Effect of Hot and Cold Compression Deformation on the Slip and Twinning Behavior of Ti–5Mo–4Fe Alloy

Abstract

Metastable β titanium alloys with a BCC structure readily undergo slip deformation because many available slip systems and high stacking fault energy allow dislocations to move freely. However, during room-temperature deformation, higher strain energy is accumulated than during deformation, while the available thermal energy is insufficient to relieve stored energy. Consequently, auxiliary deformation mechanisms, such as twinning, are activated to accommodate and promote plastic deformation. Among the twinning modes, the {112}<111> twin is more difficult to activate than the {332}<113> twin because it requires a higher critical resolved shear stress. In this study, the slip and twinning behaviors during hot and room-temperature compression deformation were investigated. Hot compression deformation was performed using a multi-pass hot-rolling process. As the number of rolling passes increased, the initially recrystallized grains with specific orientations became aligned into orientations favorable for slip activation. Furthermore, the {110}<111> slip system was preferentially activated in grains with a {100}[110] orientation. In contrast, room-temperature compression exhibited excellent compressive strength and ductility, accompanied by the activation of the {112}<111> twin in grains with a {111}[110] orientation. These results indicate that both slip and twinning are preferentially activated in grains with a [110] direction during hot and room-temperature deformation.