熔体抽拉TiAl合金纤维亚稳相形成及变形机理研究

TiAl alloys have become a new generation of high temperature structural materials for their excellent high temperature strength. However, it has seriously suspended the applications in aerospace and other fields for their bad creep strength at high temperature and not suitable for pressure processing due to microsegregation and brittleness at room temperature, respectively. This project is investigating the formation mechanism of TiAl fibers prepared by melt-extracted technology in terms of the solidification process and microstructure transformation to improve the performance of TiAl alloys. The influence of solidification parameters on the continuity and quality of TiAl fibers will be analyzed and as a consequence, the key technology of fine TiAl fibers forming process will be established. On the other hand, the migration process of the alloy elements will be investigated on consideration of the variety of solidification processes. At the same time, the microstructure, quantity and thermal stability of different metastable phases will be determined. And their evolution during various deformation processes will also be explored considering the effect of cooling rate and alloy elements. As a consequence, a metastable phase control method will be obtained. Furthermore, the investigation on tensile deformation process of TiAl fibers will be carried out at room and high temperatures. The interactions between metastable phases and the matrix will be analyzed to reveal their deformation relationship. . The successful implementation of this project will promote the development of high temperature TiAl based skin materials with high performance fibers in aerospace and the solidification of an executable technology process and theory of formation process on TiAl based fibers.

TiAl合金以其良好的高温强度成为极具应用前景的新一代高温结构材料，然而，差的高温蠕变性和室温压力加工性影响了该合金在航空航天等领域的广泛应用。本项目拟从凝固过程、组织结构方面探究熔体抽拉TiAl合金纤维形成机理。研究熔体抽拉工艺参数对纤维连续性以及纤维质量的影响规律，建立高质量TiAl合金纤维成形关键工艺；分析不同成形工艺、合金成分的TiAl合金纤维凝固组织，获得不同凝固条件下各合金元素的迁移规律；建立不同亚稳相含量、形态和位相关系的成形过程及控制方法；分析TiAl合金纤维拉伸变形过程，研究不同亚稳相与基体组织、合金元素间的相互作用，揭示TiAl合金纤维亚稳相结构、含量与变形过程间的关系。.项目成功实施将获得高性能TiAl合金纤维形成机理，为高温TiAl合金蒙皮材料的发展建立工艺过程和理论基础，有助于推动航空航天高温结构材料的发展。

本项目以耐高温Ti基合金为研究对象，通过快速凝固技术制备了不同成分的纤维和薄带，利用X射线衍射、扫描电镜、透射电镜等设备，分析了快速凝固纤维和薄带的表面形貌、组织、结构等，确定了了凝固冷却速率对组织、元素占位、偏析等的影响规律，为材料组织结构控制提供了实验参考；研究了纤维成形过程中的温度场、流场演变，分析了金属纤维成形基本工艺对纤维成形过程的影响，确定了纤维主要缺陷的形成原因；为其它金属纤维成形技术提供了理论参考。