar oC -Zrand Zr,Al were analysed on the basis of Ashby's theory of plasticallyinhomogensous materials and the calculated strengths compared favour-ably with the observed strength. The strength of the alloy was found

28

to decrease appreciably with increasing thlckrasB of the Beoond

phase lamellae. Tlie work hardening behaviour was analysed on

the basis of Ashby's work hardening theory.

It is proposed to study the temperature and strain ratedependence of this alloy in three heat treated conditions.

(iv) Grain Siao Effe'cts in Zifconiura-Qxygen Alloy*

(V. Raman and P. Dasgupta)

. - The Hall-Fetch slope for Zr-0 alloys with 100 to 1600 ppo

oxygen and 'jAX - 15 U grain size as a function of strain (Kfe )was found to show peaks in the curves. These maxima occurred atlower plastic strains in low oxygen al loys, while higher oxygenalloys manifested these at higier plastic strains. The plots ofK& vs tt> for the 800 ppm alloy at room temperature showed acontinuous decrease while that of friction stress $i against dp

showed a monotonio increase. This trend waB more pronounced atlower temperatures. The variations of <5~~0 and Kfc with oxygencontent exhibited both maxima and a minima at some levels of oxygen.The above findings were rationalised in the light of the modelsavailable for grain size effects and strengthening.

(v) Structure and Strength of Dilute Zirconium-CopperMartensites(S.L. Wadekar, V. Baman and F. Mukhopadhyay)

The morphology, the substructure and the strength of

dilute zirconium-copper martensites were examined. The mart ens i te

obtained on rapidly quenching the alloys from the beta phase fields

was found to have a, lath morphology and a dislocated substructure.

Precipitation at the lath boundaries oould hot be suppressed by

this quenching treatment. These precipitates did not have the

stoiohlometry of the equilibrium ZrgCu. The strength of these

marteneiteB was found to increase substantially with inoreaaing

29

additions of copper. This strengthening was due both to solidsolution hardening and to the distribution of precipitates atthe lath boundaries. The work hardening of dilute ziroonium-oopper martensitee could be analysed in terms of Ashby'B theoryof tht deformation of plastically inhomogeneous materials. Thetemperature dependence ot the flow stress at any given level ofplastic strain indicated that the addition of copper enhanced

mainly the a thermal component of the flow stress.i

J.1.2 lleohanical Properties of a Prospective Reactor VesselSteel of ASM Designation HY-130(T.K. Siriha, J.K. Chafcrabarthy and M.K. Asundi)

This research project was undertaken to study the influenceof microstruoture on the flow and fracture behaviour of a potentialnuclear pressure vessel s teel ; a low carbon alloy s t e l l of 5 Ni-Cr-Mo-Vtype.

The available literature shows that this steel possesses anexoellent combination of properties such as high strength, hightmghMMi good weldability and hardenability through a thicknessof 4". In addition, this steel in querched and tempered condition^has not only init ial low IDT, but also very low radiation enhanced

mn shift.Two ingots of the nominal composition 5# Ni, O.57»Gr, O.5Jt Mo,

0»52&in, 0 Afi V and O.13J&C, and balance Pe, were prepared by vacuuminduction melting. Microstruoture of the cast ingota showed fairlyhomogeneous dendritic structure and the hardness of oast ingotB were260 ± 10 Vfrl. Although this steel shared high work-hardenabilityand a 2$f» cold reduction increased hardness from 260 to 310 TPI •i t showed Batisfaotory hot workability and could be hot-rolled intostrips of 1 00 thickness, from a hot-forged ingot of 30 x 25 x 150 ansic*. Micrcmtructure of hot worked strip appeared to to bainitloin nature.

30

The influence of beat-treatment* on the structure has beenstudied* While annealed samples showed a hardness ralue of270-290 YPN, both the quenched and the normalised (Air cooled fromaustenitising temperatures) samples resulted in the hardness ralliesin the range of 400-430 VPN, indicating the air hardening character-i s t i c s of this steel in rery thin sections* The adLcrostructurein the quenched normalised conditions, appeared to be martenaitioand/or bainltic in nature and that of annealed ones, appeared to betransformed carbide or iatermetallic phases distributed mostlyat the grain boundaries and id thin the prior austenlte grains*

The tempering bebariour of this steel has been studied

to evaluate both the effects of time and temperature on the hardness

raluea and the microstructures* Martenaitically transformed speci-

mens were tempered in the temperature range of 300-700°C (at an

interral of 100*c) and the tempering times of 1 hr and 2 hrs. at

each temperature. Tempering response has been studied both by the

plot of hardness rariation with temperatures at rarious times

as well as by the plot of hardness values against Hollman-Jaffee

parameters* These results indicated that the material possesses

good tempering resistance although there was no eridence of secondary

hardening in the high temperature region. Transmission electron

microscopic work i s in progress to correlate microstructures with

these obserratlons• Exhaustire experimentation i s also underway

to correlate tensi le , stress rupture and impact toughness properties

with mlorostructures of this material*

3.1*3 Solid State Welding of Zircaloy-2 Slates(V. Raman, R. Kishore, J.K. Chakrararthy and M*K. Asucdi)

( i ) Pressure Welding of Zircaloy-2

Modifications were carried out on an existing equipment usedfor pressure welding runs* These were necessary in order to controlaccurately the different parameters in bonding experiments*

31

Experiments were conducted varying the temperaturethe pressure applied, and the time of application of pressurein a systematic way. The zircaloy-2 plates, used in theseexperiments were 25 ran square coupons, 0.5 mro thick. Thesurface of the coupon^ wma polished slice i t i s known that thesurface condition of the zircaloy has e. significant influenceon the bond quality.

Trial experiments indicated the following conditionsto b» suitable for effecting a good bonding between two testplatesi

Temperature - 85O°C ; Pressure 200 psi andTims t 50 ains.

This condition was based on metall©graphic examination of thesectioned pieces, which showed that the grains were continuousacross the origiral interface,

( i i ) Eutectic Diffusion BondingEuteotic diffusion bonding has teen reported to be an

inexpensive method with the possibility of achieving high bondstrength. This process involves the formation of a molten eutecticlayer of zirconium and a bonding agent such as copper between thezircaloy surfaces to be joined and the subsequent diffusion ofthe eutectic forming elements until the zircaloy matrix Is conti-nuous across the bond interface.

Experiments were carried out to establish the feasibilityof this technique as a method for fabricating plate type fuelelements. The effects of various fabrication parameters on thebonded samples were looked into. The fuel element* samples com-prised three basic components - sircaloy receptacle plates, coversheets aid fuel-wafers containing uranium-dioxide. Fabricationprocedures included plating of the receptacle plates with thebond log agent and coating of the fuel with a barrier material toprevent the reaction between the fuel and the clad. A procedureto dip-plate copper on sircaloy-2 was standardised. It wae found

that an oxidising treatment preceding the dip facilitated the

development of a thin (O.SyU. ) adherent uniform film on the

reooptacle plates. Some experiments were also conducted

employing graphite powder as a terrier material between the fuel

and the zircaloy plates to inhibit reaction between then. On

the basis of these experiments, it was possible to establish

the following optimum parameters for eutectio diffusion bonding

of zircaloy-2.

TemperaturePressure

1000°C25 psi

Time of application

of pressure

Thick ness of

bonding agent

the

£The application of pressure

is necessary only to ensure

intimate contact between a l l

oonponents ]

' 15-20 minutes

t 0.5 microns

These experimental conditions permitted excellent bonding

between the plates and the complete disappearance of copper at

the interface, presumably by diffusion into the bulk. The experi-

ments were conducted on J" x 3" samples.

Efforts to quantify such results and determine the strength

of the bond are underway. Hadiographic examination of the elements

ia also being done to evaluate the integrity of fuel pellets after

the bonding operation. 5\iel-clad interactions are also being

studied.

( i i i ) Gas Pressure Bonding

An equipment has been fabricated and one tr ial run taken

for the gas pressure bonding of large size (12" x 6") fuel eleaients.

Such a procedure has all the advantages of an isoetatic method.

33

J.I .4 A flew Method for the Evaluation of Internal Stress fromStress-Strain Transient(V.V. Raman and Ji.K. Asundi)

The methods hitherto in use for the determination of

internal streBB in materials were handicapped from certain limita-

t ions, either from the scope of validity of assumptions or from

the experimental shortcomings. In order to avoid the handicaps,

a now method was developed which i s free from the assumptions

except those which are the most general and the most widely

accepted. The only experimental requirement 1B a tensile testing

machine with which the specimen can be loaded continuously at a

constant extension rate.

The present method define a a variable T =• £ |»/£b whereii s the plastic strain and 6 b i t s differential with respect totine during the stress-strain transient. It can be shown that

T» 0 when the applied stress equals to internal stress, Froma plot of log £ u against log t b one can find the slope atvarious points. A function F - 1/1- • . ^ ^ can te evaluatedfor various points for which the values will also be different.

When T • 0, F wil l be equal to 2.0. The integral / FdT giveso

the tine during which the specimen has been undergoing plastio

defomation. From this the internal stresB can be evaluated.

In Zr-2.5^Nb this method was used and the result waa

compared with the om obtained by incremental unloading. The

value obtained by the present method is much lower than the one

obtained from incremental unloading* This is in accordance with

the observations in published literature, where after correction

for machine relaxation the value i s muoh lower than the om eva-

lua-ted without correction.

34

3.2 STRUCTURAL METALLURGY

3.2.1 Phase Transformations in Zirconium Alloys

(i) Active Eutectoid Decomposition in Near-Euteetoid Zirconium-

Copper AlloyB

(P. Kukhopadhyay, S.S.K. Menon, S. Banerjee and R. Krishnan)

In continuation of the work mentioned in an earlier report,

the decomposition of the beta phase and tho consequent formation of

the intermetallic Zr?Cu phase (MOS1 2 structure) in a Zr-1.6i»t^Cu alloy

has been examined in detail. It has been observed that eutectoid de-

composition occura very rapidly and cannot be suppressed even by fast

beta quenching. The quenched structure consists of a lamellar

aggregate of the alpha phase and a partially ordered, body centred

cubic, metastable phase. The correspondence between the parent beta

and the product alpha lattices is the same as that observed in tho

martensitio beta to oC reaction in zirconium alloys. There exists

an one to one correspondence between the beta and the metastable

phases. It has b een possible to propose a mechanism for this active

eutectoid decomposition on the basis of the crystallographio and the

microstructural datajSbtained from this study. The reaction appears

to be a hybrid of martensitio and diffusion controlled processes.

The metastable phase has been found to attain the structure and the

stoichiometry of the equilibrium Zr_Cu phase on tempering the beta

quenched alloy. The orientation relationship between the equilibrium

eutectoid products is t

(0001)^

T100"[

35

( i i ) Precipitation of ZrCr2 in a Zr-1.9 rtjiCr Alloy

(P. iukhopadhyay, V. Ranan, S.J.Vijayakar and S.Iknerjee)

The precipitation of the topologically close packed

Laves phase ?<rC!r2 (Mg Cu2 structure) in a martensitic matrix

has been examined in this alloy. The roartensi+° fomed on beta

quenching has a plate morphology and a dislocated substructure.

Jfeighbom-ing martens ite crystals are often twin related, the

twin plane being the | iof i] type. The precipitation of 2rCr2

precipitates cannot be suppressed by rapid beta quenching.

Tempering at lew temperatures givjs rise to a bi'nodal precipitate

size distribution. A significant amount of precipitate coarsen-

ing occurs on ageing the beta quenched alloy at 7OO°G. During

tempering at this temperature, the raartensite undergoes reecv«ry

and recrystalliestion, the shapes of the recryetallised grains

bsing determined by the distribution of heterogenGOusly nucleated

ZrCr_ precipitates fevmed during beta quenching and durinr; the

early staeen of agsir'S' The orientation relationship between

the alpha ard the 2rCr2 phases has been established as s

foooi} // {011}

( i i i ) lilartensitic and Preciyitation Reactions in a 2r-

Alloy

(E.G.K. Menon, P. Mukhopadhyay and S. Banerjee)

Tlie raartonsite produced on beta quenching this alloy lias

been found to have an internally twinned plate morphology, th*

twinnirg being on the [1O11? planes. Arrays of dislocations

lyixg alorg these planes have also been observed anl i t appears

that in addition to the {1011^ twinning shear, a slip shear on

a different variant of the £ 10i"i| plams i s operative as an

inhomogeneous shear system during the martenBitio transformation.Depending on the ageing temperature, two different precipitationsequences have been encounterad while tempering the beta quenchedalloy. At temperature's lower than the monotectoid but not farbelow i t , the metastahle, zirconiun-rlch /£>* -phase precipitatesin the «<'matrix. At s t i l l lower temperatures, the equilibrium,tantalum-rich 6 . - precipitates emerge. Preferred sites forprecipitate nucleation are the interfaces associated with the•artensite structure s plate and twin boundaries. These observedprecipitation sequences have been rationalised in terms of the freeenergy versus composition plots generated from the analysis of the•irooniua-tantalum phase diagram. The orientation relation betweentht oC and the &j phases has been found to be i

(0001)*

(lv) Hiase Transformation Sequences in Zlxconium-Iiobium

and Zirconium-Tantalum Systems

(E.S.K.Menon, F. Mukhopadhyay, S. Banerjee and

R. Krishnan)

Making use of computed free energy versus compos it ionplots of the alpha and the beta phases in the binary monotectoidzirconium-niobium and zirconium-tantalum systems, the possiblesequences of phase reactions in binary alloys of any given composi-tion have- been worked out.

In zirconium-rich alloys, where ket* quenching leadsto the nartensitic transformation, the supersaturated aarteistte(denoted by «<' ) decomposes during tempering through one of thefollowing routes t

1. aC ><+l$x—• <* + /3JJ ,whtnthe

ageing temperature i s lower than but close

37

to the monotectoid temperature(Tm) and the solute conoentration,

X, in the c<' phase ie less than Xo , the concentration at which

the free energy ourves for theidpha and the beta phases intersect.

when the ageing temperature Is lower than but close to IJQ and X

is greater than Xo.

3. *t * «when the ageing temperature is ouch below Tffl.

In wore concentrated alloys where the beta phase i sstabilised, the decomposition of the beta phase follows one ofthe following sequences*

1. p—> l*i+fin,when the ageing temporal; ire is higher than Tm.

2. / 3 _ _ > i S I + /3D • < * « f ^ f f _ _ > . < + ^ n j

when the ageing temperature is below Ta and in the range where the

omega phase is unstable; <<* comes directly from fbj and contains

much more eoluto than the equilibrium alpha phaee.

3. p > ftz+Ps > U>+P>E > «+P&jwhen the ageing teoiperature is below TQ and is in the range where

the omega phase i s metastable•

The phase separation reaction [&—* fri + Pji oouldocour either through a spinodal mechanism or through a heterogeneousprecipitation process, depending on whether the ageing treatment iscarried out inside or outside the coherent epinodal.

3*2.2 Ehase Transformations in Commercial Titanium Alloys

The influence of microstructura on the mechanicalproperties of several heat-treatable coraneroial titanium alloyshas been studied with a view to examining the importance ofdifferent phase reactions in strengthening these alloys. Both<* + &

and t& alloys have been selected for this work and the results

obtained with some of these are summarised below.

( i ) Precipitation of Widmanstatten Alpha in the Ti-6Al-2Sa-42r-6 Mo Alloy(M. Mohan Rao and S. Banerjee)

It i s known that several mechanical properties, parti-cularly fracture toughness and tensile ductil ity, are stronglyinfluenced by the shape of the alpha grains in °C + S titaniumalloys. In industrial practice, the oontrol over the grain shapeis achieved through a proper choice of the final fabrication step*When this temperature 1B in the beta region, the alpha phase preci-pitates4 in the form of .Vidnanstatten plates when the alloy i scooled after fabrication. On the other hanii, when the finishingtemperature l i e s in theaC-t/J.field, a distribution of equiaxed alphaand beta grains i s produced. - The mechanism of Widmanstatten alphaprecipitation in the Tl-6Al-2Sn-4Zr-6i«lo alloy has been studied here.

It has been found that a tfidmanstatten alpha plate ismade up of several finely divided alpha crystals, often twin relatedwith each otter. The twinning system has been observed to be of the

{1012]^ type. Many of the alpha plates are constituted of a mono-l i thic core enveloped by a layer of finely divided, contiguous alphacrystals having orientations that are approximately twin relatedwith respect +0 that of the core. In the isothermally transformedsamples, many instances have been found where the alpha orystalsdo not satisfy the Burger's orientation relation.

Quenching the alloy from the beta region produces an orthor-hoabic martens it e which reverts back t o the parent beta phase duringelectrolytic thinning of the quenched alloy. Samples quenched fromthe oC + /3> field after allowing the separation of primary alpha havebeen found to consist of a mixture of the primary alpha end the orthor-hombic martensite phases.

