HEAT-TREATMENTS IN ALUMINUM-LITHIUM COMPOSITES EXTRUSION

Aluminium-matrix composites have attracted considerable academic and i ndustrial attention in recent years where modulus increases of 100% an d strength increases of 60% have been reported. The addition of lithiu m further enhances most of these properties through the precipitation of the coherent phase, delta'. Their widespread usage is limited by th e low room temperature ductility, although there remains scope for sup erplasticity and hence high temperature studies of this new class of m aterial. In this work, the high temperature age hardening behaviour of a silicon carbide particulate-reinforced aluminium-lithium alloy is p resented and compared with that of a similarly thermomechanically trea ted matrix material. Differential Scanning Calorimetry results are als o presented. Peak hardness and times are shown to be a function of bot h ageing temperature and material. Differences in peak hardness and ti mes should be taken into consideration when developing a generalised m odel for the deformation behaviour of discontinuously reinforced metal -matrix composites.