β/α 转变温度附近恒温处理对铸造 Ti65 合金显微组织的影响

Ti65 is a near α high-temperature titanium alloy independently developed in China. When used as a casting alloy, its coarse lamellar structure is difficult to control through hot isostatic pressing and heat treatment processes. This article investigated the effect of constant temperature treatment from the single-phase zone cooling to 940~1 020 ℃ of near the transition temperature of β/α on the microstructure of Ti65 alloy. The results showed that the α lamellae in Ti65 alloy was coarsened and fragmented after constant temperature treatment at 960~1 000 ℃ /30 min, forming a "special bimodal microstructure" consisting of coarsened and fragmented α lamellae and fine α lamellae. The coarsening and fragmentation of α lamellae occurred during the high temperature holding period, while the fine α lamellae were formed during the subsequent cooling process. The most obvious coarsening and fragmentation of the α lamellae occurred after 960 ℃ /30 min constant temperature treatment, while the morphological characteristics of the lamellae remained basically unchanged during the constant temperature treatments at 940 ℃ and 1 020 ℃, with only the thickness of the lamellae being altered. This work could provide new ideas for regulating the coarse and large layer structure of cast titanium alloys.