Microstructure and Texture Evolution Mechanism of Ti-3Al-5Mo-4.5V Titanium Alloy Under the Synergistic Control of Rolling-Drawing-Annealing Cooling

Abstract:

The synergistic evolution mechanism of microstructure and texture of Ti-3Al-5Mo-4.5V (TC16) alloy bar was revealed under rolling-drawing-different annealing cooling (water quenching (WQ), air cooling (AC) and furnace cooling (FC)). The results show that the initial lamellar structure of TC16 titanium alloy bar has a dual-phase structure composed of equiaxed α and β phases through dynamic recrystallization and α phase growth during two-phase rolling and annealing. The β phase and α phase form the axial silk texture of <110>//bar and //bar, respectively. Although hot drawing does not change the texture type, the hot drawing deformation leads to a significant increase in the internal grain orientation gradient, which in turn significantly weakens the texture intensity. The annealing cooling rate has a significant effect on the content of α phase, and the content of equiaxed α phase increases from 36.8vol% (WQ) to 74.9vol% (FC). The texture types of β phase and α phase at different cooling rates are consistent with the drawn texture. The α→β phase transition in the annealing heating stage retains and strengthens the original β phase texture through the Burgers orientation relationship. During the cooling process, the β→α phase transition triggers the selection of variants due to the adaptive effect, resulting in an increase in the texture strength of the α phase. It can be seen that heat treatment can retain and strengthen the rolling-drawing texture, rather than reconstruct its type. This study provides reference and guidance for the optimization of microstructure and texture of titanium alloy through the synergistic control strategy of hot processing and cooling.