Dynamic theory of morphological characteristics of crystals of ε and γ phases, including Headley–Brooks orientation relationships upon the α–ε and α–ε–γ martensitic transformations

Abstract

Different variants of the formation of martensite crystals upon the α–γ transformation caused by the tension–compression deformation of {110}α planes have been considered according to the dynamic theory of martensitic transformations. In contrast to previous works, here we take into account the deviation (angle θ) of the principal directions of deformation from the symmetry axes (Formula Presented.). It has been shown that the requirement of the symmetry of the arrangement of atoms in the basal plane {0001}ε is satisfied in the range of angular deviations–(Formula Presented.). The algorithm for calculating the morphological characteristics is illustrated based on the example of an elastically isotropic medium, which does not require assigning concrete values of elastic moduli. The estimations performed make it possible, in particular, to explain the physical nature of the Headley–Brooks orientation relationships as a result of the inheritance of one of the variants of permissible material orientation relationships for the α–ε transformation in the course of the ε–γ transformation at θ ~ 35°. The changes in the other morphological signs are also discussed. © 2015, Pleiades Publishing, Ltd.