Bulk Metallic Glasses

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“Advanced Physical Metallurgy”

- Bulk Metallic Glasses -

Eun Soo Park

Office: 33-313

Telephone: 880-7221 Email: [email protected]

Office hours: by appointment

2014 Spring

03.06.2014

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Are amorphous metals useful?

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High fracture strength over 5 GPa in Fe-based BMGs

A.L. Greer, E. Ma, MRS Bulletin, 2007; 32: 612.

1. High strength of BMGs

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1. High strength of BMGs

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초경량화 및 초경박화에 적합

Zr계벌크 비정질 합금과 타 경량 합금의 경도와 비강도

Vickers hardness(Kg/mm2)

Mg 합금

Specific strength (σ(MPa)/ρ)

200

300 _AZ91

Al 380

Ti-Al6-4V

Al 합금 Ti 합금 Zr계

비정질합금 100

400 500 600 700

5 15 25 35 45

기존 상용 경량합금에 비하여 월등한 비강도로 재료의 획기적인 두께 감소가 가능

고비강도 및 고경도 (강도)

Mg – AZ91

More thin plate: ^{비정질 합금}

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Elastic Strain Limit

[ as % of Original Shape ]

Al alloy Ti alloy Stainless BMG

(Liquidmetal^®)

0.5 % 2.0 %

Strain, ε

2000 1500 1000 500

0

Stress σ (MPa)

Stainless steel

BMG

Stress-Strain Curve

2. Large elastic strain limit of BMGs

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2. Large elastic strain limit of BMGs

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: Metallic Glasses Offer a Unique Combination of High Strength and High Elastic Limit

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구조재료로서 비정질 합금의

Drawback

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0.0 0.5 1.0 1.5 2.0 2.5 3.0

Engineering Stress (GPa)

0 2 4 6 8 10 12 14 16

Engineering Strain (%)

Conventional metal - low strength

Amorphous metal

- limited plasticity (0~2%) - catastrophic failure

20㎛

200㎛

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Footprints in sand.

Water quickly disappears underneath

Elementary flow events in metallic glasses

Shear bands form by accumulation of defects during deformation.

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Ni₆₀Nb₄₀: fully amorphous phase

100 μm

S=0.016 mm/sec

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200 nm

~ 20 nm

clear boundary between undeformed matrix and shear bands

~ 20 nm

HRTEM image of a shear band Shear deformed areas with the same composition & different density of free volume

Shear bands form by accumulation of defects during deformation.

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High fracture toughness: > 10 % plastic strain in tensile test

Nature 451 (2008) 1085

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Douglas C. Hofmann, SCIENCE VOL 329 10 SEPTEMBER 2010

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Z.P. Lu, et al. Adv. Mater. 2010, 22, 2770–2773

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Reversible phase transformation behavior during cyclic tensile test _ ESPark group, SNU

Initial BCC phase in as-cast sample Deformed martensite phase

Loading → Unloading → Reloading

By Dr. Ryan Ott (AMES) at APS beam line Ti-Cu-Ni-X Ф3mm

Water cooled Cu mold suction casting,

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- 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

Magnetic cores

Transformers

0.1 1 10 100 1000 10000

Frequency , f [kHz]

1000 10000 100000 1000000

Permeability , [m]

Amorphous (Co- Based)

Permalloy (70 mm)

Nanocrystalline (VITROPERM)

Mn-Zn ferrite (Siferrit T38)

Low hysteresis loss

Frequency, f [kHz]

Permeability, [μ]

www.metglas.com

3. Old uses: soft magnet

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< 아몰퍼스변압기 사용연수 대비 에너지절감효과 >

(전기안전, 대우증권 리서치본부)

초기설치비는 기존 변압기에 비해 1.5배 정도 비쌈 그러나 손실절감효과를 반영하면 2.7년 후면 만회 변압기 사용 연수 약 10~15년 감안시 큰 효과

일반 규소강판 변압기 대비 대기 전력 75% 이상 절감

Amorphous metal magnetic core

사용년수

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1) Micro-casting

T_melting T_g

Molar Volume, V

Liquid

Glass formation:

continuous change

Crystal Glass

Temperature, T

Crystallization:

abrupt change

Near-net shape production

Cavity Die

Vacuum Chamber

Molten Alloy

Induction Coil

sleeve

Plunger

Die

Precision die casting

Precision Gears for Micro-motors

MRS BULLETIN 32 (2007)654.

