DEFORMATION OF 2-PHASE MATERIALS - A MODEL BASED ON STRAIN COMPATIBILITY

A model is proposed which describes the deformation behaviour of two-phase materials. It is based on a sandwich structure but is found to hold, in good approximation, for particle composites with moderate amounts of soft phase as well. The model emphasizes the mutual deformation constraint between the phases, which originates from the triaxiality of the stress state in soft phase regions close to hard phase boundaries, as long as the boundaries are to remain intact. The stress triaxiality (or the hydrostatic stress component connected with it) causes a "harder" response of the soft phase, and a "softer" response of the hard phase. Elastic properties can be expressed analytically, and the flow behaviour in the elastic-plastic regime can be calculated by an iterative procedure, yielding data on stresses, stress triaxiality, and strains in the soft and in the hard phase. Good agreement with experiment is obtained for two-phase microstructures consisting of WC and Co and of martensite and austenite.