Processing of high-strain-rate superplastic Si3N4w/Al–Mg–Si composites

Abstract
Effects of reduction, reinforcements, and dynamic precipitation on grain refinement by hot extrusion have been investigated in a Si3N4w/Al-Mg-Si (6061) composite by tensile tests and microstructural investigation. The grain refinement was attributed to an interaction of recrystallization and dynamic precipitation, which was enhanced by reinforcements. Not only fine-grained microstructure, but also relaxing stress concentrations which are caused at matrix/reinforcement interfaces during superplastic flow are required to attain large elongations. Partial melting resulting from segregation plays an important role in relaxing the stress concentrations. DSC investigations revealed that the degree of segregation was increased by hot extrusion.