39

( i i ) Effect of Heat Treatments on the Mechanical Properties

of the Ti-8Al-1Mo-1V Alloy

(S.J.Vijayalarfc S. Banerjee and R. Krishnan)

The influence

tionising temperature

of several heat treatment variables (e .g . , solu-

, duration and temperatn-e of tempering after

quenching) on the mechanical properties of i&e tear alpha Ti-8Al-1Mo-1V

alloy has been examined. The microstructuies developed in the alloy

after different heat treatments have been characterised by transmission

electron microscopy ahd the changes in the mechanical properties

have been correlated with the observed structures. Depending on

the heat treatment conditions, various microstruetural constituents

like the primary o< phase, the ordered oC« phase, the martenaitio

0<'phase, and the untransfozmed fb phaBe with a fine dispersion

of *O particles have been seen t o be produced in this alloy* These

constituent phases evolve through different types of phase reactions

such as , Widmanstatten precipitation, ordering, nartensitio reaction

and omega transformation. The characteristics of each of the Be

reactions, in relation t o the Ti-8Al-1Mo-1V alloy have been studied.

It has been found that the primary alpha phase in the

alloy* quenched from 750-850*C, undergoes a stress induced re>

orientation during deformation. This results in a considerable

fragmentation of the alpha grains. TheBe treatments correspond

to relatively low values of yield stress and Young's modulus,

suggesting that the stress induced reorientatlon-occurs within

the "apparent e last ic deformation" of the samples tested. Solu-

tionising in the Icmoi+B region appears to bs responsible for

the attainrent of a critical aluminium enrichment of the alpha

phase so that this phase becomes susceptible to the stress induced

reorientation procesB.

40

( i i i ) Influence of Qnega and Alpha Precipitation on

the Mechanical Properties of a Ti--15y&Io Alloy

(Una Maik, G.B. Prasad and S. Banerjee)

The influence of the precipitation of the cmega and the

alpha phases on the flow and fracture behaviour of a Ti-15J&Io alloy

has been examined. In this alloy the beta phase could be retained

at room temperature in a metastable form on beta quenching. On

subsequent ageing in the temperature range 3OO-7OO°0, the omega and

the alpha phases precipitate at lower and higher temperatures res-

pectively. The atherael omega phase is present even in the as-

quenched alloy* Mechanical testing of samples containing either

atherraal or aged cmega, in the range 250-350°C, shows a serrated

flow behaviour, the average load drop corresponding to each serra-

tion aril the critical plastic strain for the onset of serration

being determined by the temperature of testing and the strain rate.

In samples aged to form the equilibrium aC-tji structure, however,

serrated flow is not observed during testing at the same tempera-

tureB. This implies that in this alloy, serrated flow is connected

with omega precipitation during deformation at 25O-550°G - a tempera-

ture range where omega formation i s favoured.

The ductility of the alloy deteriorates drastically with

the emergence of increasing amounts of the omega phase. A remarkable

change in fracture morphology - from microvoid coalescence to

cleavage fracture - accompanies this drop in ductil ity. It has also

been noticed that extensive omega precipitation causes intergranular

fracture with steps on the grain boundary facets.

3.2.3 Phase Transformations in Copper Alloys Precipitation

( i ) Precipitation in Dilute Copper-Beryllium Alloys

(E.G. Baburaj, U.S. Kulkarni, E.S.K. Menon and R.Krishnan)

In view of the interest of the department in oopper-

beryllium alloys, the age hardening response of a binary Cu-1.77

41

and a ternary Cu-1.75wt# Be-0.6 wt Co alloy has bem examinedin detail . Structural oharacterieation of these alloys indifferent heat treated conditions has been carried out usingoptical, X-zay and electron metallography. Die influence ofheat treatment variables on the mechanical properties of thesealloys has also been investigated.

An examination of the sequence of precipitation inthese alloys has shown that the emergence of the equilibriumCuBe phase (B2 structure) is preceded by a pre-precipitationphenomenon in which solute rich clusters are formed. The strainsassociated with such compositional fluctuations have been foundto be reflected in the observed asymmetry in X-ray diffractionpeaks and also in the appearance of a "tweed" contrast in electronmicrographs. The streaking of electron diffraction spots alongt h e O 0 0 ^ and the <"11O^ directions in the reciprocal spacehas lent further support to this contention. X-ray diffractionhas also shown the presence of a superlattice reflection whichcould be indexed as the { 100] peak of a beryllium rich meta-etable phase having the LI structure* On progressive ageing thissuperlattice peak shifts gradually to the low angle side andfinally attains the £1OO£ peak position of the equilibriumCuBo phase. From theee observations it could be concluded tnatduring ageing at low temperatures, precipitation occurred throughthe simultaneous operation of the continuous ordering and thespinodal. clustering processes. '-Phis is accompanied by a gradualreduction of the axial ratio of the tetragonal unit ce l l to afinal value of .unity (corresponding to the equilibrium B2 struc-ture ) .

With the addition of cobalt, the reaction has been

found to be accelerated and hus it is easier to follow the

sequence of the reaction in the ternary al loy. In addition, the

42

prewnce of cobalt in the alloy has been observed to restrict

the grain growth during the solutionising treatment. This

results in an enhancecnent in the strength of the ternary alloy

viE-a-vis the binary alloy.

Correlation of microstructure and mechanical properties

suggested that in theee alloys the peak hardness and strength

are associated with a micrestructure consisting of a fine dis-

persion of CuBe (32 structuxe) precipitates in the matrix. The

pre-precipitation stages correspond to gradually increasing

strength levels with increasing ageing time. The overage ing

process results in a growth of the precipitates and a consequent

drop in the strength levels.

( i i ) Precipitation in a Cu-8.02 M-6.12 Sn Alloy

(E.G. Baburaj, TT.J). Kulkarni, E.S.K. Menon and S.Banerjee)

The precipitation sequence in a ternary Cu-8.82 Ni-6.12 Sn

alloy has teen investigated in view of the attractive combination

of strength and ductility in this alloy. The decomposition of the

supersaturated solid solution has been found to initiate through

a spinodal mechanism. At a later stage of ageing discontinuous

precipitation has been observed to occur and the resulting duplex

cells have been seen to grow at the expense of the spinodally

decomposed matrix. These cells are composed cf the supersaturation-

relieved alpha phase an3 an intermetallic (Cu,Wi)5Sri phase (JXL

structure). The influence of these miercetructures on the

mechanical properties of the alloy has been examined. It has

also bee*, found that peak strength could be achieved here or.

ageing for veiv- short periods.

3.2.4 Structural Characteristics of Internetallic Hisses with

Lip and DO..,.. Structures

(H.G.K. i'femn and P. i.'Iukhopadhyay)

The hard sphare 'nodel, with its inherent assumption of

43

atonic lnoompressibility, is used extensively in describingcrystal structures. However, it i s believed that the applica-bility of this model i s rather limited while dealing withmetallic materials where the atone appear to be readily compressi-ble. The extent of validity of the assumption of incompressibilityof atone has been tested, in relation to the totality of the inter-met all io phases having the Llg and the DO..Q structures, by compar-ing the reported lattice parameters with those obtained on thebasis of hard sphere model calculations.

In the case of the U, phases, a plot of the calculatedvalues (a*) of the lattice parameter against the reportedvalues (a) could be fitted to the straight line a* - 1.07a-0.25,which is very close to the ideal a* * a straight line in theregion of interest. It has also been seen that for most ofthese phases the a1 value l ies well within + 5j£ of the a value.It follows, therefore, that the atoms constituting these phasesare not compressed touch and that the description of the £&„structure in terns of a close packing of cannon ball atoas la notunreasonable. A similar conclusion has been arrived at with regardto the DO1(j phases though the deviation from the hard spherebehaviour is somewhat more marked in this case.

The values of the space filling factor, in the case ofthe lip phases, have been found to fchcw a considerable scatter.However, both the arithmetic mean and the node of the distributionl ie between 0.75 and 0.60. This corresponds to a slightly betterspace filling than that obtained in the A., structure and pointsto a slight compression of the constituent atoms.

3»2.5 Texture Studies(C.H. Rao an) Lai it Kumar)The effect of aluminium additions on the rolling

structure of titanium las been examined. It has been found thatthe basal poles tend to orient closer to the normal direction

44

as the aluminium concentration increases.

Texture inhoraogeneity in rolled zircaloy sheets has been

studied with theaid of basal pole figures and normal axial pole

figures obtaiied from d ifferent sections (from the top surface

to the mid plane) of tb* sheets. The basal poles have teen found

to rotate towards the transverse direction in the surface layers

indicating the presence of larger shear forces on the surface

as compared to the interior during rolling*

An investigation on the anisotropy of thermal expansionand of yield strength In rolled zircaloy sheets i s in progress.The results are being correlated to the texture in the materialby using the axial pole figure. 3he method involves the evalua-tion of the BAEP by combining two or more pole figures which axeobtained from x-ray diffraction data associated with threeorthogonal surfaces. By appropriate stereographic transformations,the x-ray data -ire transformed to correspond to any desired set ofreference directions and the resulting pole figures, in tarn,are util ised t o evaluate the texture density in the BAPF. ThisBAEF would directly yield the axial pole figure correspondingt o the new normal direction. Thus the axes transformation forthe BAPF is achieved indirectly by f irst transforming the x-raydata.

Fortran programmes based on this procedure have been

developed far analysing the texture anisotropy in hexagonal

materials.

5.2.6 Irradiation Induced Effects

(it. Sundararanan, S. Banerjee and R. Krishnan)

Irradiation induced void formation in alloys is stronglyinfluenced by microstructure, the important aicroetructural para-meters being the dislocation dereity and the nature, density anddistribution of second phase precipitates. %e effect of coherent

precipitates on void swelling has been examined using the

generally accepted model of void foraation which assumes that

void embryos /rrow under a condition where equal nunbsr of

vacancies and interst i t ialB are continuously generated by the

incident radiation but interst it ia Is aze preferentially absorbed

in some sinks present in the material. The elastic strain fields

associated with these coherent precipitates would Interact with

those due to vacancies and interstit Jals and this would result

in the trapping of these defects. This elastic interaction has

been evaluated for two specific t^peB of coherency strain f ield*.

It has been shown that the elast ic interaction between the

strain fields due to a precipitate and a point defeot reduoea

to zero when the stress free strain associated with the preci-

pitation process can be described as an isotropic dilatation.

In such a situation there would not be any preferential attraction

towards any specific type of point defect and thus the precipitate

interfaces can be considered as variable biased sinks as has bean

assumed in the analysis due to Bullou$i and Brailsford. However*

for other types of strain configurations, this assumption would not

be valid.

3 .2 .7 Production of Ultrafine fetal Powders by the Jreete Drying

Technique

(Laiit Kumar, V.K. Sasidharan, R.Krishmn and M.K.Asundl)

The freeze drying technique has been used for the

produotion of ultrafine nickel powder. A fine strean of an aqueous

solution of nickel formate is introduced into a cryogenic aedlua

(e.g. liquid nitrogen) where it freeze* in the fora of snail

globules. These globules are separated froa the cryogenic aedium

and are immediately dehydrated in thn solid state under a dynamic

vaouuni at a suitable temperatures, taking care that melting does

not oocur during the process. The dehydrated residue consist* offin*

an amorphous aggregate of^particles of the solute. The amorphous

46

nature of this aggregate has been established by X-ray diffrac-tion. Decomposition of the dehydrated nickel formate i s carriedout at a suitable temperature ( w-, 280°c) in a hydrogen atmosphereto yield an ultrafine nickel powder, crystalline in nature.Electron microscopy has shown that these particles are sphericalin shape and 800-1000A0 in size. Efforts are being made to educethe particle siae further and to increase the yield of tile metallicpowder.

3.3 METAL PHYSICS

3.3.1 Solid State Diffusion - Metallic Systems(B.D. Sharma, G.P. Tiwari, S.K. Khera, G.B. Kale, R.V. Pat i l ,and V.V. Utgl)

(a) Self-diffusion in Dilute Zr-Fe and Zr-Cr Alloys

Self- and solute diffusion studies in dilute alloys areessential to understand the rate controlling diffusion mechanism.This i s particularly important for the controversial case of diffusionin Zr alloys in b.c .c . phase. Ihe temperature dependence of tileself-diffusivity in a series of Zr-Fe and Zr-Cr alloys representedby Arrhenius relationship i s l isted below:

Table t 1 : Diffusion Parameters in J2> -Zr, Zr-Fe andZr-Cr Alloys in 900-1250 °C Temperature Range

Composition „( a t $ Tracer Do , IT S"1 Q, KJ. Mol"1

/3 -Zr Zrff 6.8 x 10"f 145 + 8j&-Zr Be3* 4.4x10"' 116.95

Zr-0.98 Fe Zr£"? 6.33 x 10"7. 166 +8.2Zr-1.35 Fe Zr~ 2.08 x 10~' 150.9 + 13-4Zr-1.64 Fe Zj%> 1.62x10"' 145.9+7.2Zr-3.54 Fe Ztf£ 2.9 x 10"' 140.9 +7.2Zr-6.37 Fe Zr w p 5.16x10"^ 183.0+10.0

Zr-2.0 Cr Zr^ 5.16 x 10"I 165.2+7.5Zr-3.5 Cr Ziqc 2.0i> x 10"£ 169 Jt 8.7Zr-4.1 Cr Zryp 1.39 x 10"° 169 + 4 - 5Zr-7.86Cr Zr^5 1 .59x1O" 6 1 7 3 + 2 . 6

47

The above diffusion data shows a negative value of corre-lation factor (-3O<>7 to -16.7) in 9OO-12OO*C temperature range fordiffusion of Pe in £ -Zr. For the diffusion of Cr in P> -Zrthe correlation factor values is more reasonable. The implicationof negative correlation faotor i s being examined on theoreticalbasis . This programme of tracer diffusion i s being extended toother alloys of interest like Nb-Zr system.

(b) Chemical Diffusion in Multiphase Binary Systems

The kinetics of nucleation and growth of intermediatephases in multiphase binary couples are controlled by several factorssuch as interdiffusion coefficients, homogeneity range and heat offormation of the phases, crystal structures of adjacent phases, andtheir nelting points etc. Evaluation of diffusion data i s , however,intimately related to establishment of accurate concentration-penetration profiles by EPMA, identification of various phases, and

analysis of concentration-penetration profiles in conformity tostandard solutions. Interdiffusion studies on Fe-Ti and Th-Fe binarysystems have been continued to understand the problems involved.

The concentration-penetration profiles of Fe-Ti couplesdiffusion annealed in 89O-1O5O*C temperature range, are marked byabsence of Pe-Ti and FeJPi phases despite prolonged annealing. Thetemperature and conposition dependence of interdiffusivity intitanium and iron-rich side of this system, can be written as,

CTi

105 exp (-7 5 .7 Cpe) exp

„ * I WO- I I^» , | _£«-1

where Q is in KJ/mol and C™., C_ are concentration in at#.

Absence of intermediate phases probably Arises due to the relative

flux of atoms moving across the phase boundary interface.

48

In the case of Th-Fe system, sandwich type diffusion

couples have been annealed in 37O-IO4OK temperature range and

concentration-penetration profiles established by EPMA. Ihese

couples exhibited a time and temperature dependent growth of

BuPe, phase, and another one of a composition close to 50 at#

The concentration profiles of diffusion zones showed that the

latter phase grew at the expense of Th-Fe, phase. As no near

eutectic composition (45 at$Fe) intermetallic phase is reported

in the phase diagram, the diffusion zone either represents a

transient condition or characterises possibility of modification of

phase diagram by lowering of eutectic temperature. The average

dif fusivities in the phases have been evaluated by applying

Heumann's analysis and these can he represented by

LFe-rich

D1h-rich = 1 # 1 5 x 1 ° 4 1 e x p (-

where Q i s expressed in KJ mol" . The diffusion couples also pro-vided ample evidence of the brittle nature of diffusion zones. Workon several other points of interest is being continued.

(c) Interdif fusion in Binary and Ternary Solid Solutions

Interdiffusion problems in binary and ternary solid solu-tions besides the atomic mobilities of diffusing species is alsocontrolled by vacancy winds effects. Because of this the diffusionof faster diffusing sp#ole«is enhanced and that of slower ones isretarded. A programme to study interdiffusion and intrinsic diffu-sion coefficients in ternary solid solution of Fe-Cr-Ni systemhas been initiated. Suitable alloys for these studies have beenmelted - and it is proposed to investigate the composition depend-ence of diffusion profiles/paths as also the influence of vacancybehaviour.

49

The influence of • vacancy wind' effect in diffusion

kinetics of several solid solutions recently investigated e.g.

Fe-Al, Ti-V, Pe-V systems etc., is also being re-examined.

Possibility of undertaking thcrmomigration studies in

alloys of interest employing EPM/^analytical techniques la also

being planned.

3 .3»2 Mass Transport in Nuclear Ceramic Oxides

(1.D.9»XM, D.D.Dj*4hj*y* ax*

Mass transport in ceramic materials occurs through the

migration of cation and anion vacancies, and 1he behaviour of

these defects is the key to the understanding of the sintering

mechanism. A programme of research pertaining to cation tracer

diffusion, and chemical diffusion in mixed oxide system with

emphasis on ThO_ has been finalised, and will be taken up shortly.

