Abstract The microstructural evolutions and resulted mechanical responses during isothermal holding of multipass hot deformation are essential aspects in the processing of high performance titanium alloys. In this work, isothermal holding testing was performed on a Ti-5Al-3V alloy after hot compression at temperatures of 900 °C, 930 °C and 960 °C, respectively. Stress relaxation, dilatometer measurements, and microstructure examinations (i.e. scanning electron microscope, electron backscatter diffraction and transmission electron microscope) were employed to investigate the phase transformation behaviors. The results showed a flow stress hardening phenomenon during the interrupted isothermal holding in two phase region. The post-dynamic transformation from α to β phase took place first during the early stage of isothermal holding after hot deformation. With longer isothermal holding time, the reverse transformation of meta-stable β phase to α phase was then observed. Under TEM, the reverse transformed α phases were isolated from quenched α' phases. The in-depth mechanisms of post-dynamic α to β phase transformation and reverse transformation were discussed as well.

中文翻译：

---

Ti-5Al-3V合金两相区热变形后动态α-β相变及逆相变

摘要 多道次热变形等温保持过程中的显微组织演变和由此产生的机械响应是高性能钛合金加工的重要方面。在这项工作中，分别在 900 °C、930 °C 和 960 °C 的温度下热压缩后对 Ti-5Al-3V 合金进行了等温保持测试。采用应力松弛、膨胀计测量和微观结构检查（即扫描电子显微镜、电子背散射衍射和透射电子显微镜）来研究相变行为。结果表明，在两相区间断等温保温过程中出现了流动应力硬化现象。从α相到β相的动态后转变首先发生在热变形后等温保持的早期阶段。随着等温保持时间的延长，随后观察到亚稳 β 相向 α 相的逆转变。在 TEM 下，逆转变的 α 相与淬火的 α' 相分离。还讨论了动态后 α 到 β 相变和逆相变的深入机制。