Microstructural evolution and slip during yielding in Ti‐5Al‐5V‐2Mo‐2Cr alloy

Ti‐5Al‐5V‐2Mo‐2Cr alloy is a new type of near-β Ti alloy with excellent room-temperature mechanical properties and is an ideal material for manufacturing aircraft structural parts. In this study, analysis methods such as scanning electron microscopy and electron back-scattered diffraction were used to investigate the microstructural evolution and slip of the α and β phases during room-temperature yielding. The conditions for the phase transformation between α and β phases and the β recrystallization from 600 °C to 900 °C were revealed. The β → α phase transformation occurred below 700 °C, whereas α → β phase transformation occurred above 700 °C. Meanwhile, the residual thick α phase at the grain boundary transformed into the β phase via lamellar decomposition at 800 °C. The β phase recrystallization occurred at 750 °C. The acicular α + β mixed-grain microstructure exhibited the highest yield strength. During room-temperature yielding, the {112}< 111 > slip systems dominated the slip deformation in the β phase, but a small number of {110}< 111 > slip systems were also observed. Two types of co-deformation of the α and β phases were observed: β phase slipping along the α phase interface and β phase shearing the acicular α phase. When the α and β phases were deformed together, the slip of (−112)[−11−1] _β induced the activation of (11−2−2)[11−23] _α, whereas the slip of (211)[1−1−1] _β induced the activation of (01−10)[−2110] _α.