3.5.3 Hadiation Damage Studies

(B.D. Sharma, G.F. Tiwari, I.S. Batra and M.N. Vijayakumar)

(a) Diffusipn Reactions during Post-Irradiation Studies

The annealing behaviour of neutron irradiated zircaloy-2,

nickel-titanium alloys etc. has been investigated in theitast, using

changes in the strength parameters. These changes are not sensitive

to point defects and the diffusion reactions arising due to migration

of these defects. Presently, tiprograntne to establish a post-

irradkiation laboratory with capability of handling resistivity

measurements upto liquid He temperatures is in the planning stage.

In the meantime, initial work on nickel alloy making, specimen fabri-

cation and specially designed specimen holders etc. is in progress.

It is also proposed to employ positron annihilation techniques

for this kind of investigations.

50

(b) Mechanical Properties of Neutron Irradiated Hard hep

Metals and Alloys

Radiation hardening studies on hard hep metals and alloys

have been continued. A series of investigations on neutron-irradiated

commercial cC -titanium has been completed. Sheet specimens of sponge

purity titanium (oxygen content <~ 1400 ppra) in o£ -annealed condi-

tion with an average grain size of 20yU were neutron Irradiated in

APSARA reactor to different integrated flux levels. Both annealed

and neutron-irradiated specimens were tensile tested to examinef the

8train rate sensitivity in 77-373K temperature range and also to

determine the internal stress by the stress-relaxation technique.

Present studies on hard hep metals Zr and Ti, have confirmed

the rate controlling deformation mechanism to be due to Peirels and

Nabarro below 200 K, and probably cross glide at higher temperatures.

Neutron irradiation of these metals of low interstitial content did

not alter.the low temperature mechanism, but, at higher temperatures,

increujed defect-dislocation interactions were observed. Yield point

phenomenon and work-hardening characteristics of these metals could be

rationalized in terms of dislocation dynamicB. In the case of commer-

cial purity metals, interstitial oxygen-dislocation interaction remained

the rate controlling.mechanism in the whole temperature range of

77-373K. Neutron irradiation did not cause any changes in the rate

controlling process.

(o) Radiation Hardening Studies in fcc/bcc Alloys

The irradiation - physical and mechanical property correlation

in several fee and bee solid solutions and two phase alloys la of

interest because of their likely application in different kind of

nuclear reactor systems. Of pai'ticular interest in this category

are some nickel, aluminium and niobium base alloys. In continuation

of the earlier studies on Nickel-Titanium alloy, a programme to study

51

solid solution and irradiation strengthening effects in Ni-V and

Nb-Zr alloys are being initiated. Literature survey has indi-

cated reduced radiation swelling in the two phase Ni-V alloys

and also probability of substantial microstructural changes during

Ions term neutron irradiation of Hb-Zr alloys due to traiMatatl«K

processes. Irradiation induced diffusion reactions in unsaturated

solid solutions lying eloae to a two phase boundary can also result

in the nucleation of precipitates. At present stage, appropriate

alloy compositions, which will be realistic to irradiation induced

effects are being finalised and are being taken up for melting

and fabrication.

3 .3.4 Studies of Inert Gases in Metals

(G.P. Tiwari and K.C. Paliwal)

Inert @as behaviour in metallic systems is of relevance to

structure-property correlation. Currently, two aspects, i ,e , (i)

nucleation and growtn of helium gas bubbles in copper-boron alloys

subjected to neutron irradiation, and (ii) gas release from then?

alloys during isochronel/isothermal annealing, have been in progress.

Hie role of spontaneous vacancy condensation on ;as bubbles contri-

buting to their growth, and consequently to swelling problem has

been examined by forming binary diffusion couples of irradiated

(Cu + B) alloy and nickel, ftie vacancy drift due to differential

atomic mobilities of Cu and Ni atoms, i s found to influence

growth of gas bubbles in the diffusion zones. Evidence to show

enhanced nucleation and growth of bubbles in the vicinity of free

surfaces - suggests that such surfaces act as sources of vacancies

which take part in the nucleation of helium gas bubbles.

The data concerning gas release from irradiated Cu-B

alloys - annealed to different tarfttlras in 400-1050*C tcapoxatuve

range, is being examined to arrive at quantitative conclusions.

A programme to investigate the mechanical properties of

inert gaw doped metals is also being planned employing suitable

nuclear reactions t and would be taken for detailed investiga-

tions in the coining year.

5 «5.5 Splat Cooling Studies

( P.K.K. Nayar)

Studies on splat cooled metals and alloys brue revealed

that the microstrueture of the matrix in these cases is dependent

on both the temperature of the melt and the substrate - besides

the substrate material* This is due to the fact that in liquid

quenching* the nearest neighbour configuration of atoms in the liquid

state itself provides the nucleation sites. Diffusion reactions in

splat cooled alloys do not exhibit enhanced diffusion effects -

as the free vacancies are usually 'agglomerated' into relatively

stable structures. In a recent investigation on Al-3.7#!u alloy

splat cooled from 900°C to liquid nitrogen temperaturet the

transformation kinetics of 9 phase formation has been exanined.

following resistivity techniques. Ageing of splat cooled alloy films

(20 /*. thick) at 175. 200. 250 and 300"C provided resistivity date

which could be expressed oy the usual fraction transfoxmed-time

relationship, i.e.

f « 1-exp

where K and n are Hie reaction constant and exponent respectivelyThe analysis of the data led to linear log In (i-f)~ vs log tplots with reaction exponent n - 1 *46. Activation energy deter-mined taking into account the incubation period for 0.156 phasetransformation, corresponded to a value of 26.6 Kcal/nole, ThisIs comparable to diffusion aotivation energy of Cu with AlThisfcuggests that short range diffusion of Cu atom is probablyresponsible for nucleation of 6 phase in this typt of aaiarLaj.SkInvestigation on Al-Sn *nd Al-Si alloys *• also in progress.

5.3.6 INSTRTOEKTATION

(P.K.K. Hajar and R.V. Pa t i l )

(a) A system -for flash heating and rapid quenching of metals

and alloys by employing condenser discharge pulse in the range of

10 amp at 50 volts B.C.- has been assembled! The system provides•7

for a heatinc rate of 10'K/sec. for 25yU thick foils, and aquenching rate of - iCrK/aec. Itio system has applications in splat

cooling, preparation of fine grained structure, and study of

different kinds of transformations.

(b) A low background, high resolution X-ray diffractometer

using Cu Krfj , radiation, double crystal monochromator, and double

crystal ftatlyatr has been designed to scan the range -7 *<£*©< 90*.

Die design provides for a temperature control in 77 to 600 K range.

She engineering designs of the apparatus axe being prepared at ttiis

stage.

(c) A preliminary survey to set up a R.P. or D.C. sputtering/

etching unit for diffusion studies has been made, and effort would

be made to set up this facility during the coming year.

3*5.7 Progress on R-5 Irradiation Facilities

(a) Planning

(B.D. Sharraa)

A report on Radiation Damage; Present status and future

perspectives- signifying the areas of current and future interests

with respect to both from baaio ani applied research points of

views has been prepared. The role of advanced research techniques

for post-irradiation research of different kinds has been individually

reviewed. R-5 irradiation facilities must be supported by adequate

poet-irradiation research laboratories with capabilities of handling

cryogenic experloents. Formation of several groups to undertake

and set up a tradition in resistivity and X-ray studies of irradiated

54

sample*, positron-annihilation studies* cyclotron irradiation

and related problems is planned. Initial work on organising

this aotivity has already been initiated - to begin with by

looking into procurement of hi^i sensitivity equipment for

resistivity studies of point defects in metallic systems.

(b) Low Temperature Irradiation Facility

(B.D.Sharma, P.K.K. Nayar, S.K. Khera and G.P.Tiwari)

A tentative design for R-5 low temperature irradiation

facility - providing for variable irradiation temperature

control of 20K and above, and facility for removal of irradiated

specimens, has been designed. It is proposed to employ compact

oryogenerators with cold^ielium gas as coolant for irradiation

capsules. To convert this tentative design to drawing reality,

numerous problems concerning cryogenics, heat loads - both nuclear

and conventional, radiation streaming and protection therefrom,

oryocapsule design and guidance system etc. are being considered.

Optimisation of heat load, and radiation protection are critical

areas in designing suoh equipments, and careful evaluation is

essential* and would be undertaken.

(o) tn-pile Creep/Corrosion Experiments

These experiments are in initial stages of planning*

55

4 . CORROSION AND BTECTHOMEPALIDlMHr

The a c t i v i t y of t h i s sec t ion comprises of research and

development wor't in the f i e l d s of corrosion and electrometal lurgy.

A good number of research programmes i s i n t e r d i sc ip l inary i n nature .

The corrosion group has continued i t s a c t i v i t i e s In studying

the high temperQtura corrosion behaviour of various materials of

in teres t t o nuclear programmes, corrosion ra te s of various material*

In sea and s a l t water appl icat ions and s t r e s s corrosion cracking of

austenl t i* s t e e l s n icke l base alloys, aid zirconium a l l o y s .

The electrometallurgy group has been engaged in studies on

electroplat ing of metals, a l l oys and composites, oleotroforming of

meshed products, electrowinning of copper and niokel by f ludidlsed bed

e l e c t r o l y s i s and eleotrophoretlo deposit ion of graphite and nicke l

oxide as wel l as studies on packed bed electrodes and electrowlnning

of rare earth n e t a l s .

The sect ion i s a lso engaged In offering consultancy services

t o the different uni t s of BAB i n solving various corrosion problems

In different p lants , rendering advice in materials se l ec t ion and

supplying electroplated components.

4.1 HIGH IBM3SRATURB COHHOSIOB AND OHDATIOi: STUDIES

4 . 1 . 1 . Blxeonlun a l loy development <

• ) Corrosion t e s t s on the experimental Zr-0.5 Mb - 1 Or a l loy

(H.S. Gadlyar)

In the sireonium al loy development programe, several binary and

ternary a l loys based on Ib and Or additions have been oorroeion t e s t ed

t o compare t h e i r behaviour with that observed with sircaloy - 2 . The

experimental a l l oy 2r - 0.5 Bb - 1 Cr wee found t o have oorroaion r a t e s

oomparable t o that of s irealoy - 2 In high purity, high temperature

(upto 36O*C) water and the rates were much lower In high temperature

(400-550*0) eteui, with added adrantage of lower hydrogen adaorptlon

than sircaloy-2 wider out of pile oonditlon*. Steam oorroeion tes t s

on this alloy hare been oontlnued*

Vhe 3 and 14 day ABOL specification test* In etean at400°C (1500 pel) were carried out. Two other experimental alloymt

namely Zr - 0*3 Fe - 1 Cr and Zr - 0.3 Fe - 1 Cu were also IncludedIn this t e s t . The weight gains obtained were considerably belowthe ABOL specified Tallies of 22 and 38 mg/dm2 indicating theirsatisfactory eorrosion resistance. Aaongst the three alloys tested,Zr - 0.3 Fe - 1 Cr showed the lowest weight gain.

b) Effect of Al, Ma and 1"2 as impurities In slrcaloy - 2 on i t seorrosion resistance.

(H.S. Gadlyar)

The 3 end 14 day tes t s carried out on several zircaloy - 2specimens with varying amounts of Al as impurity has shown that Alcontents upto 140 ppm have no significant effeot on the eorrosionrates of siroaloy - 2. This has been arrived at also by analysingthe data from several such studies reported in the literature. Asregards Impurity limits for I 2 and Mn, analysis of the data has notshown any detrimental effeot upto 118 and 290 ppm respective additions.The maximum apeolfied limits of Al, I 2 and 1th in siroaloy - 2 are 75,80 and 50 ppm respectively.

4*1.2. Effect of prefilm on the corrosion of siroaloy - 2 in hightemperature water(S.T* Ihadn:La, K.B. Oaonkar and H.S. Oadiyar)

Studies on iih« eorrosion of siroaloy - 2 in 35O°C doubledist i l led water at aai;uration pressure (2300 psl) have been continuedla the presenoe of preflima formed under different experimentaleondltlona. The pref liming conditions were t - 1) a t e « at 400*0,1900 pal i i ) water a* 30090, 1100 psi 111) oxygen at 600*0, 1atmosphere. Irefllm thickness i s about 1 micron. Prefllmlng la water

57

at 300*0 was found to gire weight gains Initially, upto a periodof 25 days. However, continued exposure upto 120 days have resultedIn lower weight gaine for specimens prefilaed in ovgtn. Averageweight gains of 45-6, 47*8, 58.6 ag/da were obeerred for epeolaenepreflined lnO,, steam and water respectively after 120 days ofexposure. Further long tent exposure to cb serre the extent ofhydrogen absorption on the coupons under these eauditions Is Inprogress.

4.1.3 Effect of surface chloride oontanination on the highteaperature oxidation of Ziroaloy - 2.(K. Blayaperuntl, H.S. Gadiyar and S.7. Ihadnis)

Studies have been initiated to see the effect of surfacechloride oontanination on the high tenperature oxidation of Ziroaloy-2and also to see the effect of imposing an external stress on the•peelaen* The salt contamination was effected by dipping the

•psoiaens in a solution of 1# NaOl, then drying in air to give asalt ooatlng of 16 ag/ca . Such chloride «ont agination enhancedthe oxldat ion rates at 600°0 In flowing oxygen by about 50jf overthat of uneoated speoiaens. Both stressing by tJ-bsnt and also bytmlaHal tensile testing (at a stress level of 20 Kg/an ) hare notresulted In risible crocking at a temperature of 35O°C for a periodof 72 hours.

4*1.4 Corrosion of oarbon steel in high teaparature water*Effect of dissolved oxygen sad EOTA additions.(S. Chakravarty and H.S. Qadlyar)

It was earlier reported that the growth rate of carbonsteel in lithlated water of pH 10*5 at 310*0 can be considerablyreduced by reducing the dissolved oxygen to leas than 0.1 ppa* Thestudy has been extended for lonair perlodsand also in water of | 1 7*0*On T»—>!««1"e the surfaoe both by x-ray and SEMt aagnetlte, (Pe-0,).was found to be the main constItuexs of the oxide. At pH 7.0, sninitially high percentage of fe20, (15 to 20jt after six days) wasfound. This has alaost ooapletely oonrerted to the protectiveaagnetlte after about 20 days of exposure. The 3M examination has

shown two layer DIMU growth, a thin, finely crystal l ine randomly

oriented base film, and over than uniform well defined much largercrys ta l l i t e s both consisting of magnetite. 3lhe adherence andprotectivaness of t h i s magnetite coating was found t o improve by theaddition of 300 pprs of sodium salt of 3DTA. This has resulted in

very low corrosion product release rate (0.72 mdd after 22 days).

Further studies •.v.Lth regard to composition and adherence of t h i s

coating with additiou agents on longer exposure are being continued.

b) Electrochemical rneasuremonts.

The electrochemical measuremeri s on plain carbon steeland on carbon s tee l with a inagnetite layer were carried out in 1M

HOH. The potential-tiaie curves indicated the attainment of as table passivity for both the cases in deoxyger.ated water. In anotherexperiment, the plain carbon s tee l was cathodically treated to obtainthe film free surface, and on obtaining a complete anodic polari-zation curve, two negative loops were dist inct ly seen, Indicatingthe solubility of the in i t ia l lower oxide films, before the build upof a passive layer. This passive layer has been identified to be?e_0 of thickness about 40A° from Ellipsometric measurements.

4*1.5 Ellipsometrio study of surface films on metals.(S. Chakravarthy and H.S. Sadiyar)

The ellipsometer, model L-119 from M/e Gaertner ScientificCorporation, haB been commissicned to init iate studies on thecharacterisation of thin surface f i las on metals. A beam of polarisedlight on reflection from a surface causes a change in the relativephase of the 'P' and (s* components and a change In the ratio of theiramplitudes. Measurements of these differences accurately with theellipsometer leads to the determination of n, the refractive indexand K, the absorption coefficient of the material. The instrumenthas been aligned and Initial measurements during standardisationusing a standard glass plate has given a value of n * 1.480, whilethe absolute value i s 1.516. A carbon steel specimen showed n • 2*381with air-formed oxide film, n • 2.594 with an oxide formed in 1 M

59

ZiOH for 24 hour* ana n - 2.991 after cathodio reduction of thelatter oxide film. The reported values of n for pure iron are between2.90 and 3.30.

An In-situ cell Is being designed at present to study theanodlo oxide films on Zr and on steel In 1 M LlOH.

