Strain rate sensitivity and strain hardening exponent during the isothermal compression of Ti60 alloy

In this paper, the flow stress was investigated in detail during the isothermal compression of Ti60 alloy. The strain rate sensitivity and the strain hardening exponent of Ti60 alloy were calculated based on the flow stress-strain curves. The results showed that the softening effect in the alpha + beta two-phase region was more significant than that in the beta single-phase region due to the change in the deformation heat of the alloy. An initial yield drop was observed at or above 1273 K and in the strain rate range of 0.1-10.0 s(-1). The beta phase became the continuous phase above 1273 K. which led to little temperature dependence of flow stress. The maximum m value of 0.34 occurred at 1253 K and a strain rate of 0.001 s(-1) during the isothermal compression of Ti60 alloy. The strain rate sensitivity at a strain of 0.7 and a strain rate of 10.0 s(-1) decreased with increasing deformation temperature after a peak value. And the m values decreased with increasing strain rate. This phenomenon could be reasonably explained based on the microstructure evolution during the isothermal compression of Ti60 alloy. The strain hardening exponent increased with increasing deformation temperature at the strain rates of 0.001 s-1, 1.0 s(-1) and 10.0 s(-1) The variation of strain hardening exponent with strain was observed to be dependent on the strain rate and the deformation temperature. (C) 2012 Elsevier B.V. All rights reserved.