Abstract
Pure aluminium matrix composites reinforced mainly with a fine needlelike Al3Zr phase were synthesised by the reaction between nanocrystalline ZrO2 particles and pure aluminium using powder metallurgy followed by hot extrusion and hot rolling. After extrusion, the composite fabricated with 5 vol.-%ZrO2 had a strain rate sensitivity (m value) of 0.31 and a total elongation of 156% at 650°C and 1.3×10-1 s-1. The high strain rate superplasticity was improved by hot rolling. After hot rolling, the m value of the composite fabricated with 10%ZrO2 particles was 0.40 and the total elongation was 204% at 640°C and 1.3×10-1 s-1. The superplastic deformation mechanism for the present composites involves grain boundary sliding and interfacial sliding. From this mechanism, the following experimental results can be easily understood: the total elongation increased with temperature, and the strain rate at which maximum total elongation was attained increased with increasing deformation temperature.