(1. 西北工业大学 凝固技术国家重点实验室，西安 710072；
2. 西部超导材料科技股份有限公司，西安 710016)
摘 要: 系统研究了Ti-5553、Ti-55531和Ti-7333近β钛合金在β单相区固溶水冷+时效(SWA)、固溶+直接时效(SA)以及固溶缓冷+时效(SFA)等热处理制度下次生α相的形核位置、形貌和分布，探讨了近β钛合金的次生α相形核机制。结果表明：3种合金在SWA过程中，针状α相在晶界和晶内同时形核；在SFA过程中，片层状α相优先占据晶界位置析出；在SA过程中，点状α相在基体上弥散分布；此外，由于含有较多的慢扩散Mo元素，Ti-7333合金表现出较慢的时效响应，时效过程中α相形核位置分布不均匀，易于沿晶界及位错析出。EBSD结果分析显示：β晶界处α相的析出受晶界能影响，优先在大角晶界析出。
关键字: 近β钛合金；热处理；次生α相；形核；EBSD
（1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;
2. Western Superconducting Technologies Co., Ltd, Xi’an 710016, China）
Abstract:The nucleation place, morphology and distribution of α phase in different process routes of the near-β titanium alloy (Ti-5553, Ti-55531 and Ti-7333 alloys) were investigated systematically. The results show that the needle-like secondary α precipitate morphology forms after solution treatment above β transus followed with ageng treatment (SWA). The dot α precipitation with different variants precipitate within β grains as well as along β grain boundaries during β solution follow by direct ageing (SA). In addition, the slower ageing respond and a nonuniform distribution of α precipitate are observed in Ti-7333 alloy, which results from the more slow-diffusing element Mo in Ti-7333 alloy. In the condition of β solution followed by furnace cooling and ageing (SFA), the α phase preferentially nucleates at grain boundaries. The EBSD analyses reveal that the grain boundary α precipitation is strongly influenced by β grain boundary energy which meant that grain boundary α tends to form preferentially at high energy grain boundaries (high-angle grain boundaries).
Key words: near-β titanium alloy; heat treatment; secondary α precipitation; nucleation; EBSD
