钛合金片状α相球化的晶体取向依赖性及协调演变行为

The globularization of the lamellar α of titanium alloy is a critical step to manufacture dual-property blisk of aerospace engines. However, most researches including globularization of titanium alloy only pay attentions to external factors including strain, temperature, etc, rather than the effect of own crystal orientation and matrix β. It is difficult to control the homogeneity and stability of the globularized microstructure. In view of these questions, this project raises research content of crystal orientation dependent of globularization of the lamellar α and coordinate evolution behavior for titanium alloy. This project will control morphology of β phase through processing in single β phase field, and further influence variant selection of α phase. In this case, the lamellar α under different conditions have different crystal orientation features. Then the effect of crystal orientation on globularization of the lamellar α is studied via deformation in α+β phase field. Such investigation is expected to expound crystal orientation dependent of globularization of the lamellar α phase, and reveal the globularization mechanisms. Also, the interactive relationship of microstructure evolution of the lamellar α and β phase is researched and the effect of the initial morphology of β phase is analyzed. Finally, microstructure evolution of α and β phases will be taken into account in order to develop coordinate evolution mechanism of α/β phase. This project will solve the problems of the uniformity and instability of the globularized microstructure, and realize accurate control on globularization process. This research will promote in-depth development of processing theory of titanium alloys, as well as have important implications for development of dual-property blisk.

钛合金片状α相球化是制造航空发动机双性能整体叶盘的关键步骤。目前大部分研究仅关注应变、温度等外部因素的影响，而忽略自身的晶体取向及基体β相的作用，导致球化组织的均匀性、稳定性难以控制。针对此问题，本项目提出了钛合金片状α相球化的晶体取向依赖性及α/β相协调演变行为的研究内容，拟通过β单相区加工控制β相形态，进而控制α相的变体选择，使不同条件下α相具有不同的晶体取向特征，然后通过α+β两相区变形，研究晶体取向对片状α相球化的影响规律，阐明片状α相球化过程与晶体取向之间依赖关系，从晶体学角度揭示片状α相球化机理；研究片状α相球化与β相演变的相互作用关系，并分析初始β相形态对这种关系的影响，揭示α/β相的协调演变机理。通过本项目研究将解决球化过程中组织不均匀、不稳定的问题，实现对球化过程的准确控制，对钛合金球化理论的发展及双性能整体叶盘的制备具有重要意义。

钛合金片状α相球化是制造航空发动机双性能整体叶盘的关键步骤。目前大部分研究仅关注应变、温度等外部因素的影响，而忽略自身的晶体取向及基体β相的作用，导致球化组织的均匀性、稳定性难以控制。针对此问题，本项目进行了钛合金片状α相球化的晶体取向依赖性及α/β相协调演变行为的课题研究，开展了不同条件下α相的析出规律及机理研究，晶体取向对片状α相球化的影响规律及机理研究，片状α相球化过程中与β相的协调演变行为研究。通过本项目研究，得到的主要结论如下：单相区热加工后的冷却决定α相的析出过程，晶界α相最先析出，其形貌受晶界α相与相邻非Burgers β晶粒的取向差影响，取向差越大，析出的晶界α相形变程度越大；后续析出的晶内α相受晶界α相和原始β晶粒的影响，在与β基体保持Burgers取向关系的前提下，邻近晶界的晶内α相会最大程度的与晶界α相的晶体取向保持一致，可通过冷速调节晶界α相和晶内α相的析出过程。片状α相的球化过程受自身的晶体取向的影响，α相会通过滑移和晶体旋转的方式完成球化过程，其[0001]方向越靠近压缩方向时，球化越不容易发生。片状α相球化过程中晶体旋转的转轴为[0001]或者[11-20]。[0001]的转轴是柱面滑移所引起的，而[11-20]的转轴是α/β相的协调演变所导致的。变形过程中，α相和β相是相互影响的，大的塑性变形尽快会破坏α/β相之间的Burgers取向关系，但他们仍然会最大程度地保持[111]β//[11-20]α，以此来降低系统自由能。此外，α相的球化与β相的再结晶相互促进。上述研究成果可以为解决球化过程中组织不均匀、不稳定的问题提供理论指导，可推广应用于钛合金双性能整体叶盘制备及锻造领域。