Effect of solution and aging treatment on microstructure, texture and impact property of Ti662 titanium alloy thick plate

Abstract

In this paper, the effects of solution temperature (920 °C–960 °C) and aging treatment (560 °C) on the microstructure, crystallographic texture, impact properties and fracture behavior of Ti662 titanium alloy were systematically studied. The results show that with increasing solution temperature, the primary α phase gradually dissolves and becomes equiaxed, and disappears completely upon entering the β single‐phase region, where the microstructure transforms into a large number of α′ phases and coarse β grains. Aging treatment promotes the decomposition of metastable phases and the precipitation of a uniform and fine secondary α phase, the amount of which increases with increasing solution temperature. XRD confirmed that the solution‐treated state contained primary α phase, α′ phase and α′′ phase, which were transformed into primary α phase, secondary α phase and residual β phase after aging. Texture analysis showed that all samples exhibited an R‐type texture, with texture intensity increasing with solution temperature (from 2.89 to 4.99), and further increasing to 6.34 after aging, which is attributed to the thermal stability of the texture and the orientation inheritance of the precipitated phase relative to the matrix. Impact performance tests show that the impact absorbed energy of both the solution‐treated and solution‐aged states decreases with increasing solution temperature, and the solution‐treated state consistently outperforms the solution‐aged state. This change depends mainly on the crack initiation stage. The primary α phase, as a plastic phase, can effectively coordinate deformation, but the reduction in primary α phase causes a significant decrease in the crack initiation work, while the path deflection induced by the α′ phase during the crack propagation stage contributes less to energy absorption. Fracture analysis shows that increasing solution temperature causes the fracture mode to change from equiaxed dimple to rock‐like brittle fracture, and secondary cracks increase after aging. Although this does not change the embrittlement trend, it can hinder main crack propagation. In summary, optimizing the solution temperature to regulate the content of primary α phase is the key to improving impact performance.