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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