__.. ,_ -r___

STATES

.. AMRA CR 66-10:1-3

FIESE

DIFFUSION BONDING OF

TITANIUM ALLOYS

Third Quarterly Report

By

C. A. Smith D D CE.L. Reed r,. i.r - "

U OCT 26 19671j

May 1, 1967 1 ,

C

ATOMICS INTERNATIONAL

A Division of North American Ayiation, Inc.

Canoga Park, California

Report No. AI-67-137Contract No. DA-19-066-AMC-339(X)

Distribution of this document is unlimited.

U. S. ARMY MATERIALS RESEARCH AGENCYWATERTOWN, MASSACHUSETTS 02172

C L A P I N 4H U

ns i IAI 1:

The findings in this report are not to be Construed asan officiel Deportment of the Armny position, unless Sodesignated by' other authorized documents.

Mention of any trade, names or manufacturers in this reportshall not be construed as advertising nor as an officialindorserwent or oaprovol of such products or companies bytWu United States Government.

DISPOSITION INSTRUCTIONS

Destroy this report who,, it is no longer needed.Do not return it tuj the originator.

DIFF".'ZON BONDING OF

TITANIUM ALLOYS

AMRA CR 66- '0/1-3

BY

C. A. SmithE. L. Reed

May 1, 1967

ATOMICS INTERNATIONALA Division of North Americcan Aviation, Inc.

Canoga Park, California

Report No. A 1-67-137Contract No. DA- 19.066-AMC-339(X)

Distribution of this document is unlimited.

U. 5P ARMY MATERIALS RESEARCH AGENCYWATERTOWN, MASSAVIUSETTS 02172

ABSTRACT

The program attempts to develop an understanding of the diffu-sion bonding of titaniui. alloys; in partic-lar, the alloy Ti-6A-V.Me accomplishments of the third quarter of the program are asfollows:

1) A series of tensile and bend tests has been comtpleted.tLese te.ts showec trends which were in reasonable

agreement with the shear tests porformed during thesecond quarter.

2) Additional shear tests have been perform- to extendthe range of variables to grea t er pressures and shorterbonding ties thln those reported for the seco~id quarter.

3) Examination of bond line photomicrographs indicates acorrelation between bonded length and relative tensilestrength. This correlation may find practical use inestimting bond quality.

A:-67-137

2

CONTENTS

Page

Abstract . ........... ..... . . . ... .. 2

I. Tensile and Bend Tests ..... ..... . ... . ...

A. Preparation of Specimens ................... 5

B. Room Temperature Tensile Tests. . . . . . . . . 6

C. Room Temperature Btnd Tests . . . . . . . . . . . . 7

II. Shear Tests ....... ....... ......................... . 8

Iii. Plans for the Fourth Quarter ............... . . . 9

FIGURES

1. Details of Graphite Fixture with Bonded Specimens in Place . • • 12

2. Assembled Graphite Butt Bonding Fixture with Top Plate inPlace for Dead Weight Loading . . . .............. 13

3. Photograph of Ti-6AI-4V Alloy 3pecimens Before and AfterButt Diffusion Bonding ...... ........................ 14

4. Photograph of Ti-6AI-4V Alloy Specimens After Butt DiffusionBonding . . . . . . . . . . . . . . . . . . .. .. . . . . 15

