Youngsmodulus, E (GPa)

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Advanced Physical Metallurgy Advanced Physical Metallurgy

“ “ Amorphous Materials Amorphous Materials ” ”

Eun Eun Soo Soo Park Park

Office: 33-316

Telephone: 880-7221

Email: espark@snu.ac.kr

Office hours: by an appointment

2009 spring

03.04.2009

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2

Contents for previous class Contents for previous class

• Amorphous Amorphous – from the Greek for “without form”

not to materials that have no shape,

but rather to materials with no particular structure

• grain boundaries

nearly random = non-periodic

• no grain boundaries

Building block: arranged in orderly,

3-dimensional, periodic array

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3 σ/E=

10^-4

10^-3

10^-2

10^-1 σ²/E=C

Elastomers Polymers

Foams

wood

Engineering Polymers Engineering

Alloys

Engineering Ceramics

Engineering Composites Porous

Ceramics

Strength σ_y (MPa)

Youngsmodulus, E (GPa)

< Ashby map >

0.1 1 10 100 1000 10000

0.01 0.1

1 10 100 1000

Amorphous metals

Contents for previous class

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Contents for previous class Contents for previous class

composite Metals

Polymers

Ceramics

Amorphous materials

Elastomers

Menu of engineering materials

High GFA

High plasticity

higher strength

lower Young’s modulus high hardness

high corrosion resistance good deformability

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Contents for previous class Contents for previous class

Microstructure

Microstructure - - Properties Relationships Properties Relationships

Microstructure Properties

Processing

Performance

Design Design

“ “ Tailor Tailor - - made Materials Design made Materials Design ” ”

(6)

Contents for today

Contents for today ’ ’ s class s class

Introduction to Amorphous Materials

•

Glass Transition Temperature

•

History of Amorphous Metals

•

Glass Formation

•

Introduction to Amorphous Materials

•

Unique Properties of Amorphous Materials

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Introduction_amorphous

Introduction_amorphous materials materials

Amorphous materials

a wide diversity of materials can be rendered amorphous

indeed almost all materials can.

- metal, ceramic, polymer

ex) amorphous metallic alloy (1960) - glassy/non-crystalline material

cf) amorphous vs glass

- random atomic structure (short range order) - rapid solidification from liquid state

- retain liquid structure

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Glass:

Glass: undercooled undercooled liquid with high viscosity liquid with high viscosity

Crystal Transition glass Transition

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Effect of cooling rate on glass transition temperature

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Introduction_amorphous

Introduction_amorphous metals metals

Definition of metallic glass

• Noncrystalline metallic solid lacking long-range periodicity of atomic arrangement and showing glass transition.

Bulk metallic glass (BMG)

• Metallic glass having a minimum dimension of 1mm which is equivalent to a critical cooling rate of about 10³ to 10⁴ K/s.

Glass Formation

• Competing process between retention of liquid phase and formation of crystalline phases

a. Liquid phase stability

- Stability of the liquid in the equilibrium state (i.e. stable state, Tl) - Stability of the liquid during undercooling (i.e. metastable state, Tg) b. Resistance to crystallization

- Nucleation and growth of the competing crystalline phases

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Thermodynamical aspect

Small change in free E. (liq. cryst.)

Thermodynamical aspect

Thermodynamical aspect

Small change in free E.

Small change in free E. (liq. cryst(liq. cryst.).)

Kinetic aspect

Low nucleation and growth rates

Kinetic aspect

Kinetic aspect

Low nucleation and growth rates

Low nucleation and growth rates Structural aspect

Highly packed random structure

Structural aspect

Structural aspect

Highly packed random structure Highly packed random structure

Glass formation Glass formation Glass formation

Formation of crystalline phases Formation of crystalline phases

Formation of crystalline phases

Retention of liquid phase

Retention of liquid phase

• Suppression of nucleation and growth of crystalline phase

• Higher degree of dense random packed structure

High glass-forming ability (GFA )

••

Suppression

Suppression of nucleation and growth of crystalline phaseof nucleation and growth of crystalline phase

•• HigherHigherdegree of dense random packed structuredegree of dense random packed structure

High glass

High glass- -forming ability forming ability ( (GFA GFA )

^∝ ¹^/ ^R^c ^or ^Z^max

)

Glass formation

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History: amorphous metal History: amorphous metal

1934 Vapor deposition

1950 Electro-deposition: Ni-P alloy

: hard & corrosion resistant coating 1960 P. Duwez (Caltech)

- quenching: phases stable at high temperature

- retain at R.T. / transform into other metastable phases - in solid state

- quenching from liquid state

(breakthrough)

- eutectic system : α + β

- rapid quenching: complete solid solution ? : Hume Rothery rule

(1959) complete solid solution (but, crystalline)

Formation of solid solution depends on

the size difference, electronegativity, crystal structure.

