One can get full description of metallic glasses which contains history, preparation methods, effects on metallic glasses, properties and application part is also there with diagrams, tables and graphs
2. CONTENT
Introduction
History
Classification
Preparation
Bulk metallic glasses produced by detonation gun spraying.
Melt-spinning technique for preparation of metallic glasses.
Processing metallic glasses by selective laser melting.
Thermal stability of BMG
Structure of BMG
Crystallization of BMG
Properties of BMG
Applications of BMG
3. INTRODUCTION
Newly developed engineering materials.
Glass is an amorphous, brittle and transparent solid.
amorphous
crystalline
High glass-forming ability
good castability
good printability
5. The durability of Ni-based glassy alloy gears
of 2.4 mm in diameter
• (Tensile strength)amorphous alloys ~ 3(tensile strength)crystalline alloys
• (Young’s modulus)amorphous alloys ~1/3(young’s modulus)crystalline alloys
(at same tensile strength)
• The slope of this linear relation corresponds to an elastic elongation
limit. This limit is measured to be about 2% which is about 3 times larger
than that (about 0.65%) for crystalline alloys.
• strength comes from the lack of slip planes on grain boundaries
6. HISTORY
The first reported metallic glass was
an alloy (Au75Si25) produced at Caltech by W.
Klement (Jr.), Willens and Duwez in 1960.
In 1969, an alloy of 77.5% palladium, 6%
copper, and 16.5% silicon - critical cooling
rate of 100 - 1000 K/s.
In 1976, H. Liebermann and C. Graham
developed a new method of manufacturing
thin ribbons of amorphous metal on a super
cooled fast-spinning wheel. Metglas(alloy of
Fe, Ni, P, B).
For example :- Metglas-2605 is composed
of 80% iron and 20% boron, has Curie
temperature of 373 °C.
7. (a) Thermoplastic processing in a Zr-Ti-Cu-Be bulk metallic glass. (b) Blow molding demonstrated in a Zr-Ti-Cu-
Be bulk metallic glass. (c) Capacitive discharge forming of a metallic glass showing the part and the mold in
which it was cast in 40 milliseconds. These are all demonstrations of thermoplastic processing.
Images from G. Duan and M.D. Demetriou.
8. In the 1990s new alloys were developed that form glasses at cooling rates as low as one
kelvin per second. These cooling rates can be achieved by simple casting into metallic
molds.
The best glass-forming alloys are based on zirconium and palladium.
In 1992, Vitreloy 1 was developed at Caltech, as a part of Department of
Energy and NASA research of new aerospace materials.
In 2004, bulk amorphous steel (actually rather cast iron owing to high C content)-"glassy
steel“- known by "DARVA-Glass 101".
Confusion effect :- Many amorphous alloys are formed by exploiting a phenomenon
called the "confusion" effect. Such alloys contain so many different elements that upon
cooling at sufficiently fast rates, the constituent atoms simply cannot coordinate
themselves into the equilibrium crystalline state before their mobility is stopped. In this
way, the random disordered state of the atoms is "locked in“.
9. In addition to direct cooling, there are several other ways in which amorphous
metals can be produced, including:
• Physical vapor deposition
• Extremely rapid cooling
• Solid-state reaction
• Ion irradiation
• Mechanical alloying
Amorphous metals produced by these techniques are, strictly speaking, not
glasses; however, materials scientists commonly consider amorphous alloys to be a
single class of materials, regardless of how they are prepared.
10. Physical vapor deposition
sputtering and evaporation
Zr-based Thin film BMG
Sputtering :- ejecting material
from a target that is a source onto
a substrate such as a silicon wafer.
Sputter - non-equilibrium –
amorphous structure
XRD pattern - Zr47Cu31Al13Ni9
2θ ~ 38º
amorphous Zr-Cu-Ti thin films can be obtained by adding 19% Ti
11. Solid-State Reaction
Diffusion couples combining a HCP Zr90Al10 supersaturated solid solution with a
FCC Cu64Ni36 solid solution were annealed at 410°C for different times.
Cu64Ni36 foils were prepared by the piston and anvil under high vacuum
conditions (p<10-3pa).
Zr90A110 alloy was rapidly quenched in between these two Cu64Ni36 foils, resulting
in a trilayer of approximately 150 pm thickness.
