Flow behavior analysis and prediction of flow instability of a lamellar TA10 titanium alloy

Abstract

The flow behavior analysis and prediction of flow instability of TA10 titanium alloy were investigated during isothermal compression. TA10 titanium alloy was prepared by an electron beam cold hearth, and the TA10 titanium alloy ingot had a lamellar structure. The ingots were subjected to isothermal compression by a Gleeble-1500 thermomechanical simulator at 800–1050 °C, the strain rate range was 0.01–1 s −1 and the height reduction was 60%. An analysis of the flow stress-strain curves showed that discontinuous yielding behaviors occurred when the deformation temperature exceeded the β-transus temperature, and flow softening occurred at all deformation temperatures except 900 °C. The sample microstructure was studied, and the microstructural evolution was summarized. When the deformation temperature was 950 °C and the strain rate was 1 s −1 , an adiabatic shear band appeared in the microstructure, and the element distribution in the adiabatic shear band was analyzed. Based on the dynamic material model, processing maps under Prasad's and Murty's instability criterion were established. Combined with the microstructure and instability situation, the applicability of Prasad's instability criterion in lamellar TA10 titanium alloy was clarified. The suitable processing parameters were 1020–1050 °C and 0.1–1 s −1 or 875–950 °C and 0.01–0.05 s −1 . Combined with electron back-scattered diffraction, the flow-softening mechanism was analyzed, and the results revealed that the lamellar kinking, deformation heat and dynamic recovery were the flow-softening mechanisms when the deformation temperature was lower than the β-transus temperature, and when the deformation temperature exceeded the β-transus temperature, the dynamic recovery was only the flow-softening mechanism. • The microstructural evolution, flow stress-strain curves and flow-softening extent were analyzed in detail. Only one flow instability was found and the type of flow instability was the adiabatic shear band. • The flow instability was predicted by establishing Prasad's and Murty's processing maps and the accuracy of the process maps was compared. • Combined with the flow-softening extent, the flow-softening mechanism was analyzed by EBSD in detail. The flow-softening mechanism changed with deformation temperatures and strain rates.