Plasticity of Two-Phase Materials with a Coarse Microstructure.

The combined effect of hard and soft components on the plastic deformation of coarse two-phase materials is reviewed with reference to experimental data for steels and aluminum bronzes and to theoretical models. The presence of a hard component affects mainly the rate of strain hardening at small strains. The deformation process can be described by an empirical ″mixture rule″ which distributes both stresses and strains in the ratio of the volume fractions of the phases; the resulting excess of strain in the soft phase (and of stress in the hard phase) increases with the ratio of the flow stresses of the phases, and decreases with the volume fraction of hard phase. Load transfer between phases is shown to play the dominant role in the strengthening of these materials; the contribution of geometrically necessary dislocations is comparatively minor. The deformation of the phases and of the whole aggregate can be modeled satisfactorily by two-dimensional finite element method calculations based on two-dimensional structure models.