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Glass formation: stabilizing the liquid phase Glass formation: stabilizing the liquid phase

First metallic glass (Au₈₀Si₂₀) produced by splat quenching at Caltech by Pol Duwez in 1960.

W. Klement, R.H. Willens, P. Duwez, Nature 1960; 187: 869.

2 . 0

* − ≥

=

Δ mix

Tm

Tm mmix

T T

in most of glass forming alloys

by I.W. Donald et al, J. Non-Cryst. Solids, 1978;30:77.

- Relative decrease of melting temperature

(where, ,

= mole fraction,

= melting point)

∑

= _i _mⁱ

mix

m xT

T

xi i

Tm

Au Si

0 10 20 30 40 50 60 70 80 90 100 100

300 500 700 900 1100 1300 1500

18.6

363 1064.4

1414 Liquid

Temperature (°C)

deep eutectic ΔT* = 0.679

Rapid splat quenching

liquid metal droplet laser trigger

metal piston metal anvil

t = 20 μm l = 3 cm w = 2 cm T_m^mix

T_m

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Glass formation: stabilizing the liquid phase Glass formation: stabilizing the liquid phase

1969 Ribbon type with long length using melt spinner : FePC, FeNiPB alloy

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Bulk formation of metallic glass Bulk formation of metallic glass

First bulk metallic glass Pd_77.5Cu₆Si_16.5(T_rg=0.64) By droplet quenching (CR~800 K/s)

H.S. Chen and D. Turnbull, Acta Metall. 1969; 17: 1021.

SEM image of a collection of glass spheres

Alloy Selection: consideration of T_rg

Pd₄₀Ni₄₀P₂₀(T_rg=0.67)

Suppression of heterogeneous nucleation

Largest ingot

- minimum dimension 1 cm and mass of 4 g - Critical cooling rate: ~ 1K/sec.

Drehman, Greer, and Turnbull, 1982.

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Recent BMGs with critical size

Recent BMGs with critical size ≥ ≥ _{10 mm} _{10 mm}

Zr₄₇Ti₈Cu₈Ni₁₀Be27 Johnson (Caltech) Vitreloy

Pd₆₀Cu₃₀Ni₁₀P₂₀ Inoue (Tohoku Univ.) Fe₄₈Cr₁₅Mo₁₄Y₂C₁₅B₆ Poon (Virginia Univ.)

Amorphous steel

Ca₆₅Mg₁₅Zn₂₀ 15mm Kim (Yonsei Univ.) Ca₆₀Mg₂₅Ni₂₀ 13mm

Mg₆₅Cu₂₀Ag₅Gd₁₀ 11mm

Mg₆₅Cu_7.5Ni_7.5Zn₅Ag₅Gd₅Y₅ 14mm

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 1) very soft magnetic material

- low magnetic loss

- 8 0 8 16 24 32 40 48 56 64 72 0

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

1.8 Conventional- 0.28 mm thick

Amorphous Fe₈₀B₁₁Si₉ 30 um thick

Magnetizing Field (H), A/m

Induction (B), Tesla

Transformers

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 2) very hard, high strength

Al alloy Ti alloy

Al alloy Ti alloy Stainless BMGStainless BMG (Liquidmetal(Liquidmetal^®^®))

Yield Strength [ 1,000 psi ]

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 2) very hard, high strength

very brittle

Wcadcg]hY

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 3) large elastic strain limit

Elastic Strain Limit

[ as % of Original Shape ]

Al alloy Ti alloy Stainless BMG Al alloy Ti alloy Stainless BMG

(Liquidmetal(Liquidmetal^®^®))

0.5 % 2.0 %

Strain, ε

2000

1500

1000

500 0 Stress σ(MPa)

Stainless steel

BMG

Stress-Strain Curve

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Stainless BMG Ti alloy

22

(Liquidmetal(Liquidmetal^®^®))

