| Abstract Scope |
While in Sweden, the author learned nonequilibrium thermodynamics from Hillert. The key concept is the separation of internal and external variables of a system. In equilibrium thermodynamics by Gibbs, the internal variables are not independent and can be evaluated from given external variables. While irreversible thermodynamics led by Onsager focused on internal variables. Hillert integrated them together by first emphasizing their differences and then examining their connections. His philosophy was reflected by his book “Phase Equilibria, Phase Diagrams and Phase Transformations” that puts equilibrium, nonequilibrium, and internal processes on equal footing, which was what the CALPHAD modeling pioneered by Kaufman was based on. In this presentation, both Gibbs and Hillert thermodynamics will be discussed. The central concept of lattice stability in CALPHAD thermodynamic modeling reflects an important internal variable in Hillert thermodynamics. As one of the key practitioners of CALPHAD modeling, Rainer Schmid-Fetzer has made significant contributions. |