High strain rate superplasticity and deformation mechanisms of powder metallurgy 6061 Al/SiCp composites

Abstract

Metal matrix composites (MMCs) are candidate materials in the aerospace and automobile industries and have found increasing use in recent years. However, their low ductility resulting from the incorporation of reinforcement particles produces a lot of problems in forming process and limits their applications. A good solution to this problem in processing is to adopt superplastic forming (SPF). High strain rate superplasticity (HSRS) is attractive for industrial applications because SPF at high strain rates can reduce forming time greatly. High strain rate superplasticity and deformation mechanisms of powder metallurgy (PM) 6061 Al/SiCp (3 νm) composites have been investigated in this study. The extrusion ratios were 20 and 47. High temperature tensile tests were conducted over a temperature range of 853-871 K at initial strain rates of 0.001-1 s–1. Experiments show that PM 6061 Al/SiC (3 νm) composites exhibit good high strain rate superplasticity at temperatures of 853-871 K and high strain rates of 0·01-0·2 s–1. A maximum value of up to 450% was obtained at 871 K and 0·1 s–1 in the MMC3 specimen (6061 Al–10 vol.-%SiCp, extrusion ratio 47). The deformation mechanisms for HSRS were found to be dependent on the ratio of interfacial area to intergranular area β.