The structural transformation caused by dislocation-induced heterogeneous nucleation in the fcc-to-bcc martensitic transformation in elastically anisotropic crystals was investigated by using a phase field micro-elasticity model. The 3-dimensional microstructure of the dislocation-induced martensitic embryos was obtained. It was found that the embryos were not single-domain particles as was usually assumed but instead a complex self-organized assembly of stress-accommodating twin-related micro-domains. Sessile metastable martensitic embryos around the dislocation loops formed in the prototype Fe-Ni alloy system above the temperature of the martensitic transformation. The possibility that the presence of these pre-existing embryos could be responsible for at least a fraction of the elastic modulus-softening with temperature-decrease, observed in many martensitic systems, was considered. The effects of elastic anisotropy, the so-called chemical-energy barrier and the structural anisotropy of the Landau free energy, upon the formation and growth of martensitic embryos were investigated. The assumptions of elastic isotropy and the choice of an anisotropic term in the Landau polynomial did not significantly affect the microstructure of martensitic embryos but could appreciably change the undercooling that was required in order to eliminate the total nucleation barrier and trigger the athermal martensitic transformation.

Modelling of Dislocation-Induced Martensitic Transformation in Anisotropic Crystals. W.Zhang, Y.M.Jin, A.G.Khachaturyan: Philosophical Magazine, 2007, 87[10], 1545-63