4.2 STRESS CORROSION CRACKING

4*2.1 Microstructural e f f e c t s on SOC of slrooniun base a l l o y s .(G.C. Pa l i t and K. Elayaperumal)

Present inves t igat ion i s Intended t o reveal the structures e n s i t i v e SOC s u s c e p t i b i l i t y of various zirconium base a l l oys i naethanol • 0,4% BC1 so lu t ion . The a l l o y s studied were Zr»i£ Cr,Zr->2£ I e . Zr-2# Cu and Zircaloy - 2 . Al l these a l l o y s ar t suscept iblet o intergranular s t r e s s corrosion oraeklng i n alpha annealed o o n l l t l o n .8pherodlMtion treataent f i . e . prolonged annealing i n theet-phaserange, Induces aore s u s c e p t i b i l i t y t o SCC i n these a l loys* t h e a l l o y sare highly susceptible t o transgrsnular SCO in t h e p-quenohed a a r t e n s l t l ofora , further tempering iaproves SCO res i s tance : tempering for 24hours at 700°C ensures ooaplete ioaunity t o SOC i n Zr-0f Cr a l l o y ,due t o continuous net work of i n t e r a e t a l l i o ooapound at prior p - grainboundaries. S i a i l a r tempering trsataent In Zr-2^ Cr a lso iaduoeslaounlty t o SCC. but at eh net work I s not obserred. even af ter ageingfor a long t l a s (eohours) at 700°C. Isapsrlag for 8 hours at 700*Cshow optlans res i s tance t o SCC in Zr-1$ Or a l l o y , but not ooapletsIISJIIIHJ leapsred • a r t e n s i t l o structure has no s ignif icant e f fec ton SCC res is tance of Zr-2£ Fe andZlroaloy - 2 .

Annealing In the 4 + £ phase regions insures ooapli teto SCO in Zr • 2j( Cr alloy, attributed to the presence of

duplex euteotoid struoturs at the grain-bouDdarles. Similar treat-ment has no beneflolal effect on Zr - 1 Or. Such treataen* showspearlitio laaellar structure at the equiaxed «C grain boundaries la2r - 2jf f» without any iaproveaent in BCC reelstanoe. Ir - & Oudoes not show say susceptibility.

60

furnace cooled from the P -phase region al l the binaryalloys show Widmanstattan structure due to precipitation of platelets «surrounded by pearlitie eutectold. Stress corrosion crack is observedto propogate along4-plate duplex eutoctoid boundary in Zr-1$ Cr aniZr-2# Fe. Further work is in progress to correlate SCO susceptibilitywith respect to rode of oraek propogation, micrestructure and alloycomposition.

4*2.2 Iodine SCC of Zircaloy - 2.(K. Elayaperuraal, P.K. De and S.K. Ghosal)

The earlier work carried out with stressed zircaloy ringsexposed to iodine vapour at 300°C has not resulted in SCC. A newexperimental assembly has been fabricated for testing zircaloy fueltubes for SCC by pressure burst technique in the presence of iodine*

RAP? - type Zircaloy - 2 fuel tubes were tested in the as-received condition with graphite coating in the inside surface andalso with pre-hydriding in pure hydrogen. Stress corrosion testingwas done at temperatures of 300 to 400°C with applied hoop stressvarying from 27 to 33 Kg/on under the above condition. Iodineconcentration was varied from 1 mg/ca to 10 mg/om .

Testing at 400°C with 10 mg/em2 of iodine has resulted infailure in a very short time, as low as 7 minutes, whereas testing atsame temperature with 1 mg/om of iodine resulted in a failuretime of 10 hrs. Results of the further tests with 1 mg/cm ofiodine indieate that the time to failure decreases from 190 hours to10 hours as the temperature of test Increases from 300 to 400°C.lor cracking to occur the applied hoop stress should be around theyield stress of the tube (y.s. at 300°C - 30.8 mg/mm2). Graphitecoated tuba did not fai l for 240 hrs. at 400*0 whereas the asreoeived tube failed In 10 hours under similar condition. In theabsence of iodine small sjiounts of Hg (40 ppm) has no effect on the800 susceptibility.

61

SEM examination ahowed considerable corrosion product at the

Inside surface of the tube. No cracking was observed in the absence

of iodine .

4*2.3 Stress corrosion cracking of Heat Bxcbanger tube materials

i n high temperature water

(P.K. De and S.K. Ghosal)

Stress corrosion cracking of common heat exchanger materials ,

AISI 304. and 3041< s t a i n l e s s s t e e l s , Inconel 600, Incoloy-800 and

Mone1-400, has been studied in h i# i temperature water at 315°0 and

1500 p s i . The t e s t i n g has been done with U-bond specimens. load

was added t o water as Impurity since ASMS Boiler and Pressure Vessel

code cautions against the presence of lead compounds at temperatures

above 204°C. Lead was varied from zero t o 300 ppm, while oxygen

ranged. from<5O ppb t o 8 ppm. The room temperature pH of the water

was controlled at 9 . 6 . The exposure period was 1600 hours maximum.

The materials were t e s t ed in various metallurgical conditions: mi l l

annealed, cold worked and cold worked plus stress re l e lved . Results

indicate that type 304L s ta in less s t e e l , Incoloy-800 and Monel-400,

irrespect ive of t h e previous heat treatments, are res i s tant to

cradcing. Ineonel-iSOO, whether i t was mi l l annealed, cold worked or

s tress r e l e i v e d , f a i l e d by s tress corrosion in a l l t e s ted condit ions.

Severe cracking was observed in cold worked (25$) type 304 s t a i n l e s s

s t e e l specimens.in1'environmenta irrespect ive of the presence of Fb and

Shallow cracks were found in some m i l l annealed 304 s ta in le s s s t e e l

specimens. Cold worked plus s tress re le ived specimens of 304 s t a i n l e s s

s t e e l did not f a i l i n «tny of the environments.

lllcroscopicexsmination of the fa i l ed Incone1-600 specimens

ahowed a mixed intergranular and transgranular mode of cracking,

whereas 304 s ta in l e s s s t e e l showed transgranular cracking.

4 .3 CORROSION IN SAID? WATER AND HAIIDE SOLUTIONS.

4*3*1 Corrosion of Titanium, Cu-Ni and Ni base a l loys in flowing

sea water.(?.R. Shibad).

62

The Cu-Ni a l l o y s , In 838 and In848 and pure titanium were

exposed to Bea water at CIRUS Jetty at a flow v e l o c i t y of 2.4

meters/sec for a t o t a l period of 340 days. I t i s observed that

a l loy In848 i s better corrosion res is tant than al loy In838 (the mg/dm

values for In848 and In838 are 630 and 1415 r e s p e c t i v e l y ) .

Titanium i s found t o be unaffected in the above condit ions .

4*3.2 Galvanic corrosion of carbon s t e e l in sa l t water

(K. Elayaperwnal, S .S . Cbouthai and P.R. Shibad)

Galvanic corrosion experiments mild s t e e l has been studied

using aluminium brass as cathode in fresh tap water and synthetic

sea water, s t irred at SO r.p.m. for 1 day using a mixed cathodic

inhibitor of ZnSO , TK^p + HSOjNHg + NaHgPO at 6 and 60 ppm

concentration.

It was observed that even though corrosion rate increases

with reduction in area of mild steel (ratio of mild at eel to Al

brass varied from 1.06 upto 0.01) In both tap water and in

synthetic sea water,the inhibitor effeciency is 99$ for al l the

area ratios studied in tap water. In synthetic sea water also the

inhibitor effeciency increases with reduction in mild steel area.

However, 60 ppm inhibitor concentration shows better results than

6ppm. The efficiency i s however less than that observed in the

case of tap water.

4.4. CORROSION STUDIES IN VARIOUS ENVIRONMENTS

Corrosion of Hastelloy-X i n acids

(PJ l . Shibad)

In connention with a request from a f e r t i l i s e r industry

for evaluation of corrosion rat es of materials of construction f o r

phosphoric acid manufacture, the following programme has been carried

out . I t c o n s i s t s of t e s t i n g passive materials l ike Nickel, Kbnel,

Inconel and some Hastel loys in the f i l t r a t e of rook phosphate treated

with HgSO and a lso in straight acids l ike HCL, HNO? and H_PO .

Preliminary t e s t s indicated Hastelloy-X to be bet ter than the rest of

the materials . Detailed further invest igat ions were carried out with

Hastelloy-X. The t e s t s were carried out at different concentrations

The tes ta wera carried out at different concentrations and temperatures.

The effects of metallurgical conditions of the alloy on intergranulm-

corrosion in etan'lard Strauss solutions were also Btudied.

I t was observed that the corrosion rates are generally low

and wj£hin the acceptable value of 5 to 50 mpy (0.125 to 1.25 mm/yr).

The ra tes in concentrated 1IG1 and in other acids at elevated temper-

atures are olose to the higher limit of acceptance. I t was also

observed that th i s alloy does not get sensitized even after long-heat

treatment at the normal sensitizing temperatures of 600 - 900°C.

These treatments have not resulted in high corrosion r a t e s .

4.4.2 Corrosion studies of aluminium base alloys in HC1 with and

without organic inhibitors

(P.R. Shibad and K.N. Adhe)

Experiments were carried out on Al - 0.7$ Be and Al - 0.2$

miseh metal alloys in 1N HOT with varying concentration of acridine

(upto 1 gm/litre) as inhibitor. A simple model of adsorption i s

found to be satisfied by making use of the relat ion log 8/1-9 versus

log C, where • = surface coverage, C = concentration of the inhibitor

In molality. The resu l t s obtained are in reasonable nggrement with the

Langmuir adsorption isotherm. For the two alloys the inhibitor

effeciencies are well over 78/S in 1N HC1.

4«4.3 Corrosion behaviour of wrought and electrodeposited nickel

in alkaline environments - effect of NH , S~, and Cl".

(K. Elayaperumal, P.X. De and S.K. Ghosal)

Corrosion behaviour of wrought Ni and electro-deposited Ki

(ED-Hi) in KOH solutions at 25°C with or without contaminants l ike

NH,, H_S and Cl" has been studied by potentiostatic anodic polari-

zatic iT current decay behaviour at controlled potentials and by weight

loss techniques. Results showed that corrosion ra te of both wrought

64

Si and ED-Ni in 6M KOH solution was negl ig ible . Passive current

density for ED-Ni wosof the order of 10 arap/cm , 100 to 200 times

higher than that of wrought Ni. With the additions of NH , H S and Cl"

in 6M KOII solutions, the corrcB ion ra te of ED-Ni was greatly enhanced

and was in the range of 40 t o 100 mdd. Corrosion ra te of wrought N^

was marginally increased to 0.23 mdd in only Cl~-eontaining KOH

solution while no appreciable weight loss was observed in 6M KOH

solution containing e i ther Nil or II S. In these solutions the

corrosion potent ial for both wrought Ni and ED-Ni became more ac t ive .

Passive current was unaffected by addition of NH, or Cl~ t but increased-3 2

t o 10 amp/cm by the addition of HgS. The lower corrosion resistance

of ED-Ni, par t icular ly in the presence of contaminants, i s explained

in terms of sulphur pick up during pla t ing.

4 . 5 . ELECTROPLATING 0? ALLOYS AND COMFOGIDES

4.0.1 Electro deposition on Nickel - Manganese alloys

(A.K. Grover and John T. John)

Continuing the programme on the electro deposition of a l loys ,

studies have been made t o electrodeposit wear and oxidation res i s t an t

nickel manganese alloys from metal chlorides contained in dimethyl

sulphoxide-water mixture bath. The effect of various parameters l ike

pH, temperature and current density (C.I>) on the composition and

quali ty of deposits was studied from 60 raole/S Mn-20 Mole$ Ni bath.

Studies have shewn tha t smooth, br ight , th in coatings of n ickel -

manganese alloys containing 10 to 90 wt/o Mn can be deposited from

80 mole$ bath by adjusting the plat ing parameters.

Not much change in deposit composition was observed with

change in bath composition from 30 mole'/o Mn to 60 mole# Mn. Studies

conducted from 30 and 60 mole/S Mn bath t o establish the role of

ammonium chloride addition showed that i t does not affect t o any

appreciable extent the composition of the deposit . However, i t -

improves the bath conductivity and 1.0 t o 1.5 M NH^Cl i s necessary

to get good quality deposits. In general, increase of C.D and

decrease in bath temperature decrease the manganese content of the

alloy for a l l the baths studied. Current effeciency of alloy deposition

showed a slight upward trend with increase in bath temperature.

The optimum bath conditions to obtain a smooth, adherent and

shining alloy deposits from DMSO - water mixture bath are as follows:-

20-80 mole# Mn, Hi + Hh 1-1.5 M., ammonium chloride 1H, 5\% DM30,

50 gpl glycine, pH » 3 , 50°C temperature and cathode current density

of 4-40 A/dm2.

4.5.2 Photo fabrication of porous nickel tubes(A.K. Grover and John T. John)

Studies were carried out to standardise the conditions toeleotreform porous niokel tubes using photofabrication technique.Aluminium wasused as expendable mandrel. After cleaning and dryingthe mandrel, i t was coated with a photoresist and exposed toultraviolet radiation through a negative transparency having thedesired pattern. Exposure and development process was standardisedto get a good quality pattern on the aluminium surface. Plating wasdon* from nickel sulphamate bath, S-Nickel shots were used as anode.In the present study, patterns of 330, 540 and 1060 microns were used*A series of eleetroforming experiments were conducted for varying timedepending upon current density and the starting pore size of pattern.It was possible to electroform good quality porous niokel tubes 4-5 mil*7*8.5 mil and 7 n i l thick using 330, 540 and 1060 microns patternrespectively. As the thickneae of electroform was increased, the holesstarted olosing. The maximum thickness of tube i s limited due totapering overgrowth of metal within holes.

In order to achieve greater tube thicknesses, the plating was

carried out in two stages. Resist ooated mandrel was exposed for 15

66

minutes as thicker resist coating was applied. After getting the

proper pattern on the mandrel, i t was plated 13.5 A/dm2 to give 1.5-2 mil

thick nickel deposit. Aluminium mandrel was then dissolved in alkali ,

followed by acid treatment of the niokel mesh. Porous niotel tube i s

further plated at the same current density. It was possible to

olectroform thicker porous nickel tubee. Porous nickel tubes of 7-8 mil,

9*5-10 mil and 20 mil thickness oould be electroformed using this tvro

stage technique with 330, 540 and 1060 micron patterns respectively.

The nickel electroformed from tbie bath has microhardnees 280,

tensile strength 64 Kg/mm and 5.4'jo elongation. Tensile strength of

nickel decreased to 18.5 Kg/mm and elongation increased to 37.1$ on

annealing in vacuum at 750°C for 90 minutes.

4*5*3 Electroplating of refractory metals(Sohan Singh, A.K. Grover and A.L. Pappachan)

Work on fused salt electroplating of various refractory metd. sof interest like ziraonium, tantalum e t c . , which cannot be electroplatedfrom aqueous bath, was taken up. Studies were initiated to electroplatecoherent deposit of zirconium from fused salt bath using zircaloy-2 scrapas anode. The bath consists of 16.3wt.$Kj,ZrFg in a ternary eqtectic ofLiF-KF-NaF. Purified argon gas passed through the system during electrolysis.12 mm and 16 mm dia copper £ rods were usecl as cathodes. A few experimentswere conduoted at 75O°C-8OO°C, at cathode current density of 2A/dm for3-4 hours. In the preliminary experiments either non uniform metalliccoating or only a flash coating was obtained. Qualitative spectroscopicanalysis of the metallic coatings confirmed the presence of Zirconium metal.

4.5.4 Elect rode posit ion of Ni/iliO composites

(if.IT. Joshi and II. Totlanl)

Ni-NiO eomposites have potential applications in M.H.D. Programmes.

Studies have been initiated to co-deposit NiO with niokel. NiO in the

bath has been varied from 25 gpl to 125 gpl. The deposition has been

carried out at 35 A/dm for four hours, the temperature and pH being

55-58®C and 4 respectively.

67

It was possible to obtain smooth electroplates of Hl/ttiO

composites oontaining a maximum of 5$ NiO from a bath containing

125 gpl of NiO. The ductility of deposits decreases with the amount

of NiO in the deposit. After heat treatment at 35O°C for 1 hour In

vacuum, the plates showed considerable ductility*

4.6 ELECTROPHORETIC DEPOSITION

4*6.1 Electrophoretie deposit ion of n i c k e l oxide( K. Elayaperumal, M. Totlani and A. Ramasamy )

The work on electrophoret ic deposit ion of green n i cke l oxidehas been continued with n-butanol and tr ichloroethylene mixture asthe suspension medium. Parameters a f fec t ing the deposi t ion rate atroom temper* ure such as concentrat ion of n i c k e l oxide i n the suspension,composition of the suspension medium, applied voltage and deposit iontime have been studied i n d e t a i l .

It was observed that with the increase i n n ioke l oxide concentrationin t h e bath upto 75 fipl. the rate of deposit ion increases and beyond t h i sconcentration i t remains pract ica l ly constant . Deposition would not beachieved from e i ther cure n-butanol or pure tr ichloroethylene bath. Aminimum of around 15 v o l . # tr ichloroethylene was e s s e n t i a l t o get auniform depos i t . With further increase of tr ich loroethy lene , the ra teof depos i t ion passes through a maximum and deposit ion ceases af ter aconcentration of about 55 v o l $ . Rate of deposi t ion Increases l inear lywith applied voltage and time of deposi t ion i n the range 100-4007 and15-240 seconds r e s p e c t i v e l y .

