SUPERPLASTICITY AND SUPERPLASTIC DEFORMATION MECHANISM OF A SIC_p/2024Al COMPOSITE

摘要

A highest elongation of 290% and a maximum m value of 0.49 were recorded at a strain rate of 8.33X 10~(-4) s~(-1) at 793K for an IM SiC_p/2024Al composite. The equiaxed structure was observed at the initial stage of superplastic deformation. With increasing elongation, the sizes of grains gradually decreased and grain shape coefficient gradually increased. But during superplastic deformation, grains fundamentally remained equiaxed structure. At the moment of failure, grain shape coefficient increased to 1.58. This indicated that macroscopic deformation of the composite was not caused by the grain elongation, but mainly by the grain boundary sliding. Dislocation and an appropriate liquid phase at matrix-reinforcement interfaces and/or grain boundaries played a positive role to grain boundary sliding.