Strain rate sensitivity of a high-strain-rate superplastic Al6061/20SiC_Wcomposite under uniaxial and equibiaxial tension

Strain rate sensitivity exponent is an important parameter to describe the ability of a material to resist necking. Less research has been done to examine strain rate sensitivity of high-strain-rate superplastic aluminum-based composites under different stress states. In this paper, experimental investigations have been carried out to examine the deformation behavior of Al6061/20SiCWcomposite under both uniaxial and equibiaxial tension. A maximum elongation of about 505% was observed at an initial strain rate of 6.56 × 10-2s-1and at a temperature of 873 K. Similar m value is observed under uniaxial and equibiaxial tension. The results also show that m value is almost independent of true strain, which differs from conventional superplastic alloys. It is believed that no significant concurrent matrix-grain growth is one of the reasons for the phenomenon. The reasons for a large discrepancy between the stress-strain rate curves under uniaxial and equibiaxial tension are also discussed in the paper.