4.7 ELECTRCWINNIN& 0? RARE-EARTH METALS

4 . 7 . 1 Blectrowinning of Lanthanum(Sohan Singh and A.L. Pappachan)

Work on preparation of pure lanthanum from lanthanum chloride

i n HaCl-XCl bath was carried out . In an e l e c t r o l y t i c c e l l having 40 wt./C

68

LaCl in NaCl-KCl an charge, experiments were conducted at 96O-97O°C

with molybdenum cathode and graphite container as anode. For short

duration, a current effeciency as high as 95$ wa3 achieved. The

current effeoioncy was found to be highest at a cathode current density

of 7.5 Amp/cm . The maximum yield was 88$ when the amount of ampere-

hour passed was 50$ more than the theoretical amount required for

complete deposition of lanthanum. It was observed that current

effeciency fa l l s down, rapidly, when the concentration of LaCl, in the

melt cones down to lesei than 20 wt#.

4.7.2 Preparation of Oobalt-Cerium alloy

(Sohan Singh and A.L. Fappachan)

The work on getting cobalt-cerium alloy ,f or making permanent

magnets was continued. The alloy was prepared by various methods

mentioned in the earlier report. It was found on analysis that there

i s a loss of cerium during the induction melting. To get the right

composition (CeCOj.) of the alloy, 2$ excess cerium was taken over

the stochiometric amount. The alloy was crushed to a fine powder

and the average diameter of the particle was found to be 6.9 f- by

Fisher Sub Sieve Sizer method. The coercivity was found to be over

300 Oe in an applied field of 4 KOe. Further work i s in progress to

improve the magnetic properties of the alloy.

4.8 EIECTRCW INNING OP METALS USING PARTICULATE BED CATHODES

4 .8 .1 Eleetrowinning of Ni from d i l u t e NiSO^ so lu t ion

(M. Tot lani and P.R. Singh)

The study of electrowinning of Ni from d i l u t e NiSO s o l u t i o n

on t o a part icu late bed of Ni has been continued. Effects of various

parameters l i k e temperature, e l e c t r o l y t e flow rat e , concentration

of Ni i n the e l e c t x o l y t e c e l l , current and pH of the feed on the

cathode current effeciency for Ni deposi t ion were s tudied.

Effecienoy was found t o increase with temperature, Ni

concentration and pH of feed so lut ion appreciably. It var ies l i n e a r l y

with Ni concentration in the feed between 1 t o 3.5 g p l . Effect of pH

of feed was very marked. At pH 1.35 i t was l e s s than 10$ while at

pH 5.0 i t was around W.($. The effeciency increased with c e l l

ourrent i n i t i a l l y and then saturated at around 600 ma. The effect of

increase in bed height from 1.1 cm t o 1.8 cm was not appreciable.

4 .8 .2 Packed bed electrodes

( M. Totlani and P.R. Singh )

Study on packed bed graphite electrodes has been taken up t o

treat very d i lu te so lu t ions . The system studied i s CuSO -H SO .

The preliminary c e l l was made of 1.2 cm bed of graphite part ic les

(+20, -7 mesh) ln«"3>1 cm ( i . d . ) g la s s tube. A nicke l mesh was used

to feed current. Anode was under gravity maintaining aconstant column

over the sintered g la s s d i s c , fused to support the bed. Two concentrations

of Cu, i . e . 5X1O~3M and 1X1O"3M in 1M H 2S 0

4 were used. It has bean

found that the l imit ing current for Cu deposition increases with

copper concentration in the e lec tro ly te and the e l ec tro ly te flow.

4 .9 INTEK SECTIONAI/DIVISIOHAL PROGRAMMES

4.9*1 Collapse and ridging behaviour of RAPP fue l pins

(P.K. De)

A programme has been undertaken in collaboration with PPED,

RED and RMS t o study the effect of y i e l d strength and pe l le t -c lad gap

on the collapsing and ridging behaviour of RAPP fue l p ins . Half

length f u e l pins of RAPP type, with y i e l d strength varying from 49000 poi

t o 58000 ps i and' the pal let clad gap varying from 0.003" t o 0.008" were

tes ted i n autoclaves at temperatures ranging from 315fa t o 500°C and

pressure from 800 ps i t o 1500 p s i . The ridges and oval i ty formation

were measured by a profilometer. With t e s t ing at 315°C, 1500 ps i for

20 hours, the largest oval i ty changes about 100*»have been observed

i n elements which had the largest diametral gap, irrespect ive of the

y ie ld strength.

70

Circumferential ridges of maximum 60ftwere obtained in thetemperature range of 400°C to 500°C and 1500 psi. The formation ofridges seems to be independent of the cladding yield strength ordiametral clearance In the element in the temperature range of 350to 500°C. The circumferential ridge formation appeared to bestrongly dependent on the temperature beyond 35O°G. Based on theseexperiments, recommendations were made regarding the pallet-clad gapand yield strength of the clad.

4.9.2 Hot conditioning of the P.H.T. system of RAP? IX(N.S.D. Klayathu)

The section has actively collaborated with the PREWAC groupin the hot-conditioning of the primary heat transport (JHT) system ofRAPP II . The main objective of hot conditioning i s to obtain auniform and adherent coating of magnetite which wi l l serve as aprotective layer for the carbon steel pipe lines of the system. Thisprotective layer, besides minimising corrosion of the structuralmaterial acts as a check on the crud inventory thus controlling activitytransport during operation of _Jhe reactor. The hot conditioning wasconducted for 20 days during April 1977 at a temperature of about200°C and a pressure of 80-86 Kg/cm with recirculating demineralisedwater of pH 10.5 (adjusted by the addition of requisite amount ofLiOH) and controlled low level of osygen (less than 10 ppb) usingcalculated additions of hydrazine. Coupons of the various structuralmaterials comprising the PUT system, v iz . carbon steel , 304 S.S;403 S.S; Monel-400 and Zirealoys (2 and 4) were introduced in theautoclaves installed for the purpose in a bypass to the main PHTsystem. The results have shown that the build up of magnetite coatingon the carbon steel surfaces i s fast in the in i t ia l stages, slowlyreaching a plateau of thickness of 17 rag/dm , equivalent to 4*5 microns,at tha end of hot conditioning. The adherent nature of magnetitecoating was reflected In the very low crud values in the system water*X-ray analysis has established the Integrity of the magnetite coatingat the end of hot conditioning.

The rest of the structural materials were found to be notannntniahlv.

71

4.9.3 Corrosion studies in desalination systems at DSED(P.R. Sbibad and K.N. Adhe)

The committee for corrosion studies in desalinationsystem is set up by DEED, Metallurgy Division and Atomic FuelsDivision. The desalination group faci l i ty at DEED i s beingexploited for studying the corrosion behaviour of metals of interestunder various conditions of desalination. The group has fac i l i t i e sfor installing tubular samples in which the treated sea water flowsinside* The tube are heated by steam froa outside. Preliminarytrials have been carried out so far.

4.9.4 Corrosion testing of monel tubes in alkaline solutions(H.S. Gadiyar)

In response to a request from Atomic ?uels Division,two monel tubes with longitudinal scratches on the surface werecorrosion tested in 50% NaOH at 3OO°C (saturation pressure) in orderto check the acceptibility of these tubes with scratches for boilerapplication. A 15 day test has shewn corrosion rate of 0.17 mils/year*There was no preferential corrosion on scratches or any cracking.

4*9.5 Plating of t i n on niobium.(A.K. ftrover)

Niobium-tin (lib, Sn) compound is a useful super-conductingmaterial. To help develop the necessary technique for preparingthis compound for Physical Metallurgy Section, t in plating on niobiumwas done from acid t in fluoborate bath. 20 to 30 micron thick t incoating was obtained at room temperature. The t in plate was given aflesh coating of apper from alkaline copper tartar ate bath followedby thickness build up from acid copper sulphate bath*

4*9*6 Study of Antimony deposition(M. Totlani and S.K. Athavale)

In response to a request froa Electronios Division, study of

12

electroplating of aatlmony from fluoride bath was taken up. The

bath contained antimony oxide dissolved in 40$ HP. Tetrahydrofuron

was added to this solution. Smooth deposite were obtained at

a current density of 25 jn.a/cm . Pew elect]

have been supplied to Electronics Division.

2a current density of 25 jn.a/cm . Few electrodeposits of antimony

4.9.7 Chromium plating of copper foi ls for Mossbauer studies(A.K. Grover and John T. John)

In response to a request from Isotope Division, anumber of copper fo i l s were chromium plated to a thidcness of 15 to30 microns for preparation of sources for Uossbauer studies. Thecopper fo i l s were supplied by the Isotope Division. Few samplesof ehBomium plated fo i l s have been supplied to them.

—acoOox—

73

5 . CERAMICS

Ihe Ceramics Section is engaged in the Research and Development

programmes on (1) Nuclear Ceramic materials as E0 2, UO_-ZrO2 and BeO,

(2) Special high temperature oxide ceramics for MUD application as A1.0-,

MgP, and rare-earth oxide stabilized ZrO., (3) refractory ceramics as

mullite, zirconia, zircon and beryllia, (4) electrical ceramic materials

as barium titanate, Hi-Zn-Ferrites, high alumina and beryllia components

and high alumina substrates, (5) ceramic solid electrolytes as calcia

stabilised zirconia and ihOg-YgO, and (6) fabrication of calcium fluoride

crucibles, oxide refractory ware and insulator components against

specific requirements.

5.1. HUCLEAR CERAMICS

5.1.1. Development of UOg plate-type fuels

(S.V.K. Rao, B.D. Zope, N.S. Anandan and P.V. George)

For the Plutonium Recycle Project, the development work for the

fabrication of thin sintered UOp platelets for making plate-type fuel

elements was continued.

5.1.2. Sintering Studies on ZrO2-UO2

(P. Das)

Solutionising and sintering studies were continued on mixtures of

UOg-ZrOg containing 5 to 25 wt# UOg at calcination temperatures ranging

from 1000°C to 1503°C, and sintering temperatures ranging from 1500" to

1560 °C. It is observed that in general, as the solutionising temperature

is increased, the sinterability becomes poorer, and the maximum

sinterability has been exhibited by powders solutionised at 1200°C. For

the powders solutionised at temperatures upto 1200°C, it is observed

that the sintered density is high increasing with increasing amount of

U0 2 content and temperature of sintering. On the other hand, for powders

solutionised at temperatures beyond 1200°C, the sintered density decreases

as the U0 2 content is increased; also, the extent of densification

decreases with increase in solutionising temperature for any given

composition. Further studies are in progress.

X-ray studies indicated no unreacted UOg in powders solutionised

74

above 1200'C. The amount of tetragonal phase.formed and retained was

higher with increasing temperature and additions following the phase

diagram. For example, a volume percentage increase of the tetragonal

phase from 8.29$ to 66,O5# was observed with 25$ additions for powders

solutionised at 1300°C to 1560°C as against 5.25# to 7.35# for 10$

additions*

Based on the results some sintering trials i at 1800°C were taken

in argon atmosphere. A very high densification for the raw materials

mixed as such was observed but the high temperature tetragonal

modification could not be retained completely in these samples. Powders

solutionised at 1300eC and 1500°C, however, had shown a single phase

structure (tetragonal) depending on amount of addition. For powders

solutionised at 1500°C, 20 & 2yA additions had shown a completely single

phase (tetragonal) in powder diffraction pattern. But for addition less

than 2056, the specimens were found to be a mixture of monoclinic and

tetragonal.

5*1*3. Studies on BeO.

(R. Bhat)

Investigations were carried out to study the influence of

additives and calcination temperature on the powder properties and

sintering behaviour of BeO derived from beryllium hydroxide.

The influence of three sintering aids viz. 1wt?SMgO, TiOg and

FegO, on the properties of BeO powders derived by calcination of the

coprecipitated hydroxide at 900 °, 1000* and 1100°C were studied. The

different powder properties studied were surface area by BET method,

crystallite size by x-ray line broadening and particle morphology by

electron microscopy. The sintering behaviour of these ponders was

studied in vacuum, and the distribution of the addition by scanning

electron microscopy.

The crystallite sizes calculated from three reflections (100),

(002) and (102) were found to vary} the amount of variation depending

on the addition. The powders calcined at 900*C with additions had

larger crystallite size (245 A for pure and 350 A with additive). With

75

increase in calcination temperature to 1100 °C, the crystallite aize of

the powder with MgO increased to 800 A*, whereas those with the rest of

the additions increased to 5^0 A. Pure BeO and BeO with MgO had ap

surface area of '}Q and 54 m /gm respectively at 900 °C which decreased2

steeply to 5«1 & 3.5 m /gm at 1100°C. In case of the powders with TiO

and Feo0_ the fall in surface area was gradual, decreasing from 47 and2 2

38 m /gm to 14.5 and 14.5 m /gm respectively.

The ratio of particle size to crystallite size showed large

increase with increase in temperature from 900° to 1100°C for pure powder

and for the powder with MgO (increased from 1.4 and 1.1 at 900°C to

11.5 and 7.5 at 1100cC), The ratio increased only by a factor of 2 for

the other two powders. This shows that at lower calcination temperatures,

the particles consist essentially of individual crystallites. At higher

calcination temperatures, the particles grow at a faster rate than the

crystallites and this growth is more in case of pure BeO and in BeO with

MgO, Such particle growth is retarded in case of BeO with TiO. and Fe-O,.

Higher fydration tendency of the former two powders is believed to be

a major factor influencing particle growth,

A common feature observed in electron microscopic study of the above

powders was the presence of spherical and needle type particles along with

irregular shaped particles. The majority of the fine particles were

spherical especially at lower calcination temperatures. Particles with

straight edges and rounded corners, plate like particles and few sintered

aggregates were present in higher temperature calcined powders. The

amount of needlen present was more in pure BeO and in BeO with TiO^ and

scarce in the other two powders.

In case of 900°C calcined powders when sintered in vacuum, the samples

with MgO and TiOg attained a density of 2.7 gm/cc at 1200°C and those with

Pe-O, attained 2,86 gm/cc, With increase in calcination temperature to 1000"C,

the sintered density improved to 2.84 gm/cc at 1200°C for the samples with

TiOg and F«2°3 but 3reduced *° 2»29 gm/cc with MgO, Higher calcination

temperature of 1100*C reduced the sintered density of the samples,

•specially affecting the powder with MgO which attained only 1.92 gm/cc

at 1200*C. At 1400*C, the three samples with MgO, TiOg and F e ^ attained

densities of 2,73, 2.9 and 2.9 gm/cc respectively. All the above additives

are found to be good sintering aids when oaloined at optimum calcination

temperature, The deleterious effect at higher calcination temperature

especially with MgO as additive is attributed to growth of large partiole

and crystallites and drop in surface area.

Study of the polished and etched sintered pellets with the

additives by scanning electron microscope showed a uniform distribution

of the additive when the amount added is small. A higher quantity of

addition of the additives was found to result in their seggretfition at

grain boundaries or inside the grains restricting the grain growth in

case of MgO and TiCL additions* However, In case of Fe-O, addition the

grain size is enhanced and it is attributed to the formation of liquid

FeO in,.,the grain boundaries.

5.2 SPECIAL CERAMICS FOR MHD APPLICATIONS

(S.V.K. Rao, S.K. Roy, CM. Pathak, G.T. Kamath)

the Ceramics Section has taken up the assignment of developing

insulating materials and ceramic-electrode materials for the high

temperature MHD channels for power generation.

5.2.1 Development of Sintered MgO

For the development of sintered MgO of optimum microstructure for

MHD channel lining, a study on the alkali seed attack on magnesia was

taken up on MgO bodies developed. The alkali is introduced into the

plasma to increase its electrical conductivity at the operating

temperature. And the successful performance of the refractories in

the MHD duct depends much on the ability of material to withstand

erosion by high velocity gases and corrosion by the alkali seed.

The static corrosion of magnesia by KgCO, was studied. The extent

of alkali attack on magnesia was evaluated by following the alkali

absorption and dimensional changes of the impregnated specimens after

thermal treatments, at 1^00°C to 1500°C v/ith a soaking of two hours at

each of these "temperatures, Microstructural changes were noted using

the organic replica method.

. The material formed out of an equivolume mixture of aotive and

fused magnesia by sintering at 15OO°C to a density of 855* T.D. underwent

77

degradation and failure at 1500°C. The weakening of the intergranular

bond was evident even at 1400°C. In some of the pellets, extensive

fissuring occurred. In the preliminary investigation, it was observed

that incorporation of TiO to the extent 5# by wt to fused magnesia

aided in sintering (bulk density at 1500°C was 93# theoretical) as well

as enhanced its capacity to withstand alkali attack, This aspect will

be studied in detail.

