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B. B. Rath Symposium Thermodynamics of Interfaces in Mechanically Alloyed Metals

This symposium focuses on the thermodynamics of interfaces in mechanically alloyed metals, including mechanically alloyed oxide dispersion strengthened metals. The atom probe image of MA957 and MA956, as well as the mechanical mixture free energy of mechanical O.M Mixture, will be discussed. The Gibbs free energy per mole, composition, entropy, and solution-like behavior of particles will also be explored.

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B. B. Rath Symposium Thermodynamics of Interfaces in Mechanically Alloyed Metals

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  1. B. B. Rath SymposiumThermodynamics of Interfaces inMechanically Alloyed Metals

  2. Mechanically Alloyed Oxide Dispersion Strengthened Metals

  3. Atom probe image of MA957

  4. MA956 Chou & Bhadeshia, 1994

  5. MA956 Chou & Bhadeshia, 1994

  6. Mechanical Mixture free energy of mechanical o m mixture B G* o m Gibbs free energy per mole A x 1-x A B Concentration x of B

  7. free energy of mechanical o m mixture B G* Gibbs free energy per mole o m A ∆G M G{x} free energy of solution A B x Composition

  8. Entropy P P / 2

  9. + =

  10. For a random mixture, number of configurations given by:

  11. Boltzmann

  12. Badmos and Bhadeshia, 1997

  13. Classical theory for entropy of mixing

  14. Solution-like behaviour when particles about 1000 atoms in size Free energy of mixing due to configurational entropy alone

  15. Enthalpy

  16. Surface per unit volume Sv Solution formation impossible! Particle size

  17. coherent coherent incoherent

  18. Single barrier to solution formation when components attract Badmos and Bhadeshia, 1997

  19. Double barrier to solution formation when components immiscible Badmos and Bhadeshia, 1997

  20. o m B o m A Gibbs free energy per mole A B Paradox at concentration extremities vanishes in the discrete model of concentration Concentration x of B

  21. Amorphous phase formation during mechanical alloying of Cu and Cd powders ….contribution from Cu/d interfaces, and accompanying increase in free energy, provide additional driving force for amorphisation…. Zhang & Massalski Metall. & Mater. Trans. 29A (1998) 2425

  22. MA957, 1330 - 30 °C Capdevila & Bhadeshia, 2000

  23. Normal Grain Size Sub Micron Grain Size Grain junctions powerful pinning points for small grains, which are no longer topologically independent

  24. Evolution of SolutionsThermodynamics of Mechanical Alloying A. Badmos and H. K. D. H. Bhadeshia, Metall. & Mater. Trans. A, 18A (1997) 2189. H. K. D. H. Bhadeshia, Proceedings of the Royal Microscopical Society, 35 (2000) 95. Materials Science and Technology, 16 (2000) 1404. H. K. D. H. Bhadeshia & H. Harada, Applied Surface Science, 67 (1993) 328.

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