Theoretical calculation of the stress-strain behavior of dual-phase metals with randomly oriented spheroidal inclusions

Abstract

A simple model is developed to determine the overall response of dual-phase metals with an inclusion/matrix microgeometry. The inclusions are taken to be spheroidal in shape and are randomly oriented and homogeneously dispersed in the matrix. No restriction is placed on whether the inclusions are harder or softer (in the sense of flow stress) than the matrix, and as with most dual-phase metals, both phases are capable of undergoing plastic flow. The yielding process of the inclusions is now orientation dependent and sequential, and the overall elastoplastic response of the two-phase system is found to be strongly dependent upon the inclusion shape and concentration, even more so than on the corresponding elastic behavior. Disc-shaped inclusions generally give a superior reinforcing effect when the matrix is the softer phase, whereas spherical inclusions are more effective when the matrix is the harder one. As compared to the condition when the inclusions are strictly elastic, the plasticity of inclusions is found to translate into noticeable reduction in the flow stress of the composite. Comparison of the theoretical prediction with the experimental data for a ferrite/austenite system further shows a reasonable agreement.