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

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Presentation transcript:

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

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

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 For Cu: a = 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

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

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 Pure W W + 0.4wt% Ni Vaccum Annealing An issue for thinking - Surface Transition and Alloying Effect

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 Grain Boundaries

Byeong-Joo Lee cmse.postech.ac.kr Grain boundaries in Solids - Misorientation Misorientationvs.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 4 o 7 o 3 o 4 o 7 o 10 o 15 o 20 o 30 o o 20 o 30 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 · 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

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 2r ⇒ 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 How to uniquely define misorientation and inclination between two neighboring grains H.-K. Kim et al., Scripta Mater. (2011)

Byeong-Joo Lee cmse.postech.ac.kr Sigma (Σ)Theta (θ)(hkl) planeSigma (Σ)Theta (θ)(hkl) plane Grain Boundary Energy of BCC Fe H.-K. Kim et al., Scripta Mater. (2011)

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)

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

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

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

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

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

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

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