POLITEHNICA UNIVERSITY OF TIMIŞOARA

DEPARTMENT OF MATERIALS AND MANUFACTURING ENGINEERING

WE TRAIN THE BRAINS !

A NEW CLASS OF MATERIALS WITH HIGH POTENTIAL OF

ENGINEERING APPLICATIONS: METALLIC GLASSES

Prof.dr.eng. Viorel-Aurel Serban

Metallic glasses Definition

- Liquid presents an amorphous structure - Glass - an amorphous material - Glass - any material that can be cooled from a liquid to a solid without

crystallizing. - Most metals (M) crystallize as they cool

- Metallic glass (MGs) - metal with amorphous structure; crystallization does

not occur upon cooling from the melt i.e. “the liquid is frozen

Amorphous/glass - short range order

Crystalline materials

-long range ordered

metallic melt amorphous metal if- the diffusion speeds - very small - the viscosity- high the crystalline germs takes no place

for inhibit the crystallization

-favorable chemical composition range( thermodynamics factors) - critical cooling rate for amorphisation (kinetic factor)

Metallic glasses Definition

Angle θ Angle θ

Glass solid Crystalline solid

In

ten

sit

y

In

ten

sit

y

X-ray diffraction pattern

Fig. DSC curve Tg - the glass transition temperature ; Tm –the melting temperature; Tx - the crystallization temperature

Glass forming ability (GFA) Criteria : ΔTx = Tx-Tg high values T rg =Tg / Tm large ;

Metallic glasses(MGs) and Bulk Metallic Glasses (BMGs) Definition

high cooling rate small thickness limited engineering applications

to design very high GFA alloy four empirical rules (Inoue and Johnson) :

(I) multicomponent systems, (II) significant atomic size ratios above 12%, (III) negative heat of mixing and (IV) deep eutectic rule based on the Trg criterion.

can be made glassy into one or more millimetre-thick products

bulk metallic glass

( BMGs)

Families of amorphous metallic alloys

TM1-x

Mex ; x = 0.15-0.20,

• Fe-Si-B-Nb

• Fe-(Al,Ga)-(P,C,B,Si,Ge)

• Fe-(Cr, Mo)- (P,C,B,Si)

• Fe-(Cr,Mo)-(Al,Ga)-(P,B,Si)

• Fe-(Nb,Cr,Mo)-(C,B)

• Fe-(Zr,Hf,Nb)-B

• Ni-(Zr,Hf,Nb)-B

• Ni-(Nb,Cr,Mo)-(P,B,C)

• Ni-Zr-Ti-Sn-Si

• Ni-( Nb,Ta)-Zr-Ti

• Co-Fe-Si-B-Nb

• Ni-Si-B-Ta

• Co-(Al,Ga)-(P,B,Si)

(TM ) - (TM )

Zr-Al-TM

Ti-Zr-TM

Zr-Ti-TM-Be

Zr-(Ti,Nb,Pd)-Al-TM

Pd-Cu-Ni-P

Pd-Cu-B-Si

Ti-Ni-Cu-Sn

Cu- Ni- (P,S)

Cu- Ni-( Zr,Hf)-Ti

Cu-( Zr,Hf)-Ti-(Y,Be)

Cu-( Zr, Hf)-Ti-(Fe,Co,Ni)

Two categories of glass forming systems based on metals were discovered: a) Metal (TM )-Metalloid (Me) glasses b) Metal (TM )- -Metal (TM )- glasses

How to obtain a metallic glass(1)?

I. thin foils -splats - first metallic glass : Au80Si20 ( reported by Duwez – Caltech in 1960) - rapidly quenching from melt: cooling rate on the order of 106 K/s - splat- cooling process - piston-anvil technique

Inert gas Crucible

Molten alloy Piston/Anvil

Fig. Piston-anvil technique- representation

How to obtain a metallic glass(2)? (….our experience)

II. Thin ribbons up to 50 um thickness method :melt spinning process : planar flow casting

How to obtain a Bulk metallic glass(3)? III. Bulk metallic glasses

the first BMGs (since the 1980s ):

- rods with 9 mm diameter from La-Al-Ni and La-Al-Cu ternary alloys -reported by Inoue Group

from Tohoku University’s Institute , Japan

- sample with 15 mm thickness from Zr-Al-Ni-Cu (Vitreloys)- reported by Peker and Johnson from

Caltech, USA

Fundamental of fabrication quenching from melt with cooling rate on the order of 1- 102 K/ s

Methods : conventional casting techniques : injection/suction casting process

How to obtain a Bulk Metallic Glass? (….our experience)

3

2

1

4

5

a)

a)the copper mould casting setup b) the rod obtained by copper mould casting 1 - crucible; 2 - coil; 3 – copper mould; 4 – guiding device of the crucible; 5 – Ar pressure

Copper mould

How to obtain Metallic Glass coatings/plates (4)?

