Phase Stability, Diffusion, Kinetics and their Applications (PSDK-VI): Session Honoring John W. Cahn, Recipient of ASM's 2011 J. Williard Gibbs Phase Equilibria Award
Program Organizers: Jeffrey LaCombe, University of Nevada, Reno; Yongho Sohn, University of Central Florida; John Morral, The Ohio State University; Ursula Kattner, National Institute of Standards and Technology; Abhijeet Misra, QuesTek Innovations LLC
Tuesday 8:00 AM
October 18, 2011
Room: C214
Location: Greater Columbus Convention Center
Session Chair: Ursula Kattner, National Institute of Standards and Technology; John Morral, The Ohio State University
8:00 AM
Gibbs Lost, Found, Applied and Supplemented (Dedicated to the Memory of Francis Larché): John Cahn1; 1NIST and University of Washington
In 1876-8 in 300 pages Gibbs created complete thermodynamics of heterogeneous phase equilibrium. This gem still needs to be studied. Gibbs is more rigorous and often simpler about some concepts than what is currently taught. Leaving ideas to be supplemented and fully developed, Gibbs created career opportunities. The phase rule occupied just one page; he took more space to create a phase rule for liquid-gas critical phases, but could not have known about solid order-disorder criticality. The thermodynamics of solid and fluid surfaces was fully developed, but he left that of recently discovered grain boundaries to the reader. Many materials concepts were unknown in Gibbs’ time. Solids were limited to stoichiometrical compositions; chemical potentials of separate components could not be defined, and solid diffusion was thought impossible. New concepts arising about nature of matter continue to create opportunities for us to do what Gibbs might have done.
8:40 AM Question and Answer Period
9:20 AM Break
9:40 AM
Thermodynamics of Interfaces: From Willard Gibbs to John Cahn to Recent Developments: Y. Mishin1; 1George Mason University
This talk will attempt to summarize John Cahn’s seminal contributions to the field of interface thermodynamics and their relation to the classical theory developed by J. Willard Gibbs. The discussion will include the diffuse interface theory, the critical wetting analysis, the capillarity vector concept, the method of generalized interface excesses, the reformulation of interface stress, and many important contributions to nucleation theory, including nucleation on dislocations. A few topics will be covered in more detail, such as the formalism of generalized excesses and heterogeneous nucleation theory. Recent progress in some of these areas will be briefly discussed, including thermodynamics of solid-fluid and solid-solid interfaces under applied stresses, interface melting and premelting, and heterogeneous nucleation beyond the classical theory.
10:20 AM
Surface Stress: A Materials Science Perspective: Jörg Weissmüller1; 1Technische Universität Hamburg-Harburg and Helmholtz-Zentrum Geesthacht
The phenomenon of surface stress has long led a wallflower existence in the materials sciences. Surface science has focused on the forces originating from planar single crystal surfaces, and mechanics provides local balance equations for stress at a curved segment of surface. Yet, investigating capillary forces acting on real materials surfaces with a complex geometry brings many challenges. What is more, it is often felt that surface stress simply does not matter in conventional materials. The modern focus on things nano changes the game. When the size of an object or the characteristic length-scale of its microstructure are small, the capillary forces at the interfaces do significantly affect the behaviour. This applies equally to such diverse issues as phase equilibrium, strength, (apparent) electrostriction, sensing and catalytic performance. The talk advertises recent experiments in that context and discusses how they connect to the findings in surface science and mechanics.
11:00 AM
Coherent Precipitation in Ternary Al Alloys: Insights from First-Principles Modeling: Colin Ophus1; Maarten de Jong2; Mark Asta2; Ulrich Dahmen1; Velimir Radmilovic1; 1Lawrence Berkeley National Laboratory; 2University of California, Berkeley
This talk will discuss recent insights, derived from the combination of first-principles total energy calculations and statistical-thermodynamic modeling, related to coherent precipitation phenomena in ternary Al-based alloy systems. The studies have been motivated by observations obtained from advanced electron-microscopy and atom-probe-tomography studies in Al-Si-Ge and Al-Sc-Li. In the former system, it is observed that the precipitation of stable diamond-cubic precipitates are preceded by coherent precipitation of nano-scale coherent precipitates that have a mixed Si-Ge content. The results are analyzed in the framework of a first-principles statistical-thermodynamics treatment that explicitly accounts for elastically-mediated interactions within the framework of a Kanazaki-force formalism. We further discuss results obtained by combining first-principles-based thermodynamics methods with mean-field models for diffusion-limited precipitate growth in the Al-Sc-Li system. The results explain that the observed, highly monodisperse size distributions for core-shell precipitates in this system arise from capillary effects that can be readily exploited in designing heat treatments.