Bouncing bearing on Liquid Metals

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 4) thermal expansion coeff.: ~ zero

T_melting T_g

Molar Volume, V

Liquid

Glass formation:

continuous change

Crystal Glass

Temperature, T

Crystallization:

abrupt change

Near-net shape production

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all

5) electrical resistivity

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Allotropes of carbon

ex) diamond ex) carbon

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Allotropes of carbon

Eight allotropes of carbon: diamond, graphite, lonsdaleite, C60, C540, C70, amorphous carbon and a carbon nanotube.

http://en.wikipedia.org/wiki/Allotropes_of_carbon

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all

3~4 times higher than crystalline alloy

5) electrical resistivity

Crystalline carbon (graphite) Amorphous carbon

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 6) corrosion resistance

Crystals Liquids, glasses

• grain boundaries • no grain boundaries

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- Grain boundary corrosion

SEM micrograph

showing severe grain boundary corrosion

The sensitized structure lends itself to intergranular corrosion as shown below.

(Left) Optical micrograph showing intergranular corrosion from the outer diameter to sub-surface.

(Right) SEM micrograph of the same region.

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 6) exceptionally high corrosion resistance

Crystals Liquids, glasses

• grain boundaries • no grain boundaries

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Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

- not shared by crystalline solids at all 1) very soft magnetic material

- low magnetic loss 2) very hard, high strength

very brittle

4) thermal expansion coeff.: ~ zero 3) large elastic strain limit

5) electrical resistivity

3~4 times higher than crystalline alloy

6) exceptionally high corrosion resistance

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(34)

Alloying: atoms mixed on a lattice

Solid Solutions and Ordered Compounds

Two Possibilities for Solid Solutions: B atoms in A atoms

Substitutional Interstitials

‘

new element replaces host atoms’ ‘new element goes in holes’

Can we roughly estimate what atoms will form solid solutions?

e.g. semiconductor devices:

doped-Si C in Fe e.g. Ni in Cu, steels

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Ordered Substitutional and Interstititials Compounds

Substitutional Interstitial

element replaces host atoms element goes into holes in an orderly arrangement in an orderly arrangement

e.g., Ni₃Al (hi-T yield strength),

Al₃(Li,Zr) (strengthening) e.g., small impurities, clays ionic crystals, ceramics.

Alloying: atoms mixed on a lattice

Solid Solutions and Ordered Compounds

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• Solid solution of B in A plus particles of a new phase (usually for a larger amount of B)

Second phase particle --different composition --often different structure.

Particles of New Phase in Solid-Solution Alloys

Solid Solution phase B atoms in A

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Hume-Rothery Rules for Alloys (atoms mixing on a lattice)

Will mixing 2 (or more) different types of atoms lead to a solid-solution phase?

Empirical observations have identified 4 major contributors through :

+1 +2

Atomic Size Factor , Crystal Structure, Electronegativity, Valences

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Hume-Rothery Rules for Mixing

Empirical rules for substitutional solid-solution formation were identified from experiment that are not exact, but give an expectation of formation.

Briefly,

1) Atomic Size Factor The 15% Rule

If "size difference" of elements are greater than ±15%, the lattice distortions (i.e. local lattice strain) are too big and solid-solution will not be favored.

DR%= < ±15% will not disallow formation.

2) Crystal Structure Like elemental crystal structures are better

For appreciable solubility, the crystal structure for metals must be the same.

3) Electronegativity DE ~ 0 favors solid-solution.

The more electropositive one element and the more electronegative the other, then

"intermetallic compounds" (order alloys) are more likely.

4) Valences Higher in lower alright. Lower in higher, it’s a fight.

A metal will dissolve another metal of higher valency more than one of lower valency.

r_solute − r_solvent

r_solvent x100%

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Is solid-solution favorable, or not?

• Cu-Ni Alloys

Rule 1: r_Cu = 0.128 nm and r_Ni= 0.125 nm.

DR%= = 2.3% favorable √

Rule 2: Ni and Cu have the FCC crystal structure. favorable √ Rule 3: E_Cu = 1.90 and E_Ni= 1.80. Thus, DE%= -5.2% favorable √ Rule 4: Valency of Ni and Cu are both +2. favorable √

Expect Ni and Cu forms S.S. over wide composition range.

At high T, it does (helpful processing info), but actually phase separates at low T due to energetics (quantum mechanics).

