预变形对钛合金两相区冷却过程中次生α相形核的影响

同步、精细化调控钛合金初生α相和次生α相的组织状态，不仅是优化其力学性能的关键，也是钛合金两相区热处理领域的一大难题。预变形可调控次生α相的形核过程，进而调控次生α相和初生α相的组织状态。因此，研究预变形对钛合金两相区冷却过程中次生α相形核的影响具有一定的工程和科学意义。本项目首先研究预变形对初生α相和β相含量、晶粒尺寸、位向关系和晶体缺陷等组织状态的影响；其次，研究预变形影响次生α相几何形貌、含量和晶粒尺寸的宏观规律；然后，通过分析次生α相、初生α相和β相三者之间的位向关系，研究次生α相的形核位置、以及形核位置的选择准则；最后，综合分析预变形对次生α相形核影响的微观机制。本项目一方面有望在钛合金次生α相形核的晶体学条件方面取得新进展，完善钛合金固态相变理论；另一方面为钛合金热处理制度的制定和新工艺的开发奠定理论基础，促进钛合金微观组织精细化调控技术的发展。

The synchronous and precise control of primary α phase and secondary α phase not only plays a key role to optimize the mechanical properties, but also be a serious problem in the heat treatment during the α+β phase region of titanium alloy. The investigation about the effect of pre-deformation on the nucleation of secondary α phase in the α+β phase region of titanium alloy can help to solve this serious problem. Firstly, this project will investigate the effect of pre-deformation on the content, grain size, orientation relationship and crystal defect of primary α phase and β phase. Secondly, the macro effect of pre-deformation on the morphology, content and grain size of secondary α phase well be investigated. Thirdly, based on the examination and analysis of the orientation relationship among the secondary α phase, primary α phase and β phase, the nucleation site and its selected criteria of secondary α phase will be investigated. Finally, based on the synthetical analysis of the previous results, this project will investigate the influencing micro-mechanism of pre-deformation on the nucleation of secondary α phase. This project would improve the solid phase transformation theory of titanium alloy depending on the progress in crystallography criteria for the nucleation of secondary α phase. Meanwhile, this project would benefit the development of precise control of microstructure, which lays the theoretical foundation for the design and new development of process for the heat treatment of titanium alloy.