5. Tensile Test bpecimens Machined from Butt Diffusion BondedSpecimens I.

6. Butt Piffusion Bon('ed Specimens After Poon TemperatureTensile Testing ......... ........................ ... 17

7. Rn 3S. Bonding at 1600OF ...... ............ 18

8. Run 5S. Ponding at 1600F ......... ..... ..... . 18

9. Run 2S. Bonding at 1700OF ......... ...... .... 19

10. Run 63. Bonding at 17OF ... ............ ... 19

Ii. Run 3S. Bonding at 1600&F.......... .. .......... n

12. Run 5S. Bonding at 16000F ......... ..... .... . 20

13. Run 2S. Bonding at 17000F ......... ..... ..... 21

14. Run 6S. Bonding at 17000F ......... ..... ..... 21

15. Run iP. Boring at 1640OF ......... .. ....... 22

16, Run 2HP. Bonding at 16400F .... ............ ...... 22

17. un 3HP. Bonding at 154COF .... ................. 23

18. Run 3HP. Bonding at 154 0 F . . .... . . . . . . .. 23-

AI-67-1373

TABLES

Page

1. Room Temperature Tensile and Yield Strength of Butt Diffusion

Bonded Ti-6Al-4V Alloy Specimens 10

2. Bend Strength of Butt Diffusion Bonded Ti-6AI-A4V Specimens . . .

3. Shear Strength of Ti-6A1- 4V Alloy Diffusion Bonded SpecimensCompared wiuh Pacent MeLal S.regt .. ............. ..

Al-67-137

4

I. TF2SILE AND BEND TESTS

A. PREPARATION OF SPECIMFNS

The preparation and testing of eight butt diffusion bonded Ti-6Al-4V alloyspecimens was completed during L.he quarter. 'etails of 'he gr, ite toolingfixture uscd to hold the specimens during bonding are shcwn in Figures 1 and 2Figure 1 shows the graphite tooling with two bonded spec,n r3 in place after atypical run. The 4hite base plate is an alumina ceramic used to support thefixture during the bonding cycle. A photograph of the vacuum furnace used fordiffusion bonding was exhibited in the first quarterly report.* Figure 2 showsthe fixture assembled -with tne top load plate in place. Stainless steel weightswere placed on top of the load plate after the assembly had been placed insidethe furnace. The total weight of the top plate and rings was adjusted to obtaina 3pecimen bonding pressure of 100 psi.

Figure 3 shows typical pieces of the titanium alloy before and after buttdiffusion bonding. The bonded specimen on the right shows a bond line at theJoint because of a slight bevel on the edges. The surfaces were ground toremove any surface imperfection at the joint interface.

Specimens were butt diffusion bcnded undar the following sets of conditions:

Butt Diffusion Bonding Runs

Spec. Best and Poorest

No. Bonding Conditions Vacuum Readings Remarks

J 1500"F-I Hr.-100 psi 2 x 10- to 8 x 10- Torr No bond obtained

4S 15O0CF-I Hr.-iOO psi 7 x 10 to 4 x iO-5 V,-y .r bond

35 160 -I Hr - CI psi 2 x 10 5 to 4 x 10-5 3 onci ad

515 i&tXZ)F-4 Hr.-100 psi ! x .0 3 x 10- Bonded.

27 iT0)F-1 hr.-!OC psi 2 x 10- to 6 x 10 Bonded

65 1700F-4 Hr.-100 psi 2 x 10- to 5 x 10- Bonded

Little or no bonding w - achieved at 1500-.F but good appearing bonds wereobtained at 160"F and 170°F. Figu~re . shows four specimens that were boriedat 1.600'F and four specimens that were bonded at 1700°F. iNte that the bond

4 nith, C. A., and Reed, E. L., 'Piffusion Bonding of Titanim Alloys, FirstQuarterly Rep)rt. U.S. Armq Materials Research Agency Report No. CR66-Ic/I.

Al-67-1175

line is visible in the center of each specimebo. After 1rinding to remove theslight edge bevel the bond lines were no longer visible .o the naked eye. Onczpecimen fram each set of bonding conditions was machined into tenslle specimens.Figure 5 shows a photograph of these specimens before tensile testing. Note thatthe bond interface is no longer visible dfter surface grounding and machining.Figure 6 shrews these specimens after tensile testing. The small black circleson three of the specimens outline the 2 in. gauge marks that were used todetermine total elongation. Gauge marks also are visible on specimen 6S.