IV. Amorphous coatings with thickness up to 500 µm and amorphous plates measuring 1 to 10 mm in thickness

- Various technologies for deposition of surface coatings; most used : thermal spray methods

- Cooling rate in the range of 1-100 K/s

- Spray forming can be considered as an intermediate processing between casting and deposition

- amorphous metals coating by deposition of amorphous powders by HVOF/HVAF thermal spraying

-metals based amorphous plates by spray forming ( firstly fabricate from Al89La6Ni5 based BMGs and

Mg-Cu-Y(Gd) systems )

Fig. HVOF thermal spraying installation Fig. SEM micrograph of powders

SEM micrograph of coating

……Our results

Main scientific contributions

- Design of new amorphous alloys (as ribbon, wires, rods), for special industrial applications - some patented later - from Fe-Cr-P, Ni-Cr-Fe-Si-B, Cu-Ni- Sn- P, Zr-Cu-Ni-Al-Ti family etc.)

- Development of amorphous alloys for brazing of stainless steels, refractory steels and copper alloys.

- Development and characterization of nanocrystalline alloys by controlled devitrification of the amorphous phase methods

- Structural characterization, testing of mechanical, magnetic and chemical properties, microstructural analysis using modern equipment and investigations methods (scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, nanoindentation, cyclic voltammetry, sliding wear tests)

Metallic Glasses ribbons- production and characterization Fe75Cr5P12Si5C3 alloy Ni61Cr13Fe8Si10B7Co1 alloy

Ni61Cr13Fe8Si10B7Co1 ribbon

Hysteresis cycle of Fe75Cr5P12Si5C3 alloy XRD pattern for Fe75Cr5P12Si5C3 alloy

Alloy

Maximum

magnetic

susceptibility

max

Coercitive field

Hc [A/m]

Magnetic losses

P [W/kg]

Fe60Cr11Mo6Ni1Si12C6B3P1 112,9 1,15 0,013

Fe- Cr-Mo-Ga-P-B-C Bulk Metallic Glasses- production and characterization

Rod Fig. DTA curve of rod Fig. stress-strain curve of rod

Magnetic property as cast 450°C annealed

technical saturation magnetization

566 kAm-1

580 kAm-1

coercivity 400 Am-1 340 Am-1

magnetic remanence 288 kAm-1 303 kAm-1

initial magnetic susceptibility

977

1027

Fig. SEM micrograph of the fracture surface Fig. Hysteresis cycle of rod

Glassy powder Zr52.5Cu17.9Ni14.6Al10Ti5 Glassy powders Fe74Mo4P10C7.5B2.5Si2

SEM analyses of Fe-based glassy powders (1), Zr- based glassy powders (2), mixed powders (3)

Dual phase bulk metallic glasses (DPBMGs) Fe and Zr based production and characterization (1)

(1) (3)

XRD patterns

(2)

mixed by milling bulk consolidated by hot pressing

Fe and Zr based dual phase bulk metallic glasses ((DPBMGs) production and characterization (2)

Fig. DSC curves for bulk consolidated by hot pressing

SEM micrograph of the DPBMGs

Fig. DSC curves for mixed powders Fig. XRD patterns of powders

Why Glassy alloys could be the materials of future (1) ?

I. An unusual combinations of strength, ductility, toughness, and processability

a) mechanical properties

- High hardness and yield strength (can be - twice as strong as

steels)

- The high elastic strain limit

- Low mechanical dumping

- More elasticity and fracture toughness than ceramics

- Less brittle than conventional oxide glasses

- Very high resilience

b) technological properties

- high precision and finish in castings

- high thermoplasting forming

- good soldering and brazing

M. Telford: Mater. Today 7 (2004)

Why Glassy alloys could be the materials of future (2) ?

