COMPUTATIONAL MODELING OF METAL-MATRIX COMPOSITE-MATERIALS .4. THERMAL DEFORMATIONS

The mechanical behavior of particulate reinforced metal matrix composites, in particular an SiC reinforced Al-3 wt% Cu model system, was analyzed numerically using the computational micromechanics approach. In this, the fourth and final article in a series, the microscale effects of thermo-mechanical processing is investigated in detail. Two ideal processes are considered. The first represents a simple quench and the second combines a high temperature compression, to simulate rolling or extrusion, with a quench. These processes, through applied deformation and thermal expansion mismatch, produce inhomogeneous, and localized, stress and plastic strain fields in the composite microstructures. The structure of these residual fields can be related to reinforcement volume fraction and microstructural morphology. For the simple quench, volume average plastic strains are almost proportional to reinforcement volume fraction and there is a negligible morphological dependence. Large magnitude residual stress and strain fields, as well as large geometry changes, result from the second process. The effects of these processes on subsequent deformation behavior of composites for a selection of morphologies is investigated. Apart from almost doubling yield strains, the simple quench has relatively minor microscale and macroscale effects. The second process has a considerable effect on yield strength and introduces differences between tensile and compressive behavior on both the macroscale and microscale. Plastic constraint is an important mechanism. The physical relevance of these particular processing simulations, and the implications for modeling of microscale failure are discussed.