B. ROOM TEMPERATURE TrYSiLE TESTS

The results of the tensile tests are listed in Table 1. Soecimen 33-Bbonded at !600OF for one hour showed poor tensile strength 2nd no elongation,but four hours bonding time at 1600OF (Spec. 5S-B) resulted in a significantstrength improvement even though the elongation was still nil. (The specimenpressure in these butt diffusion bonding tests was the same as for the majorityof the specimens diffusion bonded in tie vacuum hot press equipment.) Bondingat 1700F for either one hour or four hours produced joint tensile strengthsgreater than 90 percent of the parer metal strength. Four hours at 17(0Fresulted in an ultimate tensile strength increase of 4,300 psi as compared withthe sa.aple bonding cycle of one hour at 1700F. Both of the specimen, bondedat 1700'F showed 13% elongation in a gauge length of 2 in. compared with 1!.8%for the par-ent metal.

Small pieces of the alloy were cut from the joints of the tensile specimensbefore they were machined. The microstructure of these different specimensshowed an interesting corrvlation of bond appearance with the ultimata Jointtensile strengths. Figures 7, 8, 9 and 10 show photomicrographs of these joints.Portions of these same areas are shown at a magnification of 500X in Figures ii,12, 13 &nd 14. Referring first to the photonicrographs at lOOX observe that inFigure 7 there are very few areas sho,-ing bonding e ross the interface aftelbonding it 16000F for one hour. Here the ultimate tensile strength of the bondwas only 49,7(0 psi. figure q shows a number of areas in the sample that werebonded at "L600F for four hoiurs where complete bonding across the interface

a occurred; the resulting Joint strength was increased to i22,>JO psi.Similarly, in F-gure 9 ory a few nbonded spots are visible and the bondstrength hzs increased to 133,.)0 psi, while in Figure 10 onli two or threevery sali unbonded spot s are perceptible. Here the ultimate tensile strengthwas 137,50C psi, or 4.7 of the parent meta& strength.

A c coarison of the microstructures with the corresponding Joint strengthsis even more st'iking at 5CDX (Figures 11, 12, 13 and 14). A rough approydma-tion of the percent of bonded length was made from each photoi.ncrog'apch. Theresults are listed below and compared with the rcent of parent meta' ultimatestrengthm observd:

AI- T'-i3 7

6

No. _3ondj~y Param~eters B nd Mtal Jtrength

Theseresulex'or'wa benI corelto ogdrn h hr egh fbn

lPn roisximum atn loa txX.d

Roo sepec-r bend tkess wen incesm-lo h cn e.o pcmn

f.oite that th difusion bonding sri3s Palendtwt were madefcatl onhe thr.teeopensrinsfie parent alues, -4 4,rt 1-ory for the w~ent ma.et,&I nd finith gtd tthesane at l7CC'ion'Fa the bondavio sntmens alh rtof uthse tests arehownvr in Tales e inaso~e n he srnh nowedxhe an e pattrafothec ens3il tests A3 end h slliOf 3. ices bwas used ductility fkbrittl.steagt a aluaa fc. r)., oliwn frua

Ai b-l3

II. SHEAR TESTS

Shear tests were performed on two specimens hot press bonded at 650 psi for

one hour at 1540 and 1640"F, respectively. Also two specimens wore hot pressbonded at 100 psi for 1/2 hour at 1440OF and at 1470F. The latter specimenswere prepared to fill in an apparent gap in the deformation (vs.) shearstrength curve presented in the last report. The average i-ar strengths ofthise cecimens and t-e ., 6ar strengths of the respective parent metal specimensare shon in Table 3. Specimen deformations also are lieted. Note that the650 psi runs showed a large amount of specimen deformation and joir. strengthsequivalnt to those of the respective parent metal pieces. The specIaens bondedat low pressure for short times thowed the same aioimu of specimen deforation(0,0025 in.), yet considerable di:fi %nee was observed in their average shearsi rength values.

Figures 15 and 16 show the microstructure of a section of specimen 2 HP atlOOX and at 500X magnification. Similar photomicrographs of a section ofspecimen 3 HP are shown in Figures 17 &id 18. Complete b -iing and grain growthacross the interface is evident i. hoth specimens.

AI-67-1378

III. PLANS FOR THE FOULTh QUAMTI-R

No laboratory wo& is contemplated for the fourth quarter. Data analysisand work on the mthwatical model w-i continue. Preparation of the topicalreport will begin.