Hume-Rothery Empirical Rules In Action

r_solute − r_solvent

r_solvent x100%

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Is solid-solution favorable, or not?

• Cu-Ag Alloys

Rule 1: r_Cu = 0.128 nm and r_Ag= 0.144 nm.

DR%= = 9.4% favorable √

Rule 2: Ag and Cu have the FCC crystal structure. favorable √ Rule 3: E_Cu = 1.90 and E_Ni= 1.80. Thus, DE%= -5.2% favorable √ Rule 4: Valency of Cu is +2 and Ag is +1. NOT favorable

Expect Ag and Cu have limited solubility.

In fact, the Cu-Ag phase diagram (T vs. c) shows that a solubility of only 18% Ag can be achieved at high T in the Cu-rich alloys.

Hume-Rothery Empirical Rules In Action

r_solute − r_solvent

r_solvent x100%

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Cu-Ag Alloys Cu-Ni Alloys

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Ex) Application of amorphous alloy systems 1) Magnetic amorphous alloy (ribbon)

- transition metal-metalloid (TM-M) alloys rapid quenching - RE-TM alloys sputtering

- TM-Zr(Hf) alloys rapid quenching

role of metalloid element (ex. B) : lower melting point

Introduction_Amorphous

Introduction_Amorphous Materials Materials

2) Amorphous alloy as brazing filler (ribbon)

ex) Ni-based amorphous alloy

- for almost all metal without binder

Youngsmodulus, E (GPa)

Advanced Physical Metallurgy Advanced Physical Metallurgy

“ “ Amorphous Materials Amorphous Materials ” ”

Eun Eun Soo Soo Park Park

Office: 33-316

Telephone: 880-7221

Email: espark@snu.ac.kr

Office hours: by an appointment

2009 spring

03.04.2009

Contents for previous class Contents for previous class

• Amorphous Amorphous – from the Greek for “without form”

not to materials that have no shape,

but rather to materials with no particular structure

• grain boundaries

• no grain boundaries

Contents for previous class

Contents for previous class

Contents for previous class Contents for previous class

Contents for previous class Contents for previous class

Microstructure

Microstructure - - Properties Relationships Properties Relationships

Microstructure Properties

Processing

Performance

Design Design

“ “ Tailor Tailor - - made Materials Design made Materials Design ” ”

Contents for today

Contents for today ’ ’ s class s class

Introduction to Amorphous Materials

Glass Transition Temperature

History of Amorphous Metals

Glass Formation

Introduction to Amorphous Materials

Unique Properties of Amorphous Materials

Introduction_amorphous

Introduction_amorphous materials materials

Amorphous materials

a wide diversity of materials can be rendered amorphous

indeed almost all materials can.

- metal, ceramic, polymer

ex) amorphous metallic alloy (1960) - glassy/non-crystalline material

cf) amorphous vs glass

- random atomic structure (short range order) - rapid solidification from liquid state

- retain liquid structure

Glass:

Glass: undercooled undercooled liquid with high viscosity liquid with high viscosity

Effect of cooling rate on glass transition temperature

Effect of cooling rate on glass transition temperature

Introduction_amorphous

Introduction_amorphous metals metals

Thermodynamical aspect

Kinetic aspect

Structural aspect

Glass formation Glass formation Glass formation

Formation of crystalline phases

Retention of liquid phase

High glass-forming ability (GFA )

Suppression

High glass

High glass- -forming ability forming ability ( (GFA GFA )

)

Glass formation

Glass formation

History: amorphous metal History: amorphous metal

1934 Vapor deposition

1950 Electro-deposition: Ni-P alloy

: hard & corrosion resistant coating 1960 P. Duwez (Caltech)

- quenching: phases stable at high temperature

- quenching from liquid state

- eutectic system : α + β

Glass formation: stabilizing the liquid phase Glass formation: stabilizing the liquid phase

∑

Glass formation: stabilizing the liquid phase Glass formation: stabilizing the liquid phase

Bulk formation of metallic glass Bulk formation of metallic glass

Recent BMGs with critical size

Recent BMGs with critical size ≥ ≥ 10 mm 10 mm

Introduction_Amorphous

Introduction_Amorphous Materials Materials

Unique Properties:

Recent BMGs with critical size ≥ ≥ _{10 mm} _{10 mm}