4. Processing metals as efficiently as plastics

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2) Thermoplastic forming

400 500 600 700

Temperature (K)

Exothermic (1 w/g per div.)

T_g T_x

Amorphous Supercooled liquid Stable liquid

Crystalline T_s T_l ΔT_x

Tensile specimens following superplastic forming in supercooled liquid region

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3) Micro-forming

Micro-forming of three-dimensional microstructures from thin-film metallic glass Micro-cantilever Integrated conical spring linear actuator

Thickness: 5 μm 250 μm

50 μm

500 μm

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glass liquid

crystalline

T

Homogeneous Newtonian viscous flow

Metallic glass can be processed like plastics by homogeneous Newtonian viscous flow in supercooled liquid region (SCLR).

Possible to deform thin and uniform MG

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Nature 457, 868-872 (12 February 2009)

Ideal processing region

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Thermoplastic forming - Fabrication of nanowire

500 nm

Nakayama et al., Adv. Mat. 22 (2010) 872-875.

1 mm

100μm 100 μm

1μm

SEM image of nanometer scale metallic glass wire formed by drawing micrometer scale wire on hotplate

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상용 비정질 합금 LM1b (Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅) 의 TPF을 이용한 가압 성형

sample

Uniaxial pressing

Thermoplastic forming - Fabrication of BMG plate

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110mm

115mm

Joining을 통한 대면적화

기존의 bulk sample 제작 기술로 구현이 불가능했던 대면적/부피의 비정질 합금 제조 가능.

비정질 형성능의 제약 극복, 다양한 조성에서 제품 제작 가능.

Thermoplastic forming & joining - Fabrication of BMG plate

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PtNiCuP T = 270°C P = 10 Mpa 100 sec J. Schroers, JOM, 57, 34 (2005)

“비정질 형성능 제약 극복” Thermoplastic forming & Joining technique

최소 크기의 bulk 비정질 합금을 제조 할 수 있다면 조건에 따라 어떠한 크기로도 성형 가능, 복잡한 형상 을 HT pressing 만으로 단일 구조로 제작 가능.

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Unachievable shapes for metals?

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Jan Schroers, Adv. Mater., 2010, hologram pattern

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SURFACE REPLICATION WITH BMGs

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Metallic Glass Fuel Cell

Endplate Electrode, Catalyst

1 mm

R. C. Sekol, M. Carmo, G. Kumar, J. Schroers, and A. D. Taylor, Small 9, 2081 (2013)

5 mm

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Metallic glass electrode- A closer look

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우수한 고온 성형성 (Superplastic Forming)

: 복잡한 형태도 단일 구조로 제조, 접합부 없이 성형 가능 Seamaster Planet Ocean Liquidmetal® Limited Edition

고가의 소형 IT기기 제조에 적합

다단계의 공정을 casting단계 만으로 해결 가능

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2014-03-11

USIM ejector (iphone 4)

Apple is using Liquidmetal for…

Enclosure / Antenna

Apple buys exclusive right for Liquidmetal

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Medical Devices

Sporting Goods

Fine jewelry Drill pipe, container etc.

www.liquidmetal.com

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Ashby map

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)

Youngs modulus, E (GPa)

< Ashby map >

0.1 1 10 100 1000 10000

0.01 0.1

1 10 100 1000

Metallic glasses

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www.liquidmetal.com

Menu of engineering materials

composite Metals

Polymers

Ceramics

Metallic Glasses

Elastomers

High GFA

High plasticity

higher strength

lower Young’s modulus high hardness

high corrosion resistance good deformability

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By eliminating or reducing the effectiveness of

heterogeneous nucleation sites, it should be possible to form bulk metallic glasses

with virtually unlimited dimensions.

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