5.9.2. Studies on Activated Sintering of Magnesia.

The studies on the activation of the sintering process in fused

magnesia were pursued in the following categories, viz., (1) Addition

of various ammonium salts NH F» NH.C1, HH.NO, - in amounts upto 10$ by

wt, (2) Addition of decomposable salts of magnesium, viz. MgCO_, Mg(0H)_,

Mg(CH,CO2)2 - to 1he extent of 10, 25 and 50#. (3) Adsorption of

inorganic acids like HP, HC1, HNO_, HgSO and H»PO on the particle

surfaces of magnesia.

In all these cases, 1he bulk density value on sintering reached

To bring about /the bulk activation in fused magnesia, minor additions

of various atomic species were tried. The selection of the additives

was guided by ionic size, compatibility, ability to form defect structure

and ability to form liquid phase. The following oxides were added t

Nb2O5, V2O5, MoOj, Pe2O5, MnO2, SiO2, C r ^ , SeO2, TeO2, TiOg, NiO,

BgO,, Cr2O_, CoO, CUgO, GeOg, BigO , SbgO-, WO^ and Ta20 . In the

preliminary studies, TiOg, Ga20,, Nb2°5» V2°5* Fe2°3 and NiO were found

to promote densification in fused magnesia to 85$. TiOg addition

helped sintering of fused MgO to more than 93$ at 1500°C.

j.3. HEPRACTOBY MATERIALS

5 o.1. Studies on Stabilization of Zirconia

(P.Y. Dalvi)

During the period efforts were made to increase the densification

of stabilized zirconia. The influence of thermal cycling oh sinterinft

behaviour of partially stabilized zirconia was studied.

78

Compacts of uncalcined mixture of zirconia containing 0«5« 2,0 &

5#1 "HrfcjS CaO were subjected to thermal cycling in two temperature ranges *

l) lower range between 7OO-12OO°C and higher range between 7OO-14OO°C.

Though on 1st cycle, the sintered density decreased compared to

that of those normally sintered at 1200°C or 1400°C with 2 hrs soaking,

a steady increase in density occured as the number o£ cycles progressed.^

There was optimum density from 11 to 25 cycles (i?«6 gm/cc). It was

observed that the densification obtained after 25 cycles in case of

higher temperature range cycling with 0.5% addition of CaO was equivalent

to that obtainable by normal sintering at 1600°C 2 hrs.

The results indicate that thermal cycling promotes densification

in case of partially stabilized material compared to fulHy stabilised. Zr0o,

This seems to be due to number of rapid phase transformations in partially

stabilized ZrOp.

5.3.2 Development of Zircon Refractories.

(A.K. Kulkarni and P.Y. Dalvi)

Thermal shock resistance tests were carried out on briquatte samples

made from two selected compositions using sintered zircon grog from earliez*

work* These briquettes werejprepared from grog of gradr:. .^ain sizes, and

sintered at 155O°-160O°C/2 hrs. Sintered density of (the rrog was within

the xange 3.73 and 3.77 gm/cc. The test samples were sintered at 140O°C/2hrr.

and had attained density of 2O7 - 2.8 gm/cc and o&en porosity around 36 to

38& These samples showed no cracks upto 20 cycles from 1400°C to room

temperature after which the test was discontinued. There was no change in

'ilensification after the test, while those sintered at 155O°C/2 hrs and

subjected tc thle test stood the thermal shock upto 20 cycles but some

lowering in :V2nsity was observed after the test was over. Ability to

withstand such severe thermal shocks indicates that these samples will have

good thermal shock resistance.

5.3*3. Studies on Mullitisation

(B.R. Vyas)

Studies were continued on the factors that influence mullitisation

of actllite bodies* Microstructural studies on mullite bodies sintered at

79

1G00°C for one hour were carried out using the scanning electron

microscope. The following observations were made from ihe

fractographs studied:

(i) 'ihe mullite bodies, without the incorporation of minor

additions did not snow any significant formation of mullite needles*

(ii) 1 wt# of minor additions of FegO,, Mr#2 or ZnD caused the

formation of smaller mullite needles compared to 3 wt?& additions.

(iii) The prominent interlocked raullite needles were observed

in case of 3 wt# addition of equal parts of Fe20_,.and MnD2; also In case

of 0,2 wtfo MgO and 2.5 wt# FeJ),» Further microstructural work is

under progress.

X-ray analysis was also carried out to compare the mullite

content, in the various sintered mullite bodies as listed earlier,

using x-ray diffractometer and Cu K'•< radiation. X-ray difflactometer

charts were taken on all the samples using Geiger Muller counter at a

constant rate meter adjustment and the peaks were recorded between 15°

to 70° of Bragg angles in 2 0, The comparison of peak height for

Mullite content was carried out for the strongest Bragg reflection

obtained at 2 0=26.06° corresponding to d=3.42 •£. The results of the

data are as follows.

1) Clay as such sintered at 1400° for 2 hours gives a peak

which corresponds to formation of mullite,

2) at 16OO°C, the peak height ranges between (60-93$) in

all the compositions of Mullite bodies.

3) 1 wt# and 3 wt# of additions of equal parts of Fe20_ and

MnOg or MgO and FegO, enhance the peak height (72-87$

compared to 1wtj6 and 3 wt# additions of Fe2°3» MnOg or

ZnO (57-75^).

4) Without any minor addition of mineralisers, non-calcined

clay and alumina mixtures of mullite bodies give maximum

peak height (93$.

Further work is in progress to study the effect of minor

additions on Mullite bodies synthetically prepared from the mixture

of Al20, and Si0? of chemically pure grade*

80

5.4 ELECTBICAL CERAMIC MATERIALS

5,4*1 Development of High-Alumina Components for BEL

BEL imports a large variety of high alumina components for

their use. Out of these, two components of 92$ alumina re required

in quantities much larger than the rest* BEL requested for developing

these two components in the first instance* In addition to the

complexity of their shapes, they should meet the following specifications

on electrical properties.

Dielectric constant 8*5

(1 Mhz)

Dissipation factor 0.0006

(1 MHz)

Volume resistivity at 10 ohm-cms

300 °C.

This development work wa3 taken up and 92$ and 95$ alumina

bodies which sinter to imperviousness at 1400°C have been developed*

When the first set of specimens of 92$ alumina were fabricated

and sent to BEL for evaluation, it was reported that though the

specimens were completely impervious, their volume resistivity was low

being 10 ohm-cia at room temperature and the dissipation factor quite high

being 0.028?, Bused on the above results, the alumina powders were

given certain leaching treatments and specimens from these were found

to show a significant improvement in their electrical properties.

This work was carried out further with certain modifications

and the latest set of iiapervious specimens prepared and sent were

evaluated and it is reported that their electrical properties are vexy

satisfactory and are :Ln the acceptable range. The values attained are

given below:

Dielectric constant 9*66

Dissipation Faotor O.OOO34

(at 1 MHz)

Electrical Resistivity 8.2x10 ohm-cm

(at room temperature)

81

A larger number of specimens are being prepared now to

establish the reprouuoildlity of the electrical properties.

Simultaneously, the fabrication of the two dies to make the

two components has been taken up with the central workshop, and trial

pressings will be started on receiving the dies.

5..4.2 Development of Sintered BeO Components for BEL

(R. Bhat)

Sintered BeO discs and rings of various diameters from 5 mm to

13'mm are required for electronic application as heat sinks and

washers. The requirements of such she.pes are high density and zero

open porosity. Preliminary studies on the fabrication of such discs

were carried out with various imported BeO powders and those derivfcd

from sulphate obtained by processing one of the imported powders. Since

it is difficult to sinter pure BeO to high density in air, efforts were

made towards developing a suitable additive for promoting densification.

Among the number of additives tried, CaO and MgO appeared effective in

aiding densification. Based on these trials, numerous sintered specimens

of BeO were fabricated and sent to BEL and their electrical properties

have been evaluated. In some of the specimens, 1 wt?£ of minor additions

of MgO, CaO or Fe2O, had been incorporated to improve sinterability.

Some of the specimens were also made from a more active BeO powder

prepared by disaolving the as-received material and crystallising out as

sulphate, calcining back to BeO, and then incorporating the above

additions. It is observed that the dissipation factor values of all ihe

above samples ranged from O.OOO67 to 0,025 as againat the specified value

of 0,0002, Olie resistivity values ranged from 1.73 x 10 to 1.21 x 10 *

as against a stipulated value of 10 ohm-cm. It is considered that a

further purification of the starting BeO material, is necessary. One

experimental lot of purified BeO has been prepared by the Beryllium

Project, Sintered specimens are being made with this, for evaluation of

the sintering behaviour and electrical properties.

p ,4.3 Development of High Alumina Substrates.

(A.K. Kullcarni and D.D. Upadhyaya)

Studies on the development of high alumina substrates were

82

continued. During the period, techniques for, minimising warpage in

thin alumina substrates were established, and further,trials for

obtaining desired as-fired surface finish as well as grain size were

made through various sintering treatments. In continuation of studies

for use of antishrinkage agents, the use of pyrophyllite was studied in

detail. Pyrophyllite an alumino silicate mineral, being soft and having

less shrinkage and having chemical composition similar to clay was found

to be a good replacement for clay, the other minor additions remaining

the same as in the originally standardized high alumina body. Overall

shrinkage decreased to B°/a with slightly lesser density i.e., 3.4. instead

of 3.6 - 3.7 em/cc. However, the composition became impervious at 1400°C

with a longer soaking period of 8 hrs. The dielectric properties, were

found to be identical with the earlier clay alumina bodies (K = 8-9 &

D<.002 at 1 MHz)

Though by Jising pyrophyllite in place of clay and by controlling

the rate of rise of temperature the warpage was reduced, to meet the

specifications on flatness, use of lapping and polishing operations

became necessary. However, in these operations it was observed that

the surface gets contaminated with unwanted impurities and gets torn.

Hence, attempts were made to obtain the required surface characteristics

by controlling the surface microstructure. Desired surface finish in the

as-fired state was) attempted by a sintering treatment where a sintering

was done at a hi#ier temperature (15OO°C) to develop"\the grain size to

2-3 u. . With further soaking exaggerated and non uniform grain growth

takes place. So to stabilize the structure and grain size already

obtained, further soak was given at a lower temperature (1400 OC/7 hra).

Biis technique was found to be very .useful to obtain uniform grain size

and even grain growth.

The trials showed that with a specific sintering treatment

(150072 hrs + 1400o/7 hrs) desired as-fired surface finish having grain

size 2-3yu and CIA between 30-50 u-inch could be obtained with

combination of raw materials like alumina and pyrophyllite with minor

additions like MgCO, & TiO_. Samples have been submitted for further

evaluation to the Electronics Division.

5.4.4 Development of High-Permittivity BaTiO, Capacitor bodies.(BaaPrMod)

(1) High Permittivity Barium Titanate C apacitors*

Barium titanate bodies with 0.1 wt% and 1 wt# additions ofand CeO2 were prepared. These oxides were added

to barium titanyl oxalate powder, which was calcined at 800 °C for4 hrs. Samples were sintered at 1250 s, 1300° and 1400°C for 2 hrsin air* The effect of other sintering atmospheres like vacuum,nitrogen and hydrogen was alto studied. Samples sintered in hydrogenatmosphere were sintered in air at temperatures of 800"C, 1000° and1200% for 2 hrs. Some samples were given an extended soaking of16 hrs also. The physical and dielectric properties of sinteredsamples were determined*

It was observed that the sintering treatment and the natureand concentration of the additives have a pronounced influence on thedielectric properties of barium titanate. In pure BaTiO, powders orwith higher concentration of additives, high dielectric constants(~» 40,000-50,000) were obtained by first reducing the material inhydrogen and then- reoxidising in air at ~» 1000°C. In comparison tothis, for powders with small concentration of additives, highdielectric constants (—>100,000) could be obtained in a singlesintering treatment in air. Sintering in nitrogen or vacuum yieldedeven higher K values. These were of the order of 177,000 (LagO, Ng)170,000 CeO2,(vacuum), 158,000 ( N b ^ , Ng) and 101,000 ( T a ^ , » 2 ) .Higher sintering temperature, longer soaking period or a higher concentrationof additives resulted in much lower values of dielectric constant.Hence, it was possible to obtain barium titanate ceramics with veryhigh dielectric constant and reasonably low dissipation factor by asuitable choice of the additives, the sintering temperature and thefurnace atmosphere.

5.4.5 Development of Hi-Zn-Perrites

(Bam Prasad)

Magnetic Fluidsi

Development of suitable magentic fluid for application in high-

84

vacuum magnetic seals, as required by Nuclear Physics Division was

continued. Efforts were made to form stable suspensions of Ni-Zn-Ferrite

powders in high-vacuum oil. The powders were obtained by three different

routes, viz. calcination of co-precipitated oxalates, direct precipitation

of f errite in highly alkaline medium and solid state reaction of the

component oxides. Formation of a stable suspension was facilitated by

grinding in an agate planetary mill and using oleic acid as dispersing

agent. Amongst the various concentrations of oleic acid used, a 10 vol?6 of

oleic acid in vacuuir oil was the most successful. It wa3 observed as a

result of extensive laboratory trials that ferrite powders, obtained from

oxalate route or solid state reaction, when suupended in vacuum oil containing

10 vol# oleic acid, yielded stable suspensions after 150 hrs of milling.

Further work is in progress,

5..5 DEVELOPMENT OF CERAMIC SOLID ELECTROLYTES

(S. Ramanaiban and S.K. Roy)

The development of YDT (Yttria doped thoria) electrolytes was

pursued. Compacts of YDT material prepared by the Sol Gel method in

the form of spheres having a diameter of 400 microns were sintered in

flowing Hg atmosphere. The sintering "behaviour was found to be very

poor.

To produce sinterable YDT powder, calcination of coprecipitated

oxalates of Th and Y and also of mixed nitrates was carried out.

The calcination was carried out at 9O0°C/<2rrs« in air. The samples

were isostatically pressed at 20,000 psi and sintered at 15OO°C/5 hrs.

The oxalate-derived samples sintered to about 6&/0 T.D. The nitrate-

calcined powder yielded samples with 76$ density.

The solid solution formation during calcination was followed

by X-ray diffraction method. While the nitrates yielded solid-solution

of Y in ThO. readily on calcination, the oxalate resulted in mixed

oxidea only. Sintering of YDT samples at higher temperatures to

attain better density is being attempted.

85

5.6 DEVELOPMENT OP CERMETS

(P.K. Agnihotri)

Development of various Composites/Cermets received much

attention in the search of high temperature materials for various

applications requiring adequate strength and hardness which in turn

depend on the particle size of the dispersed hard phase in a given

composition.

Composites are d*fined as two or more dissimilar materials

intimately bonded to form an integral structure to attain improved

properties. Structural cezmets are particulate composites of Metal/

Cermics, Bonding of heterogenous phases takes place by mass

transport in solid state, whereas in liquid phase sintering action

of chemical potential gradients and surface tension forces are

important.

An assignment hasbeen taken up to develop Nickel Alumina

composites. In this work, major effort was made to develop partioulate

composites of Ni/Al-O- by Nickel coating of Alumina particles through

mechanical alloying* For this purpose a mixture of fine alumina

powder 0.06 micron size and freeze-dried Nickel powder of 500 R

particle size was used. Metal coated alumina powder particles were

obtainedby mlcronising the powder mixtures. The Nickel contents

chosen in these cexmets were 10$ 20% and 30% by wt.

Cold pressed samples from these coated powders were sintered

at 1200*0 and 1^00°C respectively for one hour. Specimens sintered

at 1200*C were found to be porous having poor strength. However,

samples sintered at 1500 °C had good denaification of the order of

89% theoretical aid good strength. Further densifi cation of the

order of 95% theoretical could be obtained by prolonged soaking for

8-10 hrs at 1500*0,

5,7 STUDIES ON SIHT3RING MECHANISM

5.,7,1 Studies on Oxide Powders

(G. Eswara Prasad)

It has been established that the origin and the thermal

history of oxide powders have a major influence on their crystallinity

which in turn affects their sintering behaviour. It is hence felt

that the material movement during sintering depends strongly on the

degree of crystallinity of an oxide powder. A study was made to

examine the behaviour of powders having different degrees of

erystallinity and to assess crystallinity quantitatively.

In-oitu eleotron beam heating studies in the transmission

electron microscope on different materials (amorphous and crystalline)

were conducted with a view to following the sintering process. These

Studies showed significant morphological changes in the powders during

sintering. Subsequently, some selected samples were studied in the

hot stage of the electron microscope at temperatures upto 1040°C, usiry*

* constant low beam current to observe the difference in the sinter:? n^

behaviour of different powders. An attempt was also made to study tte

thermal decomposition - induced evolution of magnesia from magnesitua

hydroxide. For these studies, a technique was developed in which a thin

film of magnesium hydroxide was prepared on nickel grid. Hot stage

Microscopy was carried out on this film to follow the development oi

erystallinity in the magnesia powders derived from three parent

compounds - hydroxide, carbonate and oxalate - at various calcination

temperatures ranging between 400* - 1200°C and Warren and Averbach'n

method was used to evaluate strain and effective domain size* The

percentage degree of crystallinity was calculated using crystallinity

index method of Wakslin, Virgin and Crystal. Microstruotural changes

that took place in sintered magnesia pellets were studied under the

teaming eleotron microscope. Ihese pellets were prepared from

magnesia obtained from magnesium hydroxide and the magnesium oxalats

en oaleination at 800*0 and also from fused magnesia and the

tsmpsistmes used for sintering ranged from 900)*0 to 1400°C in air for

two hoars under identioal conditions*

The following conclusions oould be arrived at on the basis of

the observations mads in the above work;

1) Oxide powders derived from different parent compounds

by oaleination do not have residual miorostrain* as

revealed by x-ray line profile analysis.

