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Interfaces

Phase Transformations. Interfaces. Byeong-Joo Lee POSTECH-MSE. Scope. Fundamentals 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

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Interfaces

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  1. Phase Transformations Interfaces Byeong-Joo LeePOSTECH-MSE

  2. Scope • Fundamentals • 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

  3. Question Origin of Surface Energy ?

  4. Rough Estimation of Solid Surface Energy Pair approximation Necessary Work for Creation of (111) surface in fcc (/atom) For fcc (111): N/A = 4/(31/2a2) fcc (100): N/A = 2/a2 For Cu: a = 3.615 Å △Hs =337.7J/mol γ(111) = 2460 erg/cm2 (1700 by expt.) For fcc ※ Origin of Anisotropy

  5. Rough Estimation of Surface Energy J. Park, J. Lee, Computer Coupling of Phase Diagrams and Thermochemistry 32 (2008) 135–141

  6. Equlibrium shape of a Crystal

  7. Atomistic Computation of Surface Energy Grain Boundary / Interface

  8. Atomistic Computation of Surface Energy Grain Boundary / Interface

  9. Question Grain Boundary / Interface

  10. Interfaces in Solids – Coherent Interfaces • twin boundary • phase boundary with the same structure and orientation               •  ⇒ concentration gradient energy ∝ [ΔX]2 • 3. coherent interfaces with strain • ※ Equilibrium Shape from Y.S. Yoo

  11. 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

  12. Morphological Evolution - from Y.S. Yoo, KIMS

  13. Morphological Evolution - from Y.S. Yoo, KIMS

  14. Interfaces in Solids – Semi-Coherent Interfaces Disregistry Misorientation twist boundary

  15. [100] Twist Boundary Structure in pure Cu – Misorientation Dependency 3o 4o 7o 10o 15o 20o 30o 45o

  16. [100] Twist Grain Boundary Energy of Copper

  17. Interfaces in Solids – Incoherent Interfaces · Incoherent boundary energy is insensitive to orientation.       ※ Special boundaries with low energy [100] and [110] tilt Boundary energy of Al

  18. More about Surface/Interface Energy – High Index Surfaces 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).

  19. Calculation of Grain Boundary Energy– B.-J. Lee, MSMSE, 2004

  20. Measurement of Surface Energy – Relative Interface Energy of Solid θ

  21. Question Interfacial Phenomena (Interface or Surface Segregation) • Thermodynamics of Surface or Grain Boundary Segregation • M. Guttmann, Surf. Sci., 53 (1975) 213-227; Metall. Trans. A, 8A (1977) 1383-1401. • T. Tanaka and T. Iida, Steel Research, 65, 21-28 (1994).

  22. Interfacial Phenomena – Segregation (Guttmann) Assume a one atomic layer surface phase and consider equilibrium between bulk and surface where ωi is the molar surface area Assume ωi = ωj = … = ω

  23. Interfacial Phenomena – Segregation (Physical Meaning of Quantities)

  24. Interfacial Phenomena – Segregation (Butler/Tanaka)

  25. Thermodynamic Calculation of Surface Tension of Liquid Alloys on the Web-board of this Lecture

  26. Thermodynamic Calculation of Surface Segregation in Solid Alloys

  27. Key Point Surface/Interface Energy of Crystalline Solids is Anisotropic

  28. Surface Transition and Alloying Effect – N.M. Hwang et al., 2000. W + 0.4wt% Ni Pure W Vaccum Annealing

  29. Abnormal Grain Growth – from N.M. Hwang

  30. Abnormal Grain Growth – from N.M. Hwang

  31. Interfacial Phenomena – Abnormal Grain Growth (N.M. Hwang)

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