Microstructure Evolution Interfaces Microstructure ByeongJoo Lee POSTECH MSE

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

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

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

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

Estimation of Solid Surface Energy - Origin of Surface Energy Pair approximation Necessary Work for Creation of (111) surface in fcc (/atom) For fcc (111): N/A = 4/(31/2 a 2) fcc (100): N/A = 2/a 2 For Cu: a = 3. 615 Å △Hs =337. 7 J/mol γ(111) = 2460 erg/cm 2 (1700 by expt. ) For fcc ※ Origin of Anisotropy Byeong-Joo Lee cmse. postech. ac. kr

Estimation of Solid Surface Energy - Orientation dependence High Index Surface Energy Comparisons 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). Byeong-Joo Lee cmse. postech. ac. kr

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

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

An issue for thinking - Surface Transition and Alloying Effect Pure W W + 0. 4 wt% Ni Vaccum Annealing 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 Byeong-Joo Lee cmse. postech. ac. kr

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

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

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

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

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

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

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

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

Normal Grain Growth - the mechanism 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 2 r ⇒ drive it ! • • total dragging force per unit area Maximum grain size Byeong-Joo Lee cmse. postech. ac. kr

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

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

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

Grain Boundary Energy of BCC Fe H. -K. Kim et al. , Scripta Mater. (2011) Sigma (Σ) 5 3 11 9 3 7 3 9 7 5 3 5 11 7 9 5 Theta (θ) 36. 87 70. 53 50. 48 38. 94 60 38. 21 131. 81 96. 38 73. 4 180 101. 54 62. 96 135. 58 90 143. 13 (hkl) plane 100 110 111 111 210 210 211 211 221 Sigma (Σ) 11 5 7 3 9 11 5 11 7 7 9 9 11 7 5 11 Theta (θ) 144. 9 180 115. 38 146. 44 67. 11 180 95. 74 100. 48 149 180 123. 75 152. 73 82. 16 110. 92 154. 16 180 (hkl) plane 310 310 311 311 320 321 322 331 331 332 Byeong-Joo Lee cmse. postech. ac. kr

Phase field simulation of grain growth - Isotropic GBE H. -K. Kim et al. (2013) - Anisotropic GBE (realistic GBE DB) - Isotropic GB mobility - Random crystallographic orientation vs. weakly-textured orientation (LAGB = 1. 4 % vs. 4. 9 %) Byeong-Joo Lee cmse. postech. ac. kr

Phase Field Simulation of γ→α transformation in steels Wetting angle : 36 o Wetting angle : 120 o Fe - 0. 5% Mn – 0. 1% C, d. T/dt = 1 o. C/s from SG Kim, Kunsan University Byeong-Joo Lee cmse. postech. ac. kr

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

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

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

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

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