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Byeong-Joo Lee cmse.postech.ac.kr Byeong-Joo Lee POSTECH - MSE Interfaces & Microstructure.

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Presentation on theme: "Byeong-Joo Lee cmse.postech.ac.kr Byeong-Joo Lee POSTECH - MSE Interfaces & Microstructure."— Presentation transcript:

1 Byeong-Joo Lee cmse.postech.ac.kr Byeong-Joo Lee POSTECH - MSE calphad@postech.ac.kr Interfaces & Microstructure

2 Byeong-Joo Lee cmse.postech.ac.kr Scope Fundamentals 1.Free Surfaces vs. Grain Boundaries vs. Interphase Interfaces 2.Concept of Surface Energy/Surface Tension 3.Origin of Surface Energy and its Anisotropy 4.Grain Boundary/Interfacial Energy Interface Phenomena 1. Curvature Effect 2. Multi-component system Segregation 3. General Grain Growth Morphological Evolution

3 Byeong-Joo Lee cmse.postech.ac.kr Surfaces

4 Byeong-Joo Lee cmse.postech.ac.kr Concept of Surface Energy and Surface Tension for liquid film Generally,

5 Byeong-Joo Lee cmse.postech.ac.kr For Cu: a = 3.615 Å △ Hs =337.7J/mol γ (111) = 2460 erg/cm 2 (1700 by expt.) For fcc ※ Origin of Anisotropy Pair approximation Necessary Work for Creation of (111) surface in fcc (/atom) For fcc (111): N/A = 4/(3 1/2 a 2 ) fcc (100): N/A = 2/a 2 Estimation of Solid Surface Energy - Origin of Surface Energy

6 Byeong-Joo Lee cmse.postech.ac.kr Comparisons High Index Surface Energy 1. W.R. Tyson and W.A. Miller, Surf. Sci. 62, 267 (1977). 2. L.Z. Mezey and J. Giber, Jpn. J. Appl. Phys., Part 1 21, 1569 (1982). Estimation of Solid Surface Energy - Orientation dependence

7 Byeong-Joo Lee cmse.postech.ac.kr Equilibrium shape of a Crystal - Wulff construction

8 Byeong-Joo Lee cmse.postech.ac.kr Equilibrium shape of a Crystal - Numerical Example

9 Byeong-Joo Lee cmse.postech.ac.kr Pure W W + 0.4wt% Ni Vaccum Annealing An issue for thinking - Surface Transition and Alloying Effect

10 Byeong-Joo Lee cmse.postech.ac.kr Note - Estimation of Surface Energy J. Park, J. Lee, Computer Coupling of Phase Diagrams and Thermochemistry 32 (2008) 135–141

11 Byeong-Joo Lee cmse.postech.ac.kr Grain Boundaries Grain Boundaries

12 Byeong-Joo Lee cmse.postech.ac.kr Grain boundaries in Solids - Misorientation Misorientationvs.Inclination

13 Byeong-Joo Lee cmse.postech.ac.kr Grain boundaries in Solids - tilt vs. twist boundaries

14 Byeong-Joo Lee cmse.postech.ac.kr [100] Twist Boundary Structure in pure Cu 3 o 4 o 7 o 3 o 4 o 7 o 10 o 15 o 20 o 30 o 45 15 o 20 o 30 o 45 o

15 Byeong-Joo Lee cmse.postech.ac.kr [100] Twist Grain Boundary Energy of Copper

16 Byeong-Joo Lee cmse.postech.ac.kr Special High-Angle Grain Boundaries

17 Byeong-Joo Lee cmse.postech.ac.kr · Incoherent boundary energy is insensitive to orientation. ※ Special boundaries with low energy [100] and [110] tilt Boundary energy of Al Special High-Angle Grain Boundaries

18 Byeong-Joo Lee cmse.postech.ac.kr Equilibrium Microstructure - balance of GB tensions θ

19 Byeong-Joo Lee cmse.postech.ac.kr Normal Grain Growth - the mechanism

20 Byeong-Joo Lee cmse.postech.ac.kr Effect of particles on Grain Growth - Zener pinning effect Consider the balance between the dragging force (per unit area) and the pressure from the curvature effect dragging force due to one particle of size r number of ptl. per unit area of thickness 2r ⇒ drive it ! total dragging force per unit area Maximum grain size

21 Byeong-Joo Lee cmse.postech.ac.kr Abnormal Grain Growth – Mechanism ?

22 Byeong-Joo Lee cmse.postech.ac.kr Effect of Anisotropic GBE and Precipitates on Abnormal GG C.-S. Park et al., Scripta Mater. (2012)

23 Byeong-Joo Lee cmse.postech.ac.kr Grain Boundary Identification Scheme How to uniquely define misorientation and inclination between two neighboring grains H.-K. Kim et al., Scripta Mater. (2011)

24 Byeong-Joo Lee cmse.postech.ac.kr Sigma (Σ)Theta (θ)(hkl) planeSigma (Σ)Theta (θ)(hkl) plane 536.8710011144.9310 370.531105180310 1150.481107115.38310 938.941103146.44311 360111967.11311 738.2111111180311 3131.81210595.74311 996.3821011100.48320 773.42107149320 51802107180321 31802119123.75321 5101.542119152.73322 1162.962111182.16331 7135.582117110.92331 9902215154.16331 5143.1322111180332 Grain Boundary Energy of BCC Fe H.-K. Kim et al., Scripta Mater. (2011)

25 Byeong-Joo Lee cmse.postech.ac.kr Phase field simulation of grain growth - Isotropic GB mobility - Random crystallographic orientation vs. weakly-textured orientation (LAGB = 1.4 % vs. 4.9 %) - Isotropic GBE - Anisotropic GBE (realistic GBE DB) H.-K. Kim et al. (2013)

26 Byeong-Joo Lee cmse.postech.ac.kr Wetting angle : 36 o Wetting angle : 120 o Fe - 0.5% Mn – 0.1% C, dT/dt = 1 o C/s from SG Kim, Kunsan University Phase Field Simulation of γ→α transformation in steels

27 Byeong-Joo Lee cmse.postech.ac.kr Interphase Interfaces Interphase Interfaces

28 Byeong-Joo Lee cmse.postech.ac.kr Interfaces in Solids – Coherent, Semi-Coherent & Incoherent Interfaces

29 Byeong-Joo Lee cmse.postech.ac.kr from Y.S. Yoo KIMS Interfaces in Solids – Shape of Coherent Second-Phase ※ Equilibrium Shape

30 Byeong-Joo Lee cmse.postech.ac.kr γ’ precipitates of Ni-Al alloy system, D.Y. Yoon et al. Metals and Materials Strain Energy vs. Interfacial Energy - Mechanism of particle splitting Phase Field Method Simulation by P.R. Cha, KMU

31 Byeong-Joo Lee cmse.postech.ac.kr Morphological Evolution - from Y.S. Yoo, KIMS

32 Byeong-Joo Lee cmse.postech.ac.kr Morphological Evolution - from Y.S. Yoo, KIMS

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