Variant selection mechanism of α phase associated with initial texture and cooling rate in near-α titanium alloy Ti65

The elucidation of the impact of the initial texture and cooling rate on the variant selection (VS) mechanism of alpha-phase in titanium alloys is essential for optimising their microstructure and mechanical properties. In this study, Ti65 foils featuring three different initial textures underwent annealing in the alpha + beta phase region, followed by cooling at three different rates. Under slow cooling conditions (furnace cooling), the primary mechanism governing texture evolution of alpha-phase is the grain growth of the primary alpha (alpha p) grains. Consequently, the effect of the initial texture on the texture evolution of alpha-phase under slow cooling is ascribed to variations in the alpha p grains in the samples after heat treatments. Additionally, standard disorientation angle theta m distribution maps of the alpha texture under different beta textures are developed to predict the texture of the alpha p grains. In contrast, during rapid cooling (200 degrees C/min cooling and air cooling), texture evolution of alpha-phase is driven by the precipitation of the secondary alpha (alpha s) grains. In this case, a change in the cooling rate has no effect on the VS mechanism of alpha-phase at the alpha p/beta and beta/beta boundaries, but it changes the VS mechanism of alpha-phase at the parent beta grain interior. Therefore, the influence of the initial texture on VS mechanism of alpha-phase under rapid cooling varies with cooling rates, depending on the ratio of alpha s grains precipitated at alpha p/beta and beta/beta boundaries to the alpha s grains precipitated at the parent beta grain interior.