Heat treatments in aluminium-lithium composites extrusion

Aluminium-matrix composites have attracted considerable academic and industrial attention in recent years where modulus increases of 100% and strength increases of 60% have been reported. The addition of lithium further enhances most of these properties through the precipition of the coherent phase, δ′. Their widespread usage is limited by the low room temperature ductility, although there remains scope for superplasticity and hence high temperature studies of this new class of material. In this work, the high temperature age hardening behaviour of a silicon carbide particulate-reinforced aluminium-lithium alloy is presented and compared with that of a similarly thermomechanically treated matrix material. Differential Scanning Calorimetry results are also presented. Peak hardness and times are shown to be a function of both ageing temperature and material. Differences in peak hardness and times should be taken into consideration when developing a generalised model for the deformation behaviour of discontinuously reinforced metal-matrix composites.