1 / 31

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

rod
Download Presentation

Interfaces

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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)

More Related