87

2) The degree of crystallinity is a more important panuMter

than the crystallite size in relation to the ainterability

of an oxide powder.

3) The origin of an oxide powder has a significant influence

on the process occuring during calcination, hence on the

degree of crystallinity, the crystallite size and the particle

size of the powder.

4) Sinterability and tnlcrostructural development can be

correlated with the rates of change of the degree of

crystallinity, the crystallite size and the particle size

with temperature.

5) Nuoleatlon and grain growth can be noticed only after the

degree of crystallinity attains a certain minimum value,

generally over 75%.

6) When a powder is poorly crystalline, the mechanism of

densification is akin to that in an amorphous powder like

glass.

The sinterability and the progress of densification depend on the rate

of change of crystallinity, particle size, crystallite size and

the development of mlcrostructure,

3*7.2 Studies on Sintering Diagrams,

(Aahok Mohan and N.C. Soni)

The mechanisms by which material movement takes place during

sintering are not only interesting but also very important in

determining the properties of the end product and suitable sintering

schedules etc. In spite of substantial efforts invested in this

field, the agreement on issuesis only limited. The classical exponent

method, initially proposed by Kuchrnski, has resolved the issue to

an extent and has been the mainstay of this field. However, it has

handicaps which could not be by-passed. Ashby has recently broken

away from the classical approach and has suggested a method of

constructing what he calls the sintering diagrams. The area defined

38

by axes representing nonnalised. neck size (x/a) and homologous

temperatures (T/T_,) is divided into fields in which a mechanism is

predominant. This is determined with the help of suitable rate

equations representing the mechanism. The other variables that he

has contented with are particle size (a) and initial pore volume

fraction (f). This method resolves major problems in the exponent

method like ambiguity in criterion and a simultaneous consideration

of a large number of mechanisms and sintering variables becomes

possible.

Although Ashby's method has great potentialities, the exercise

gets increasingly complicated as the number of mechanisms and/or

variables are increased. To overcome this, a computer programme has

been designed in this effort. In addition, a new method of

constructing sintering diagrams is suggested. The computer output

is in the form of Relative Contribution Diagrams (RCD), EachT

situation defined by x/a and =• is represented by a space in whichm

a group of 25 digits are printed. The number of times that a digit is

repeated gives the contribution of the mechanism that it represents.

The additional advantages gained by this new method of

construction are (a) The extent of predominance is revealed (b) It is

possible to predict circumstances under which ihe contribution of a

mechanism would change (c) The speed with which a mechanism gives way

to another with change in one parameter is clearly seen. This could

be very useful in establishing sintering schedules.

Work is being extended with the help of RCD and a rationalised

basis has been suggested for determining x/a at which the stages of

sintering change. The diagrams are also being used to study sintering

mechanisms in UOg. This study is revealing important sintering variables

and properties of the material that influence the relative contribution

of mechanisms.

5 .8 ADVANCED HIGH TEMPERATURE AND MATERIALS DEVELOPMENT PROGRAMME

(Co-ordinator: Ashok Mohan)

A need for a facility to generate high temperatures has been

realised. Especially for development of materials capable of

89

surviving severe conditions that are, at times, encountered in

nuclear and space industries. A group has been formed to look into

the alternatives for high temperature generation. A preliminary

report is to be prepared £<• identifying potential methods of

generation, direction in which the initial research efforts need to be

made and to broadly determine the nature and quantum of inputs required.

The first leg of the programme consists of developing systems

like plasma heating and ion bombardment, which are parts of ongoing

programmes. Second leg consists of extending the present systems

to higher levels of temperatures. The initial efforts regarding the

latter have been started by way of modifying the existing design of

Molybdenum resistance furnace to obtain substantially higher

temperatures than the present level of about 1800oC, Possibilities of

using lasers to advantage in high temperature generation and material*

research have also been investigated.

5.9 STATUS REPORT OM FUSION TECHNOLOGY

(Ashok Mohan)

A report on the status of Fusion Technology has been prepared.

For this, the alternative approaches of current interest both in

magnetic and inertia! confinement, have been studied. A perspective

on the plans in the light of the targets and magnitude of investments

had been developed. The problems being faced were identified as also

the gap between available and required technology. Information on

related subjects like environmental impact of fusion devices,

authoritative opinions on current status, materials requirements in

fusion systems etc. has also been appended to the report that has been

prepared.

5.10 CERAMICS FABRICATIONS

(S.V.K. tfao ard B.D. Zope)

In the Ceramic fabrication facilities of the Section, from tine

to time various items of ceramic products were fabricated and supplied

to diverse users under DAB, Some of such items supplied are give

below,

(1) Alumina shapes 5.6 + 0.05 mm in diameter with

four holes for NPD (225 Nos.)

90

(2) Ihermal shock resistant alumina body from fusedgrains of alumina suitable for the fabricationof HFC trays.

(3) Ceramic nozzles for sand blasting

(4) Button shaped' ceramic pieces •3000cI?o8. and asuitable raw glaze' for the above pieces for theIsotope Division

(5) Alumina rods 3 mm dla and 250 mm length for theflame spraying gun for BED.

(6) Crystal seed holders for TPD

(7) CaP2 crucibles for Radio Chemistry Division

91

LIST OF PAPERS PUBLKilBD/ACCEPTED/COMMONICtfBD FORPDBLKJATION/PRESENTEa) DURING THE YBAH 1977

1. Gas distributors In f lu idiod beds:D. Sathlyarooorty ft Ch. Sridhra RaoAccepted for publication in Powder Technology, U.K.

2 . Bubbles at the Gas Distributor* in Fluldled BedsD. Sathiyomoorty ft Ch. Si<l'ara RaoPresented at the 7th National Conference on Fluid Mechanic*and Fluid Power (Nor. 1977)

3 . Multi o r i f i c e Plate Distributor* in Ga* Fluidiaer Bed* -A Model for the Design of Gas Distributor*.D. Sathiyamoorthy ft Ch. Sridhsra RaoCommunicated for publication In Powder Technology

4* Studies on Eleetror©fining of Caloiothermic HafniumI.G. Sharma and C.K. GuptaJ . of Huclear Materials, 74(1978) 19-26.

5 . Pi lot-plant Production of Niobium.C. Narayanan, T.K. Mukherjee, O.K. Bo** ft C.K. Gupta.Trans. I .I .M. 30 (Dec. 1977) 387-9*

6 . An Evaluation of Vanadium Oxyoarbide a* Ladle Addition ofMolten S tee l sD.K. Bose ft C.K. GuptaMet. Trans B, 8B (Dee. 1977) 601

7. Pyro and Hydro-metallurgy of nickel and MolybdenumExtraction from the ir Sulphide*A.K. Suri , T.K. Mukherjee, B.K. Boae ft O.K. GuptaPresented at the International Conference on Metal Science -The Emerging FrontiersVaranasi Nor. 23-24, 1977

8 . The Development of * flow-*he*t for prooesalns IndianViokel-Copper Sulphide Concentrates.P.P. Shukla, T.K. Ilukherje* and O.K. Gupta, Met. Divis ionR.A. Nagle, K.S. Koppikar ft T.K.S. Murthy, Chemical Xngg. D i m .Aocepted for Publication In Trma. In*t . of Mining ft Met. (See 0 ) .

9 . riectrometallurgical research at the at tract ive MetallurgySection, Bhabha Atomic Research Centre.T.IC. Mukherjee ft O.K. Gupta.Surface Technology, Vol.7, Wo.5 (1978) 347-352

10. A Chloridlslng Boasting routs t o Reoorer Nickel from aSulphide ConcentrateP.P. Shukla, T.K. Mukherjee, C.K. GuptaPresented at the 31st Annual Teoh. Meeting of X.I.X. heldat I . I .T . Madras, 14-16 HOT. 1977

11. Production of Chromium by Molten Salt ElectrolysisA.K. Suri ft O.K. GuptaSurface Technology 5 (1977) 271-276

12* Studies on the fabrication of aluminium bondedboron carbide ringsA.K. Suri & C.K. GuptaAccepted for publication In J. of Nuclear Materials

13* Development of graphite lubricated fuel for heayy waterpower reactors.T.K. Mukherjee & C.K. GuptaTechnical Report, BARC

14* On the aluminothermic reduction of calcium vanadate.O.K. Mehra & C.K. GuptaMet. Trans B, SB (Dec. 1977) 683

13* Some aspects of pilot plant production of Micronsize Zirconium Powder by Calciothermic Reduction ofZirconium Oxide.S. Chaudhary & T.S. KrishnanTrans. IBl 30-4 (1977)224

16. Decomposition of Zircon by Soda Ash Sintering Proceee.P.R. Morion, J.1I. June j a & T.S. KrlehnanAccepted for publication in Trans. Inat. of Miningand Metallurgy^ U.K.

17. Application of free energy - composition diagrams inpredicting the sequences of phase transformations InZirconium - Niobium al loys .E.S.K. Menon, S. Banerjeo ft R. KrishnanTo be published in Metallurgical Transactions

18. Kinetics of alpha precipitation in Tl-6 *t% Cr andTi - 11 vt% Mo.M. Unnikrishnan, E.S.K. Menon ft S. Bonerjeet o be published In Journal of Materials Science.

19* Non-equilibrium precipitation in Zr-5 la*E.S.K. Menon ft P. HukhopadhyayTo be published in International Journal of Metallography*

20* Discontinuous precipitation In a MartenslteP. Mukhopadhyay ft V. RamanTo be published la International Journal of Metallography

21 . formation off a ! » „ phase in Zlrooniua-Aluminlua aartensites.P. Mukhopadhyay, 7. Raman, S. Banerjee ft R. KrlabnanTo be published in Journal of Material* Science

22*- The effect of heat treatment rariablee on the atruetureof commercial Ti-OAl-fflo-rv alloy3.J. rijeyajcarj S. Banerjee ft R. KrishnanTo be published in Trane. IM.

23* Applications ok transmission electron aloroeoopgr la pbaaetranefomet ion*S. Banerjee ,. 'Preeented at the DAB Materials SoienoeRotirkela, Octobert 1977.

24* Structure proprty correlation in the alloy Ti-8Al-1Mo-1TS.J. Vijayakar, S. Banerjee ft S. Erlahnanibid

2$. Phase transformation in Zirconium alloysR. KrishnanPresented at International Conference on Metal 8olenoeeTaranasllorember, 1977

26 Mionrduplex structure in the T1-6A1-4V alloys*S.J. Vijayakar, S, Banerjee ft R. Krishnanibid

27. Phase separation In the Ti-34 at^ lib alloy.E.S.K. Wenon, S. Banerjee ft R. Xrlshnanibid

28* Precipitation in dilute Zr-Sn alloysXhu Nalk ft S. Banerjeeibid

29* Influenoe of second phase dispersion on voidformation during IrradiationM. Sunderaraman* S. Banerjee A R. KrishnanPresented at the Xndo-German Seminar on Radiation Senate, Kalpa'HOT. 1977

30. Blistering by ion bombardmentO.K. Sood, M. Sundararaman ft R. KplshnmPresented at Surface Science Symposium, Bombayleb. 1977

94

31* Onherenoy etrain contrast arounrt Ni_Hb precipitatesV. Sundarafaman ft &. Banor.ieflPresented aS Tenth Annual Conference of Electron MiorosoopeSociety of India, BombayDecember 1977

32. Precipitation reactions in a EH 13-8M0 stainless e tee l7 . Seetharanan, M. Sundararaman 4 H. Xrishnanibid

33» Practographio inreet igations on Ti-15^ HoUna Naik, G.E. Praead & S. Banerjeeibid

34* Quenched and tempered structures in Zr-5TaB.S.K. Menon, P. Mukhopadhyay A S. Banerjeeibid

35. Variations in work hardening and dislocation structureswith difonnation temperature in Zirconium & TitaniusF. Bodrl^nez, P. Muldiopadhyay, S.S. Vagarali & H. KrishaanIbid

36* Strength and deformation behaviour of Ziroonium-TitaniumnarteneiteaS. Banarjee, S.J. Vijayalcar ft It. KrishnanOommunioated t o Act a Metallurglca

37* Inoompreeeibility of atoms in :intermetallio phases withI I - and DO „ structures1 a la t t i ce parameter approachB.s.K. Henoft ft P. lfukBopadhyayCommunicated to Materials Research Bulletin

38. Strain ageing in Zirconium - 2.5 wt/£ niobium alloyT.K. Stohaft M.K. AsundiJournal of Nuclear Materials, 67 (1977) 315

39* Effect of strain rate and temperature on tens i le propertiesof heat treated Zirconium - 2.5 wt£ niobium alloyT.K. Sinha ft M.K. AsundiJournal of tfuclear Materials, 67 (1977) 311

40. Deformation of the martensite In Zr-1,.5Sn and Zlroaloy»2tV. Haman ft P. MukhopadhyayTo be published in Journal of Materiala Solenoe

41 . Keohanioal equation of state In Ziroonlua alloy*T. Raaan ft P. KukhopadhyayTo be published la Physio* Status Solidl

95

42. Internal friction measurements In a V-2OT1 alloy containingOxygenS. Mishra ft S.S. VagaraliPresented at the DAE Materials Science Symposium) Hourkela,October, 1977

43* Strength of dilute zirconium-copper aartensiteeB.L. Wadefcar, V. Raman ft P. Mukhopadhyayibid

44* Mechanical equation of state la Zlrooalta alloy*V. Raman ft P. MukhopadhyayPresented at the International Oonferenoe on Xetal*Soiences, Varanaei, November, 1977

45* Internal friction techniques In the study of radiationinduoed damageS. MishraPresented at the Indo-German Seminar on RadiationDamage, KalpaWcam, November, 1977

46* Evaluation of materials for End- shields in OAHOT reaotorsV.7. Ramanibid

47* A new method for the evaluation of internal stress forstres8-ctra±n transientsV.V. Raman & M.K. AaundlComnunicsfced to Act a Metallurgi.oa

46* Keehanioal Behaviour of quenohed and neutron irradiatedZirconium, Ziroaloy-2 and Zr-1?» Al allojrU.K. Hatta, I .S. Batra ft B.D. SharaaIrans IM 30 (1977) 240

49* Point defect Behaviour ft phase stability problnsin alloysB.D. SharoaPresented at Indo-German SsBinsr on Sadist ion DsaafeT Xalpakkalov. 1977

90* Spontaneous vacancy condensation on Oas BubblesO.P. Tiwariibid

$1* Defect structure ft post irradiation Annealing inneutron irradiation Hiokel bass alleysI.S. Batra, M.K. totta ft B.D. ShsnaTrans. IIM 30 (1977) 92

96

52. X - Particle irradiation induced precipitation aidphase instability in concentrated Fe-Cr-Ni alloysB.D. Sharraa e t .a lTo be published in Radiation Effects Journal

53« Isochronal Annealing of Electrical Resistivity ofElectron irradiated concentrated Fe-Cr-Ri alloysB.D. Sharma et .a lTo be published in Phil. Mag.

54. Position Annihilation studio son Electron and X - particleirradiated 75 Ni-13Cr-12Fe alloyS. Mantl, B.D. Sharma & G. AnteabergerCommunicated to Phil. Hag.

$5. A correlation between vacancy formation energy and compressibilityR.V. Pati l & G.P. TiwariIndian J . Pure and Appl. Phya. 15-3 (1977) 206

56* Modification of Richards Rule and Correlation betweenentropy of Fusion and allotropic behaviourG.P. TiwariTo be published in Metal Science Journal

57* The correc t Ian between the entropy of Fusion and thediffusion behaviourG.P. Tiwari \To be published in Trans. Japan Institute of Metals

58. A phenomenological model for diffusion in solidsG.P. TiwariSubmitted for publication in Trans. JapanInstitute of Metals.

59. Chemical Diffusion studies in Titanium- Iron systemG.B. Kale, S.V. Khera & G.P. T1™">irlPresented at Annual Technical Meeting of ID1, Madras, HOT. 1977

60. Dissolution Kinetics of Zirconium HydrideM.D. Vora, K.5. Shivaramkrishnan & G.P. TiwariSubmitted for publication in Trans. IIM

61. Failure of Stainless steel line carrying He to CIRUSreactor vessel tube sheetR.C. Pant & H.S. GadiyarPresented at the Symposium on operating experience ofNuclear Reactors and Power Plants} Feb 7-9» 1977» BABC

97

62* Aluminium base kg alloys for DesalinationH.S. Gadlyar, H.S.D. Elayathu ft T.P. JoshiPresented at the Symposium on 'Protection ofMaterials in the Sea1 held on 25-26 Peb, 1977 at lavalChemical and Metallurgical Lab, Bombay

63* Corrosion of carbon s t e e l in high temperaturesdissolved oiygen and pH effectsS. Chakravarty ft H.S. GadlyarPresented at the 1st National Conf. on 'Corrosionand i t s Control1 RRLf Hyderabad, 26-28 June 1977

64* Bllipsometry in Surface Film AnalysisS. Chakravarty ft H.S. GadlyarPresented at the 7th DAS Materials Science Symposium,Rourkela, Oct. 1977.