I

AI-67-137

9

I

TABLE 1

ROOM T PERATURE TE-SITE. ANTD YIFD STRINGTHOF BUTT DIFFUSION BONDED Ti-6AI-4V ALILY SPECI-NS

PercentSpecimen Bonding Conditions Elongation Yield Ultimate oi ParentNuber % in 2 in.) (0.2% Offset) Tensile Metal

(U.T.S.

3S-B !600*F-I Hr.-100 psi None None 49,700 psi 34.2%

53-B 1600*F-4 Hr.-lOO psi None Noie 122,300 84.2

23-B 17OO'F-.L Hr.-OO psi 13-0% 130,601 psi 133,200 91.7

63-B 1700'F-4 Hr.-100 psi 13.0 * 137,500 94.7

Parent Untreated 11.8 137,900 145,00" lOO.OMetal

• Extensometer failed. No data obtained.

• Average of three specimens.

p

AI-67-13710

TABLE 2

BE D STR.NGTH 01' BUTT DIFFUSION BONDFI Ti-6A1-4V SPECIMENS.SPECIMEN DIME-N5ONS 1.0 WIDE BY 7.6", LONG BY 0.16" ICK.

BEND SPAN, 3.0 INCHES.

Specimen 'Bend Load Flexural Percent of ParentNunber Bonding Conditions at Failure Strength Metal Strength

3S-A 1600°F-1 Hr.-100 pci 227 lb 44,900 psi 17.8%

5S-A 16001F-4 Hr.-100 psi 472 120,900 48.0

23-A 1700°F-i Hr.-100 psi 754 186,50C 74.0

63-A 1700*F-4 Hr.-100 psi 812 200,800 79.7

Parent Untreated 1407" 251,800 100.0Mtai

* Average of three 3pecimens.

TABLE 3

SHEAR STRENGTH OF Ti-6Al-4V ALLOY DIFFUSION BONDFD SPECIMENSCOMPARE WITH PARENT METAL STPENGTH

SShear Strength Shear Strep gh ofSpec4 rn Bonding Conditions of Joint Parent F al

(Avg. of 4 Tests) (Avg. of 4 Tests)

2 HP 1640OF-1 Hr.-650 psi 89,500 psi 89,300 Psi 0.56"

3 HP 1540OF-1 Hr.-650 psi 81,470 83,300 0.034"

LP 1 14700F-i Hr.-lY psi 17,900 92,200 0.0025"

LP 2 J44O°F- Hr.-100 psi 24,150 95,200 0.0025"

AI-67-13711

L___...... ............................................. ...Jl !. .

Figure 1. Detailc of (Ira, ite Fixture with BondedSpecimensi in Place

AI1-7-13712

Figure 2. Assembled Graphite Butt Bondiing Fixture with TopPlate in Place for Dead Weight Loading

AI-67-13713

Figure 3. Photograph of' Ti-6A1-4V Alloy Specimens Before aridAfter Butt Diffuiion Bonding

A-i-67--237

14

F-gure 4. Photograph of 'PI-6A1-4V Alloy Specimens AfterButt Diffusion Borxiing

A-1-67-13715

F- gu,-e 5. ri P ecl-mer Machired- fri~ F" u.tli-usl on' ne

AT-jt7 - 127

it,

1600 4600 1W GSg

r'igue 5. hdtt iffuson Bndred SpecLrnens After 7? oc m prtueTnil et

" ;I. ~ 'o

~-on

U n d

Ti -6A--V

Fgure 7. ' 3( Ponding at 16OC~ 00 ,--iile >'trength: 49)/7AD psi.

Fthe.lo%

22 , A'.~i s.,

T'i-6Al-l+V

Line

p'r c 9. 1 ~..~ a ?'Y ' CC I~i Hour.e~>~e 3rn -,CC 7s-.

1 5 CCA1 '4

c' Id

Linme

i'-6Ai-4V

Figure 11. Run 3S. Bording at 1600'F; 100 psi; 1 Hour.Tensile Stren~gth: 49,700 psi.Mc t- '443-1-2. Etched. 500X.

