Discontinuous yielding behavior in the near-α Ti-3Al-2.5V alloy

The yielding behavior of a near-α Ti-3Al-2.5V alloy, subjected to cold rolling and annealing at various temperatures, has been investigated. As the annealing temperature rises from 550 °C to 840 °C, the recrystallization degree and grain size of the Ti-3Al-2.5V alloy increase. The yielding behavior of Ti-3Al-2.5V alloy exhibits a transition from continuous yielding to discontinuous yielding, characterized by a drop in the yield point and the emergence of a stress plateau. The predominant deformation mechanism during the yielding stage of fully recrystallized samples is <a>-type prismatic planar slip. The yield drop and the stress plateau arise different mechanisms. Analysis of the initial microstructure and the loading-unloading experiments reveal that the drop in the yield point is attributed to the reduced dislocation density achieved from the high-temperature annealing. The stress plateau is associated with the propagation of the Lüders band, during which the dislocation accumulation and annihilation are related to the grain size. The large grain size of the 840 °C-annealed sample leads to the enhanced work-hardening ability and the disappearance of Lüders plateau.