Cyclic deformation responses in α-phase of a lamellar near β-Ti alloy

Abstract

A lamellar near β-Ti alloy was subjected to cyclic tensile loading at room temperature. Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) investigation revealed that the deformation mechanisms of α-phase were found to be changing with increasing loading cycles, from mechanical twinning to martensite transformation. To be specific, at the beginning of straining, the formation of mechanical α-twins was the dominant deformation mechanism to accommodate the applied strain. As the increasing cycles, the secondary twin and hierarchical structure formed in α laths. During further straining, the noticeable groove was observed at the α/β grain boundary. Meanwhile, dispersed nanosized α" martensite phase formed in the α plate and the number of α-twins sharply decreased at this stage. This work will provide a basis for the enhancement of load bearing capabilities of near β-Ti alloys.