12. Mechanical Alloying
Mechanical alloying is performed in a planetary ball mill operated using stainless
steel vials and bearing steel balls in an argon atmosphere.
The amorphous powders were consolidated in a vacuum hot pressing machine
to produce bulk samples.
Cross section views of the milling vial of
(a) shaker mill and (b) planetary mill.
13. Changes in the material trapped between colliding balls in a
ball mill.
14. (a) BMG gears.
(b) Micrograph showing the teeth of a
BMG gear.
(c) Two BMG gears in a spur gear test
(d) Cast BMG gears integrated into a
working gearbox.
(e) cast BMG gears demonstrating the
ease with which they can be
fabricated.
15. CLASSIFICATION
o (Fe,Co, Ni ) and(B , Si, S, P )
o Nickel - Niobium (Ni-Nb )
o Magnesium-Zinc (Mg-Zn)
o Copper-Zirconium (Cu- Zr)
o Hafnium-Vanadium (Hf-V)
GLOBAL METALLIC GLASSES
16. PREPARATION
Various rapid cooling techniques are used for the production of metallic glasses
such as :-
o spraying
o spinning
o laser deposition
17. BULK METALLIC GLASSES PRODUCED BY
DETONATION GUN SPRAYING
•DOI: https://doi.org/10.1557/PROC-554-113
18. Detonation gun spraying of eutectic alloy containing iron, chromium, phosphorus
and carbon.
Thickness :- 2-3 millimeters.
Parameters studied :-
Heat capacity
coefficient of thermal expansion
corrosion resistance
Hardness
short range order structure
Amorphous detonation sprayed coatings - improve service properties of medical
instruments.
19. PROCEDURE :-
Amorphous coatings were produced by detonation spraying of Fe-Cr-P-C eutectic
alloy.
Detonation mixture - oxygen and acetylene. The gas detonation products are hot
enough to melt the powder particles.
Critical Cooling rate is 106 K/s or above.
An amorphous deposit can be used as a coating or constitute a part in itself.
23. Temperature dependence of the relative expansion/contraction
(a) strain and (b)the thermal expansion coefficient
during heating of the bulky amorphous sample and the thin ribbon
25. Melt spinning is a technique used for rapid cooling of liquids.
The cooling rates are 104–107 kelvins per second (K/s).
A wheel is cooled internally, usually by water or liquid
nitrogen, and rotated.
Large temperature difference solidifies into a ribbon.
The ribbon remains in contact with the disc surface up to 10
degrees arc and then leaves it under the action of the
centrifugal force.
26. A schematic diagram of the shape of the puddle and consequent ribbon formation when the
molten metal/alloy touches the surface of the rotating wheel.
27. The metal A is melted by induction coils I and pushed by gas pressure P, in a jet
through a small orifice in the crucible K over the spinning drum B where is
rapidly cooled to form the ribbon of amorphous material C
30. Operation mode - selective laser melting (SLM)
Ytterbium-fiber laser operating at a wavelength of 1070 nm and a maximum power
of 400 W was applied.
To reduce unwanted contamination the entire process takes place under a
protective atmosphere such as nitrogen, argon or helium.
31. Illustration of the SLM operating mode:
(a) a layer of powder is placed on the base plate.
(b) Then a high-power laser melts the powder in spots previously defined by a 3D CAD model
of the structure. The melt solidifies quickly and fuses with the structures below to form a solid
piece.
(c) Once the illumination process is finished the entire base plate is lowered, the next powder
layer is added and the process starts again at (a).
33. Thermal stability of BMGs
At present, the lowest critical cooling rate for BMG formation is as low as 0.10 K/s
for the Pd40 Cu30Ni10 P20 alloy.
The maximum sample thickness reaches values as large as about 10 cm.
The alloy with the largest supercooled liquid region of 135 K is
(Zr82.5Ti17.5)55(Ni54Cu46)18.75Be26.25
The quinary glass-former has distinct glass transition, very high stability of
supercooled liquid state, and exhibits high thermal stability against crystallization.
34. Vitialloy
Vitalloy 1(vit1) has the composition of Zr41Ti14Cu12.5Ni10Be22.5.
The critical cooling rates for glass formation in the 1 K/s range.
The formation of the BMGs in this family requires no fluxing or special processing
treatments and can form bulk glass by conventional metallurgical casting
Its GFA(glass forming ability) and processability are comparable with those of
silicate glasses.
