Flow behavior and dynamic transformation of bimodal TC17 titanium alloy during high strain rate hot compression

Abstract

The flow behavior and dynamic transformation of near β TC17 alloy with a bimodal structure were investigated by hot compression with the high strain rate range from 1 s −1 to 20 s −1 and in the temperature range from 840 °C to 900 °C in this study. The most evident discontinuous yielding and post strain hardening occur at 840 °C-20 s −1 due to its high α p volume fraction before compression and the subsequent strong work hardening effect. High strain rate can slightly promote dynamic transformation when alloy is compressed at 840 °C and 870 °C due to domination of the high flow stress and temperature raising. However, more dramatic dynamic transformation is obtained for 1 s −1 at 900 °C because the deformation heating at higher temperature/lower strain rate is less evident, and the deformation time thus maters more greatly on the phase transformation. The fine α s shows an obvious phase transformation priority than the coarse α p under all conditions due to the enhanced alloy element (Al) diffusivity resulting from enlarged α/β interface and higher dislocation (diffusion channel) density around it. The α p promotes the dynamic recrystallization of β phase while this effect becomes weaker when dynamic transformation is progressed greatly, mainly due to the inevitable stored energy consumption and reduced α p volume fraction caused by phase transformation. • Bimodal TC17 titanium alloy is hot compressed via high strain rate during α + β and β region. • Flow behavior and the morphology related phase transformation mechanism of α p and α s are analyzed. • Effect of dynamic transformation on DRX of β phase is discussed.