Abstract
β type-Silicon Nitride (Si3N4) whiskers were mixed in organic solvent uniformly with 2124 aluminum alloy powder and fabricated into β-Si3N4 whisker reinforced aluminum composite (Vf=0.20) by hot pressing in vacuum, re-forging, and hot extrusion. Relationship between mechanical properties of the composite and strain rate at 525°C was investigated. Flow stress increases remarkably with increasing strain rate in the case of the strain rate more than 0.05s-1, where the m-value is 0.5. This is the case of superplastic deformation. Total elongation of the composite reaches 200-250% at the strain rate of 0.17s-1. Whiskers are still dispersed homogeneously in matrix after superplastic deformation. Although voids form at the interface between matrix and whisker or precipitates, the fracture surface of the composite at the strain rate of 0.17s-1 is covered by many dimples.
