Effect of cyclic plasticity on internal stresses in a metal matrix composite

Neutron diffraction has been used to measure the elastic strains in a silicon carbide particle-reinforced aluminum alloy during cyclic plasticity. Strains were recorded in both phases of the material, in sufficient directions to allow for calculation of the internal stresses. The shape misfit stress in the composite was calculated from the macroscopic stress data using an Eshelby-based model. Changes in the misfit stress caused by plastic deformation can be clearly observed. Local plastic anisotropy of the matrix material is also seen and was monitored by comparing results from the two diffraction planes, {111} and {200}, that were measured. The results have been compared to those obtained using an elasto-plastic self-consistent modeling approach, which shows the evolution of load sharing between the matrix and reinforcement, as well as the origin of the plastic anisotropy strains in the aluminum.