A simple model for the prediction of coherent and semicoherent plate precipitate habit planes

Abstract

A quantitative physical description of the processes that determine plate precipitate habit planes evolves when a transformation with strains of mixed sign is modelled as a tensile test. The state of stress in such a thin coherent plate is similar to that in a tensile bar. The tensile axis, and with it the habit plane, is determined by the elastic anisotropy in the coherent case and by the slip geometry in the semicoherent case. The physical connection between the habit planes predicted by the anisotropic strain energy minimum criterion and the invariant plane strain criterion of martensite theory lies in the different constraints imposed by elastic or plastic yielding. Examples of the application of the principles and comparisons with experimental observations are given.