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

The mechanical behavior of particulate reinforced metal matrix composi tes, in particular an SiC reinforced Al-3 wt% Cu model system, was ana lyzed 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 o r extrusion, with a quench. These processes, through applied deformati on and thermal expansion mismatch, produce inhomogeneous, and localize d, 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 reinforcem ent 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 sele ction of morphologies is investigated. Apart from almost doubling yiel d strains, the simple quench has relatively minor microscale and macro scale effects. The second process has a considerable effect on yield s trength and introduces differences between tensile and compressive beh avior on both the macroscale and microscale. Plastic constraint is an important mechanism. The physical relevance of these particular proces sing simulations, and the implications for modeling of microscale fail ure are discussed.