Ti4Al-4v

Line

Wi I U-W~-4V

Fiur Id. Ru 5S odn't10';1upi lus

Figure12. TRnsl 53. ondngt 12200 -)u si; 4ous

Met.-7443-2-2. Etched. 500X.

Ai-67-137

20

II ri

-- ,

- -i ...,, 4.

: - Bond

Line

Ti -6A!-4V"

Fig-are 13. in 23. P'nding at 1700F; ]00 psi; 1 Hour.Tensile Strength: 133,200 psi.Met.-7443-3-2. tched. 500X.

- S

?Ti-6A.14V

Figure 14. Run 6S. Bonding at 17000F; 100 psi; 4 Hours.Tensile Strength: 137,500 psi.Met.-73-4-2. Etched. 50OX.

AI-67-137

21

Ti - 6,,1 - 4 v

Ti-6A1-4v

Figure 15. Run ZiP. Bonding at 1640'7; 650 psi; I. Hour.Shea, Strength: 89,520 psi.

Met.-7444-1-1. Etched. 1QOX.

Ti-6Al-4v

.* Bond*-Line

Figure 16, Run 2HP. Bonding at 16400OF. 650 Psi; 1 Hour.Shear Strength: 89,520 psi.

Met.-74.44-1-2. Etched. A5OX.

AI-67-13722

BondLine

Figure 17. Run 3HP. Bonding at 1540OF; 65 psi; 1 Hour.Shear Strength: 81,470 psi.

Met.-7444-2-1. Etched. 100OK.

BondLine

Figure 18. Run 3HP. Bonding at 1540O ; 650 psi; 1 Hour.Shear Strength: 81,470 psi.

Met.-71J4-2-2. Etched. 500X.

A 1-67-13723

Uacla i sified |

- Classification

(- .... DOCUMENT CONYROL DATA- R&D -O0"Itlefor toal N"08 of W t, body of AbtractIa.nde inara.E .anfdlioan ~0 Ijt bored *-n fe, aUt*r gll repoa ig aslseed)

04146111A ~~~~ ~ *c meATVT cmofe U6 F tPOT 611CU6Ir C LA961ICTIO 1N

Atolics International Unclassified __---8900 DeSoto Avenue Ia OdCanoga Park, Califorr.ia ot Applicgble

J. REOR TITLE oApicbl

DIFFUSION BONDING OF TrVANIUM A7 %YS

4. 016C111gryIVE MOTUS (Typel 1prl and Mchuu ste, -ata*)

Third Quarterly Report (Decembi 1, 1966 to February 29, 1967).

S. AUTHOR(S) (Leet 1100 Smir 110100 initil)

Smith, Curtiss A. and Reed, Edward L.

.IPOR VI ATE 78. TOTAL"&O OF 9DAaS 7!1 No. or acps

S. RACY May 1, 1967 230. ZONTRACY ON $RANT NO. 90. ON11HATOR'S REPORT NUM89[t(S)

DA-19-066-AMC-330 'x)(PROJECT WO. AMRA CR 66-10/1

a. 96. ITNS RIPORT NC(S) (Any.Utewr.a~ore Mae me- be &@signde.

d- AI-67-137

M0O A V A IL4 AILITY/LIITATION NOTICES -

Distribution of this documant is unlimited.

1 . SUPPL EMTARY NOTS SPONSORING MILITAiY ACTIVITY

Araq Materials and Mechanics Research CenterWatertown, Massachusetts 02172

11 ABSTRACT

The program attempts to develop an understanding of the diffusion bonding "ftitanium alloys; in particular, the alloy Ti-6A1-4V. The accomplishments of thethird quarter of the program are as followe"'

1) A series of tensile and bend tests has been completed. Thesetests showed trends which were in reasonable agreement with

the shear tests performed durig the secofd quarter.

2) Additional shear tests have beer perfor-med to extend the rangeof variables to greater pressures and shorter bonding times thanthose reported for th%. second quarter.

3) Examination of bond line phoLomicrbgraphs indicates a correlationbetween bonded length and relative tensile strength. This

correlation maj find practical use in estimating bond quality.

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