Strain rate sensitivity of a high-strain-rate superplastic Al6061/20SiCW composite 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 A16061/20SiC(W) composite under both uniaxial and equibiaxial tension. A maximum elongation of about 505% was observed at an initial strain rate of 6.56 X 10(-2) s(-1) and 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. (C) 2001 Elsevier Science B.V. All rights reserved.