Dispersed-phase martensitic transformation controlled deformation behavior of two-phase metallic materials

A constitutive model which describes transformation plasticity accompanying stress-assisted martensitic transformation in two-phase material systems consisting of a stable matrix and a transforming dispersed phase is developed. The model consists of two parts: (a) a transformation thermodynamics/kinetics law describing the evolution of the transformed fraction of dispersed particles and (b) a constitutive law describing plastic flow resistance of the evolving three-phase (matrix phase, dispersed parent phase, dispersed product phase) composite material. The model is constructed in such a way that it can be readily implemented in a finite element program suitable for the analysis of boundary value problems. The model is used to analyze the uniaxial tensile behavior of the two-phase gamma Ti-Al matrix/beta (Ti-Al-V-Fe) phase system in order to rationalize an experimentally observed nearly 100% increase in tensile ductility of the material due to the martensitic transformation in the beta phase. The model is also used to study the uniaxial tensile behavior of beta/alpha two phase Ti-10V-2Fe-3Al (wt.%) alloy characterized by a sigmoidal stress-strain curve. A reasonably good agreement is obtained between the model predictions and the experimental data. (C) 1997 Elsevier Science Ltd.