The transformation sequences in the cubic - tetragonal decomposition

摘要

The decomposition of a generic supersaturated binary cubic solid solution into a mixture of cubic and tetragonal phases is investigated by phase field microelasticity modeling and simulations. It is shown that the decomposition in such a system is not necessarily developed by conventional nucleation and growth of the tetragonal phase. There are three temperature and composition ranges where the sequences of transient structures formed are different. The transformation pathways are predicted and the corresponding thermodynamic parameters are identified. In particular, the simulations reveal unusual transformation sequences occurring in the process of iso-structural decomposition followed by cubic tetragonal MT confined within one of the decomposed cubic phases. Mechanisms for the formation of the stress-accommodating multi-domain aggregates of the tetragonal phase and the checkerboard-like structures comprised of parallel rods of cubic and tetragonal phases are discussed. Published by Elsevier Ltd on behalf of Acta Materialia Inc.