β型γ-TiAl合金中B2相调控及其对高温蠕变性能的影响机制

β型γ-TiAl合金中B2/β相具有良好的热变形能力，但是有序的B2相恶化合金的机械性能，尤其是高温抗蠕变性能。因此需要对B2相进行精确调控以改善合金性能。以往研究多是采用热等静压/热处理手段降低B2相含量，但通常无法完全消除B2相，并忽略了初始冷却过程对B2相形成的重要影响。对此，本项目通过受控凝固与热处理相结合，实现对B2相微观结构与分布的控制，通过热力学和动力学分析，揭示B2相微观结构的形成机制，以及B2相的分布规律，阐明热处理过程中B2相的演变规律。基于受控凝固和热处理获得的组织，研究B2相微观结构和分布与合金蠕变行为之间的相关性，明确具有高抗蠕变性能B2相的微观结构与分布。本项目研究成果可为B2相微观结构与分布的精准调控提供理论依据，对改善β型γ-TiAl合金高温抗蠕变性能具有指导意义。

The β/B2 phase exhibits excellent deformability in β-solidifying γ-TiAl alloy, but the ordered B2 phase would deteriorate the mechanical properties of the alloy, especially the high-temperature creep resistance. Therefore, precise control of B2 phase is required to improve the mechanical properties of the β-solidifying TiAl alloy. In the past, the researches on reducing the content B2 phase are limited to hot isostatic pressing or heat treatment, but it is often difficult to eliminate the B2 phase completely and neglects the significant influence of initial cooling process on the formation of B2 phase. For these reasons, the controlled solidification rate and heat treatment are combined to control the microstructure and distribution of B2 phase in this project. Based on the thermodynamics/ kinetics calculation, the formation mechanism of the microstructure of B2 phase and distribution of B2 phase will be revealed, and the evolution rule of B2 phase will be clarified during heat treatment. Based on the optimized microstructure and distribution of B2 phase, the correlation among the microstructure and distribution of B2 phase and creep behavior will be studied, and the microstructure and distribution of B2 phase with high creep resistance were determined. The research results of this project can provide a theoretical basis for the accurate regulation of the B2 phase microstructure and distribution, and have a guiding significance for improving the creep resistance performance of the β-solidifying γ-TiAl alloy at high temperature.