The BMGs, which exhibit high thermal stability and superb properties, have
considerable potential as advanced engineering materials.
35. The picture of a cast vitalloy BMG system.
(prepared by the Institute of Physics, Chinese Academy of Sciences, China)
36. Six BMGs thermal parameters in relation to their thermal stabilities and
GFAs
37. A comparison of critical cooling rate and reduced glass
transition temperature Trg (Tg/Tm) for BMG, silicate glasses
and conventional metallic glasses.
38. The bulk metallic glass formers are very robust against some
heterogeneous nucleation sites at the surface or at interfaces. This leads to
the development of bulk metallic glassy matrix composites by the addition
of special crystalline materials.
A small change of Niobium(Nb) composition results in a substantially
improved GFA and ductility of the bulky glass-forming system.
Dissolution of minute amount of metalloid elements into the Zr–Ti–Cu–Ni–
Be metallic glass system can enlarge the thermal stability and hardness of
the BMG.
39. Structure of BMGs
There should be large differences in sizes leading to a complex structure which
crystallizes less easily.
A beryllium atom, for example, is much smaller than a zirconium atom.
Density measurements show that the density difference between BMG and fully
crystallized state is in the range 0.3–1.0%, which is much smaller than the
previously reported range of about 2% for ordinary amorphous alloys.
Such small differences in values indicate that the BMGs have higher dense
randomly packed atomic configurations.
40. The different atomic configurations of three types of BMGs
The Japan Institute of Metals.
42. Properties of BMGs
The strength of metallic glasses is very high but they are lighter in weight.
They are ductile, malleable, brittle and opaque. The hardness is very high.
The toughness is very high i.e. the fracture resistant is very high.
They have high elasticity i.e. the yield strength is high.
They have high corrosion resistance.
They do not contain any crystalline defects like point defects, dislocation, stacking
faults etc.
They are soft magnetic materials. As a result easy magnetization and
demagnetization are possible.
They have high electrical resistivity which leads to a low eddy current loss.
43. The relations between mechanical properties of typical BMGs:
(a) tensile fracture strength with Young’s modulus (E)
(b) Vickers hardness with Young’s modulus (E)
The Japan Institute of Metals
(a)
(b)
44. Compressive stress strain curve for cylindrical in situ composite specimen
The American Physical Society
45.
46. Applications of BMGs
The low magnetization loss is used in high efficiency transformers (amorphous
metal transformer) at line frequency and some higher frequency transformers.
Ti40Cu36Pd14Zr10 is believed to be non carcinogenic(not causing cancer), is about
three times stronger than titanium, and its elastic modulus nearly matches bones.
It has a high wear resistance and does not produce abrasion powder. The alloy
does not undergo shrinkage on solidification. These properties allowing better
joining with bones.
Mg60Zn35Ca5, rapidly cooled to achieve amorphous structure is used as
a biomaterial for implantation into bones as screws, pins, or plates, to fix
fractures.
47.
48. The high hardness is ideal for use in tooling. This property is useful in knives,
especially in scalpels.
High elastic energy storage per unit volume and mass, and the low damping, give
metallic glasses potential as springs.
Sporting equipment such as golf clubs and baseball bats utilize the high hardness
and elastic energy property for good energy transfer to projectiles.
Information storage and reproduction would utilize the lack of grain structure and
high hardness.
Features of near-atomic scale could be molded or etched into a metallic glass
surface to make masters for reproducing ultra-high density digital data.
50. The metallic glasses are used to make magnets which are used in levitated trains
(uses magnetic levitation to move vehicles without making contact with the ground)
Notes de l'éditeur
An amorphous metal (also known as metallic glass or glassy metal) is a solid metallic material, usually an alloy, with a disordered atomic-scale structure.
Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure.
More recently a number of alloys with critical cooling rates low enough to allow formation of amorphous structure in thick layers (over 1 millimeter) have been produced; these are known as bulk metallic glasses (BMG).
The product is non-magnetic at room temperature and significantly stronger than conventional steel, though a long research and development process remains before the introduction of the material into public or military use.
Amorphous metal ribbons have been produced by sputtering molten metal onto a spinning metal disk (melt spinning). The rapid cooling, on the order of millions of degrees a second, is too fast for crystals to form and the material is "locked" in a glassy state.
The lack of grain structure allows a blade to be sharpened to an exceptional edge because there is no length scale above the atomic to limit it.
