Publications Details

The softening factor cbof commercial titanium alloy wires

Jankowski, Alan F.; Chames, J.M.; Gardea, A.; Nishimoto, R.; Brannigan, E.M.

The strain-rate sensitivity exponent m and activation volume υa - are often used to characterize the strain-rate sensitivity of strength behavior in metals and alloys. Complications can arise when the m and υa - values become indeterminate, due to factors such as an inherent scatter in the mechanical property data. The study of commercial Ti-alloy wires is considered wherein to overcome this limitation, the formulation of the Kocks-Mecking (K-M) model is modified to provide a parameter cb that characterizes the microstructural scale responsible for the observed plasticity and work hardening behavior. The softening factor cb is found to be independent of strain-rate for the Ti-alloy wires of this study. It is proposed that cb !can offer a versatile and complementary computation to the activation volume υa - since its formulation includes the yield and ultimate strength values along with the plastic strain. For the tensile testing of Ti-alloy wires, a low cb-value of 14 is calculated for Ti-6Al-4V that is consistent with >10as % plasticity during work hardening whereas a high cb-value of 135 for Ti-6Al-7Nb corresponds with <4as % plasticity.