High strain rate superplasticity in friction stir processed Al-Mg-Zr alloy

Al-4Mg-1Zr extruded bar was subjected to friction stir processing (FSP), resulting in generation of a fine microstructure of 1.5 gm grain size. Superplastic deformation behavior of FSP Al-4Mg- 1Zr,alloy was investigated in strain rate range of 1 x 10(-3) to 1 s(-1) and temperature range of 350-550 degreesC and compared with that of as-rolled one. It is indicated that the FSP alloy exhibited significantly enhanced superplasticity at a high strain rate of 1 x 10(-1) s(-1), and a maximum elongation of 1280% was obtained at 525 degreesC and 1 x 10(-1) s(-1). Further, the FSP Al-4Mg-1Zr alloy exhibited excellent thermal stability at high temperature, and a large elongation of 1210% was observed at 550 degreesC and 1 x 10(-1) s(-1). Moreover, FSP resulted in a significant decrease in the flow stress in Al-4Mg-1Zr alloy. At a strain rate of 1 x 10(-2) s(-1), the flow stress similar to7 MPa) of FSP Al-4Mg-1Zr at 450 degreesC was comparable to that of as-rolled alloy at 550 degreesC. (C) 2002 Published by Elsevier Science B.V.