II. Magnetic properties

Fe, Co and Ni based Mgs and BMGs are soft magnetic materials

- with high magnetic permeability and saturation magnetization

- low coercivity field

- low magnetic losses (combine with high electrical resistance )

III. Remarkable soft magnetic properties ,high electrical resistivity , good wear and

corrosion resistance and biocompatibility

Applications

- Mechanical applications casings in electro-magnetic instruments and electronic equipment precision gears for micromotors automobile Valve Springs, diaphragms for pressure sensors structural parts for aircraft (Zr-based sheets and BMGs ). high torque geared motor parts,

- Magnetic applications transformers cores , sensors for magnetic fields, magnetic yoke for linear actuator ( Fe and Ni based alloys sheets and BMGs) magnetic–shielding for laptop PCs electronic,

- Various application Sporting goods and equipment- - golf clubs, tennis rackets Large amorphous sheets for under –floor heating Biomedical applications (scalpel blades, implants, blades for knives) Various shapes of optical mirrors

Application -own contributions magnetic shielding manufacturing from Fe75Cr5P12Si5C3 ribbons.

Magnetic screen

Screening capacity by measuring the inside magnetic field Magnetic shielding types

Fig. Magnetic hysteresis cycles of Fe75Cr5P12Si5C3 ribbons.

Application -own contributions protective shielding from Fe67Cr4Mo4Ga4P12B5C BMGs

XRD pattern Hysteresis cycle -detail

Application -own contributions Ni and Cu- based Amorphous Brazing Alloys

Ni61Cr13Fe8Si10B7Co1 MGs and. Cu75Ni7Sn5P13 MGs

Fig. DSC curves Fig. microstructure of

Cu- stainless steel joint

Fig. Stress-strain curves of the brazed joints

Fig Fracture surfaces

Industrial scale application of MGs sheets and BMGs products

• Wide strips /metal sheets of Fe-based alloys MGs

- used in transformers in the amorphous state or after heat treatments.

- manufacturing companies: Hitachi Ltd (Japan) and Vacumschmelze GmbH (Germany)

• Fe, Ni, Co-based MGs ribbons

- used for sensors , anti-theft protection tags

- manufacturing companies :ALPS Electric Co., NEK-TOKIN

• Fe-based amorphous powder (gas atomization)

- used for applications including coating and sandblasting

- manufacturing companies :Kawasaki Steel Corporation, Sanyo Special Steel , Japan

Industrial scale application of MGs sheets and BMGs products

• products from Zr-based BMGs , Ti-based BMGs

- used for parts “on demand” (cases, gears for micromotors, medical devices etc)

- manufacturing company: Liquidmetal Tehnologies ( USA)"

Challenges

I. Actually Fe based C-containing BMGs so-called bulk amorphous steels(BAS) with :

- Very high mechanical strength, very good ferromagnetic properties and high corrosion resistance

- BAS has broad application prospects in aerospace, automotive, precision manufacturing,

telecommunications and computer, biomedical area and so on

- A major obstacle to the development of Fe-C based BMGs (BAS) :

a) low GFA

b) relatively high fragility , very brittle in tension, reduced plastic deformation in compression

c) manufacturing costs (a high purity alloy is required ,good control of casting parameters

reduced reproducibility )

Challenges

- Requirement : to produce BAS by casting in copper matrix using ferro-alloys as raw materials with relative good deformation and reduced fragility ( to produce BMGs with two-phase microstructures( ductile metallic crystalline particles in MGs matrix or hard MGs particle in a ductile metal matrix) or to induce local fluctuations

II. Gearbox for space missions- MGs pinions with high wear resistance can work

without oil or other lubricant

III. Versatile biomedical implant applications from stents to tissue implants.(Schroers

imagines “custom-shaped implants,”) due to excellent combination of properties and

processing capabilities

instead of ... Conclusions

• Despite numerous investigations of the structural and properties of metallic glasses, they

still remain unintelligible. However, as the yield strength of bulk metallic glasses is up to

one order of magnitude higher than in polymers and the elastic strain limit is double that

found in conventional metallic alloys, it is likely that bulk metallic glasses or composites

will replace some conventional materials in our everyday life in the near future

Motto

…..If we allow the scope of academic research to continue to be narrowed to fit the

wants of industries and politicians , what we will have is a nation built on narrowly

focused, relatively unsustainable, wasteful, even dangerous policy … The academy is …

the last place …where truly independent research can be conducted “ The Chronicle of Higher Education /Take Back the Ivory Tower By Alice Dreger