65* Effect of impurity elements Al, Mn ft Hg on the corrosionresistance of Zircaloy-2 in high temperature water and st<H.S, Gadlyar - Presented at the International Conference onMetal Sciences « The Qnerging Frontiers Hov. 25-26, 19771 Varanasi

66. Corronion behaviour of wrought ft electrodeposited nickel inalkal:lne environments - Effect of ammonia, sulphide ft ChlorideP.K. ])e, S,K. Ghosal ft K. Elayaperumalibid

67* Corrouion Studies of Cu-9#Sn-4i£Al alloy for salt water servicePresented at the symposium on Protection of Materials in theSea held al; NCML Bombay during February 25-26, 1977P.R. Shibatt ft K. Elayaperumal

68. Corrosion jiroperties of nidcel free auotenitio s ta inlesss tee l as oompared t o 18/8 s tainless s t ee lP.R. Shiba lPresented v>t the 1st National Conference on "Corrosion andI t s Control" held at Hyderabad, June 26-28, 1977

69. A Recent Case study of Boiler Tube FailureK. Elayaperuoalibid

70. Structure Dependent Corrosion of Metal* ft AlloysK. Elayape»oanalPresented at the BAB Material* Science Symposium, Rourkela, Oct. 1977

98

71* Some Typical Corrosion Failures in Chemical and ProcessIndustries and their PreventionK. Elay&perumalChemical Concepts Feb, 1977

72. Blectroforming of Porous nickel tubesA.K. Grover & J.T. JohnPresented at the 31st Annjtal Tech. Meeting of Indian inst i tuteof MetaJa, Madras, Nov. 1977

73* Fine tungsten metal nowder by hydrogen reduction of W0_P.R» Singh, M. Totlanift J . Dalachmdr* *To be published in Trans. IBf

74* Corrosion Problems in Nuclear Power P in t*} Types, Analysesand Remedial MeasuresK. Elayaperuual & C.7. SundaramPresented at the DAE Symposium on Operating Experience ofNuclear Power Reactors & Power Stations, BffiC, Feb. 1977

75* Physleo-chemioi. Studies on Powders and their sinterabil itySintering of Uranium Dioxide PowdersN.C. Soni, Ph.D. Thesis (1977)

76. Studies on the Sintering of Beryllia - Influence of MinorAdditions on Sintering of Beryll ia PowdersB. Bhat, Ph.D. Thesis (1977)

77* Studies on the Mechanisms of Sintering - Sinterability of Oxide PowdersG. Eewara Prasad, Ph.D. Thesis, 1977

78. High Permittivity Barrier and Boundary Layer Capacitor*K. Thiagarajan, Earn Prasad & S.V.K. RaoPresented at the Symposium on "Surface Phenomena in MetallurgicalProcesses", held at IM, Bombay, 19-20 Feb, 1977

79. Ceramic Surfaces Belated to the Sintering ProcessesS.K. Roy, CM. Patha & S.V.K. Raoibid

80. Influence of Calcia Addition and Calcination Temperature onSintering and Stabilisation of ZireoniaP.Y. Dalvi 4 V.K. MoorthyPresented at the 41st Annual Technical Meeting of the IndianCeramic Society, Bangalore, 28-30 April 1977

8 1 . Influence of Minor Additions and Sintering Trwfc a n t s onthe Density and Microstruoture of Sintered Urmia Pel letsN.S. Anandan & V.K. Moorthyibid

* Improvement of Properties of Sintertable Uranium Dioxide PowdersN.C. Soni & V.K. MoorthyTrans. Ind. Cer. Soc. 36-2 (1977) 26

99

83 • Sintering Mechanism DiagramsAshok Mohan, N.C. Soni, V-K. Jain & V.K. UoorthyTo be published in Science of Sintering Journal.

84 . High Temperature Phase Diagram for Zr-Mo and Hf-Ho5 .P. Garg and R.J. Ackerm&naMet. Trans. 8A (1977), 239.

85. High Temperature Phase Diagram for Th-Mc, Th-Re, IMIo and U-Re|Derived Thermodynaraic Properties of Refractory Metal Solutes Inliquid U & ThS.P. Garg and R.J« AokermennJ. Nuel. J.later. 64 (1977), 265.

86. High Temperature Phase Diagram for Zr-0S.J. Ackermann, S.F. Gnrg and E.G. RauhJ. Am. Ceram. Soc. 60 (1977) 341.

87. Refining of Reactive MetalsC.V. Sundaram, S.F. Garg and J.C. SehraPresented at the International Conference on'Motal Sciences -The Emerging Frontier*, SHU, Vnranasi, 1977.

88. Beryllium Development Programme i n IndiaK.S. Subbarao, B.F. Sharma, C.11. Paul and G.v. sundaraaPresented at the International Conference on 'Berylliua*, 1977(Metals Society, London, October, 1977).

89. Special Metals Development - Assessments and ProjectionsC>K. Gupta and G.V. SundaramPresented in Conference on 'Recent Developments i n Non-ferrousMetal Technology1, Indian Institute of Science, Bangalore, 1977*

100

MECAUAJEGY COIiIOQUB? SERIES

The fo l lowing l i s t g i v e s the l e c t u r e s he ld under MetallurgyColloquim during the year 1977•

Sr.Ho. Date Speaker Topic

1 5.1.77

2 18.1.77

3 2.3.77

4- 17.3.77

5 23.3-77

6 15.4.77

7 7.5.77

8 31-5.77

9 19.7.77

10 25.8.77

11 6.10.77

Dr.B.V. Harasimha RaoUniversity ofCalifornia, Berkeley

Prof. Khuliaan WilsdorfUniv. of Virginia,Virginia

Dr. A.M. GolshaleIII Kanpur

Dr.M. Kageswara RaoKidhani, Hyderabad

Shri A.K. SuriMetallurgy Division

Dr.S. MishraMetallurgy Division

Shri Sohan SinghMet. Divn.

Dr.S. UisbudUniv. of NebraskaLincoln, USA

Shri Ch.Sridhar RaoMet. Divn.

Dr.G. VenkataramanERC

Shri K.S.Subba RaoMet. Divn.

Phase Transformations andDesign of Alloys

Bardeen-Herring ClimbVersus Vacancy Precipita-tion at Dislocations

Quantitative Metallography

Fatigue Crack Propagation inPrecipitation HardeningAluminium Alloys

Electrometallurgical Methodsof molybdenum production

Anelasticity in Zr,Ti andtheir alloys

Hare earth Metals extractiontechnology

Subliquidus Immiscibility asan Essential Precursor tocrystallization of s i l i ca-alumina metals

Structure and BehaviourFluidised beds

Stochastic approach toAnelastic creep

Powder Metallurgy ofBeryllium

101

13

14

15

16

17

18

Pate

10.11.77

16.11.77

17.11.77

18.11.77

21.11.77

1.12.77

3.12.77

Speaker

Dr.K.H. WeetmacottLawrence BerkeleyLab., USA

Prof.H.I. AaransonMichigan Technoloi?gioal Univ., USA.

Prof. NewmannMax Planck Institutat Dusseldorf

Tpplo

The effect of interstitialImpurities in Secondary DefeatFormation in Quenched Metals

Solid-solid Nuoleation Theory tExtensions, Testing ftApplications.

Bracture Mechanisvs

Prof. M.C. Flemings Recent advances In solidi-MIT, USA

Dr.W. SchillingKPA, Jullch

Dr.G. OatbergAB Atomenergie,Sweden

Prof.J. levyEcole dee Mines,Paris

fication technology

Self Interstitial* la Metal*

Safety and Reliability ofNuclear Pressure Vessels andAncillariea

High temperature phasetransformations in stainlesssteels.

*brtractive Metallurgy Section

Dr. C.K. Gupts,SO(SP)(Bead of eeetlon)

Retractive Metallurgy SectionMetallurgy

1HFC

Project*i

Hewof SpecialMaterialsPlar.t.

Tit Mi usPilotPlant7.5 t/y

Bessarch 4 Developmenton Refractory Metal*

Process Development & BadeBessarch '

HEr

*AK Surl (SD)OK Kehra (sc)C Harayanan (SB)KIT Hair SA(c)

IProject planning for3.C production andfabrication, Prepa-ration of boron,boral. Metallo-thermy of oxides,halldes & sulphidesof refractory metals(ffl>fTa,V,Kofw) andcarbothermy of (Kb &Xa) for metal,ferro-alloy and superalloy preparation.

Hdcberjee (ss) IS Krishnan(SB)

JC Sebra (SB) SP Garg (SB)

BB Mahendra (SD)Sudhir Handa (c)PP Shukla (SC)P?3 Pillai SX(C)

Admn.£ Supporting Staff7

IDerelopmentarelating tographite coatedfuel and plasmtechnology.Extraction ofMo and VS. fromtheir respec-t ire sulphideintermediatesand electro-extraction ofrefractory• • ta le .

Sort.IS PL Yijay (SD) B Verikata-ThoKa«(sc)lG Sharma(SD) .. raaeni (SD)

IB Menon A Uhnl- JM Juneja(SD)SA(c) krishnan Si(c) B Kriahna-

PK Raja- moorthy (c)gopalan SA(c) TJ Ehatt (sc)B? langri SA(B)

I I IDevelopment Reclamation of Thermodynamicand fabrica- Zr 4 Ti from studies oftion of R(co), scraps. alloy systems(R.S.) alloys Studies on and oxide-for perma- magnesiotber— carbide re-nent magnets, ndc redtetion actions*Development of rutile,HfO_ . IMP measure-of TIC for Purification ments of solidheating and of crude metal electrolyteroutine spec- by molten salt system,trocbemical electrorefln- Developmentanalysis of & iodide of solidrefractory process. Pabrl- electrolyticmetal3. cation of Hf galvanic cell

shapes. technique for

TitaniumTechnology

Ch« SrldharBao (SB)

D Sathiya-moortby (c)

C Subra-aanian (SC)

nathan Si(c)

IBasic andApplied(Boast-ing,Oxldationtpyro-carboncoating),Studies onfluldlsation.Fused saltelectrolysisof M.C1..Oxidatidn ofindustrialFeCljSOlution.

Beryllium Project Section

CM Paul, SB

IB.P.P. Project

KS Subbarao DBP Shftrnw, SDJS Hair SC

ISetting up of the Beryllium H l o t Plantat Vashi, New Bombay : Design of plant,equipment and machinery; Co-ordinationof c iv i l , electrical and ventilationworks; Procurement, testing and erectionand commissioning of equipment andmachinery*

Beryllium Project SectionMetallurgy Division

IDevelopment Programmes

SA Kulkami7D ShahMG BajadhyakshaHH HakhasiaK Maramdu

CSCSC

SA(CSA(C

IStudies on the preparation ofberyllium metal, starting withIndian beryl and Cu-Be alloys- Fabrication of Be metal andCu-3e alloys - ultra purifica-tion of rare metals*

O

Supporting Staff

XD Salunke I'man (c)

Metallurgy

Physical Metallurgy Sactian

Dr.K.r. JUranii, SO(SF)(BaaA af Seotian)

5

Hetal Jhyaics Grauf

Dr.Dr.Dr.UCSEGB77B7IS1(1?EC

B.D.Shaxisa.G.P.TiwuriP.K.K.Ifeyar

SaxemKheraKaleOfcgiPati lBatraVijayaknaarPaliwal

(SP)(SE)I SB)(S3)(SD(so(SC(SC(SCI(sc)SAfl

SS t r u c t u r a l S tud ie s Graup

Dr.R. KrlshnanCNBaaDr.S. BauerjeeP MukhapadhyaySJ TijayakarIa l i t EuaarSat.. Una NiikESS MenanTO KulkarniU Sundararaaana ITnnikrishnanMD Y*r?ID Baburaj

Mechanical Praper t l ee Graup

P Dasgupta*TK SiuhaHN TankS Mishra7N Sathe7 Vericitaraaan7 BaaanJK GhakravartbyNT PareHiAB TanhanoSI> VadekarR Kishure

Tracer diffusion studies 1.in aeta ls and allaysIrradiati*n effects »naeshanical properties *f 2 .rtetals a.nl a l loys , studiesan nucleatiau and spowth ofvoids and bubbles, 3 ,Precipitatian and diffu-3ion controlled reactioni s Zr-bsse a l loys .

Adan. & SUpparting StaffStenographer 1Fareaan 1Draughtsitan 1 1Traiesaaa S 1Tradesman ? 1Tradesman E 2TnAesiaa 0 2

:«aan B T

Thin fila transaissien sl«o-fcran nicrasc»py »f 2c and Ti-baa« allaysC«rrelati#i3 »f .-aechanical pro-perties with alectx»n aiore-structure in Ti-oAl-47Study »f hydride prscipitstianin zircaniuni and its a.XX»ys

Tecbnioal Services

Rl{ Arya (SE)Supeivisian af Divisianal ??«c!c-shap, fabrication and aaixite-nance af aquipaerrt.

Ad in. 2c Supparting Staff (cantd..)Helper B 1

*0n deputation aaraad at

1. Stre^fchsning aechanisas inzircaniua all«ys

2. Ei«raally activated deftxaatianstudies

3. Internal frictian studies due tasalutes i s HCP aetals

4. He I ting and fabrication af allaysparticularly af allays af nuclearindustrial iapartacce.

Corrosion and Electrometallurgy SectionI

Dr. K. Elayaperumal, S.O.(SF)

(Head of Section)i

Corrosion

iMaterials for Reactor

Applications

Dr BS GadiyarS3 ChouthaiBC DeSV IhadnisGC PalitSK GfaosalKB Gaonkar

Studies on zirconiumalloys, aluminiumalloys, carbon steelsand stainless s teels .

iMaterials for Desali-

nation Systems

NSD ElayathuHI ShibadKN Adhe (SA-«B')

Studies on Al-base,Cu base and Ti-basealloys.

Basic studies on corrosionConsultancy service and Assistance

Suoportin&Staff •Trad*smm ( B ) 1Tradeacan ( C ) 1Stenographer ( J r ) 1

Electrometallurgy

5Hydronetallurgy and

Elect rcro-inn-lng

« TotlaniSohan SinghSB. SinghAL PappachanSir Athavale13H Joshi

Nickel recovery fromdilute solutionsElectron*inning of HareSartb. aSlectrodepos i t ion ofmetal/oxide composites

5Electroplating and

Electroforming

AK GroverHr DeshpandeA RamaaamyJT John

(SD)SB)

(3C)(SC)

Electroplating ofspecific metals andalloys.Electroforming ofspecial metallicparts.Elect rophoret icDeposition.

o

Ceramics Section0

Dr. 3.7.K. Hao, SOHead, Ceramics Section

ICeramic fuels and Special CeramicsDr. B.D. ZopeDr. Ashok Mohan2T.C. SoniSr. N.S. AnandanR. BhatP.K. AgnihotriP.V. George

Oxide Ceramics

(as)SD(SB)(3D)(GDI(so)

Ram Prasad v^s)3.N. Sharma (sc)

S.S.B.R.CM.G.E.G.T.S.

RoyVyasPathakPrasadKamathRamanathan

(SE(3D(S:D,(SDISC)(c)

Refractory SystemsDr. A.K. KullcarniPranab DasD.D. UpadhyayaE.T. DalviV.K.S. Hair

5A(3

Characterisation andsintering of 00 2, ThO3eO and UC,

2 '

Capacitor and ferr i teceramics. Developmentand evaluation ofBaTiO,, Ni-Zn-Ferritebodies and alliedsystems.

Develo.ui.-eat of V02 andU02-2r05 plats-typeFuels.Developmant of sinteredSiC as temperaturemonitors in irradiationexperiments.Development and fabrication of aluminacomponents for electrical applications andceramic fabrication.

Development of oeramic-materials for IHID.Hightemperature oxide ceramicsasAl2O, , ilgO forinsuli tion and rare-earth oxide stabilisedSrO2 for electrodes.

Development of A12O,catalyst carr iers .'uechani sins of sinteringand metallographie studies^Development of ceramicoxide solid electrolytes.

Refractory systems.R&B on refractorybodies as mullite,zircon, zirconiaand pyrophyllite andsteati te systems andhigh alumina substrates.

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SUPPOIZPIJG ASD ADilllJISTHAIIVB STAFFII.d. Jo sh i A/Foreman P.D. V/adawale /T.S. Shende T/E V.S. Kakhandaki T/DH.IJ. Barde T/3 Smt.L.K Santhappan Steuo ( S r . )

K.2. Yadav Helper A