The softening factor c b of commercial titanium alloy wires

Abstract

Abstract The strain-rate sensitivity exponent m and activation volume υ ∗ are often used to characterize the strain-rate sensitivity of strength behavior in metals and alloys. Complications can arise when the m and υ ∗ 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 c b that characterizes the microstructural scale responsible for the observed plasticity and work hardening behavior. The softening factor c b is found to be independent of strain-rate for the Ti-alloy wires of this study. It is proposed that c b !can offer a versatile and complementary computation to the activation volume υ ∗ 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 c b-value of 14 is calculated for Ti-6Al-4V that is consistent with >10 % plasticity during work hardening whereas a high c b-value of 135 for Ti-6Al-7Nb corresponds with <4 % plasticity.