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Center for Nonlinear Studies |
It is gradually getting clear that the macroscopic description of microstructure evolution requires additional thermodynamic parameters, entropy of microstructure and temperature of microstructure. It was claimed that there is "one more law of thermodynamics": entropy of microstructure must decay in isolated thermodynamically stable systems. Such behavior is opposite to that of thermodynamic entropy. This talk aims to illustrate the concept of microstructure entropy by several physical examples. The most non-elementary one is the grain growth in polycrystals. The grain growth will be treated within the framework of a theory, which is a modification of Hillert theory. The modification is made in order to reach simultaneously two goals: to get a coincidence of theoretical predictions with experimentally observed results and to obtain the equations that admit analytical solutions. Due to these features, the modified theory is of independent interest. In the modified Hillert theory one observes the decay of total microstructure entropy when the system approaches the self-similar regime. The microstructure entropy per one grain grows indicating a chaotization of grain sizes. It is essential that the grain boundary microstructure possesses an equation of state: there exits an equation that links entropy of microstructure, energy of microstructure, average grain size and a characteristic of the grain size scatter for the largest grains; this equation holds for evolution of every grain boundary microstructure. The talk will include a review of thermodynamic laws from perspectives of dynamic system theory.
Host: Turab Lookman, T-4, txl@lanl.gov, 665-0419