Three-dimensional phase field model of low-symmetry martensitic transformation in polycrystal: Simulation of zeta '(2) martensite in AuCd alloys

A three-dimensional phase field model of the martensitic transformation tha t produces a low symmetry phase in polycrystals is developed. The transform ation-induced strain mostly responsible for the specific features of the ma rtensitic transformation is explicitly taken into account. The high computa tional efficiency of the model turns out to be almost independent of the co mplexity of the polycrystal geometry. An example of the cubic --> trigonal transformation in AuCd alloys producing zeta'(2) martensite is considered. The development of the transformation through nucleation, growth and coarse ning of orientation variants is simulated for both single crystal and polyc rystalline materials. The effect of an external load on the martensitic mic rostructure in the polycrystalline material is studied. It is shown that th e elastic coupling between different transformed grains of the polycrystal drastically affects the microstructure and its response to the applied stre ss. The obtained self-accommodating morphologies of the multivariant marten sitic structure are in agreement with those observed in the experiments. (C ) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights r eserved.