Microstructure and superplasticity in a stir — Cast SiCp/2024 aluminium composite

Abstract

Aluminium matrix composites reinforced with ceramic whiskers or particles have a high specific strength and modulus in addition to good wear resistance and heat resistance. They have shown considerable promise in structural applications, but one of the main drawbacks of the composite is the ductility, which leads to the poor formability, and thus limits their applications. Superplastic forming is a viable technique that is used to solve this problem. A number of aluminium base composites can exhibit superplasticity. Until now, almost all of the composites in superplastic studies were prepared by the powder metallurgy (PM) method. This method causes the composites to have very fine grains (about 1 [mu]m) and fewer microstructural defects; as a result, they exhibited high strain rate superplasticity. Studies on the superplasticity in ingot metallurgy (IM) aluminium matrix composites are rare, but are equally important. Because IM is a low cost method of preparing aluminium matrix composites, it will play an increasingly more important role in the future applications of the composites. In this work the authors investigated the microstructure and superplasticity of a IM 2024 aluminium matrix composite, reinforced with silicon carbide particles (SiCp/2024). They thermomechanically treated the composite by hot forging and extrusion, obtainedmore » a superplastic elongation of 685% at an initial strain rate of 5 [times] 10[sup [minus]4]s[sup [minus]1], with a 788K temperature. They also observed and analyzed the microstructure of this composite.« less