High Strain Rate Superplasticity in 10vol. SiC Particulate Reinforced AZ31 Magnesium Alloys

摘要

AZ31 magnesium matrix composites reinforced with 10vol.% SiC particulate (2 μm) were prepared by stirring-cast under high purity argon atmosphere, then extruded with a reduction ratio of 49:1 at 663K. Superplasticity of the composites was investigated at temperature range from 638K to 838K and strain rate from 2.08 × 10~(-3) s~(-1) to 5.21 × 10~(-1) s~(-1). High strain rate superplasticity has been obtained in the composites at 798K with a strain rate of 2.08 × 10~(-1) s~(-1) and at 813K with a strain rate of 5.21 × 10~(-1) s~(-1), respectively. The maximum total elongation of 228% was obtained at a strain rate of 2.08 × 10~(-1) s~(-1). The strain rate sensitivity exponent (m) which was higher than 0.3, were observed when the strain rate was higher than 10~(-1) s~(-1) at 798K. Increasing the test temperature to 813K, the maximum total elongation exceeding 195% was achieved at a higher strain rate of 5.21 × 10~(-1) s~(-1) than at 798K. It indicates that superplasticity in such a kind of composite can be obtained by adjusting the strain rate and tensile test temperature. One kind of magnesium matrix composites may show high strain rate superplasticity under two tensile strain rates, and correspondingly at two optimum test temperatures. The higher the tensile strain rate is, correspondingly, the higher the optimum temperature is, too.