稳定 γ' 相强化的低密度新型Co基超合金的设计、定向凝固及性能研究

本项目针对航空领域用无W低密度Co基超合金的开发，开展第一性原理计算和相图热力学计算，建立Co-Ni-Cr-Al-V-Ti-Ta合金系的热力学数据库。利用CALPHAD方法，计算预测多元系稳定的γ/γ′两相区可能存在的成分和温度范围，同时，通过计算γ/γ′相的体积分数、合金的熔点以及平衡凝固和非平衡凝固过程等信息，利用理论计算与实验研究相结合的方法优化合金成分，设计具有稳定γ′相强化的新型低密度Co基超合金，并提出稳定γ′相强化的低密度新型Co基超合金的成分设计准则。在此基础上对新型Co基超合金的定向凝固工艺开展深入研究，解明定向凝固工艺参数对成分偏析及后续γ′相析出的影响，建立组织演变与使役性能间的关系，为发展具有我国自主知识产权的稳定γ′相强化的低密度新型Co基超合金及其制备技术提供理论基础。

In this project, in order to develop the novel Co-based superalloy with lower density used in aviation field, the thermodynamic database of the Co-Ni-Cr-Al-V-Ti-Ta alloy will be established by combining with the first-principle and phase diagram calculation. The CALPHAD method will be used to predict the possible composition and temperature range for the co-existence of the γ and γ′ phases in multicomponent system. At the same time, the Co-based superalloys strengthened by stable γ′ phase will be designed by calculating the volume fraction of the γ′ phase, the melting temperature as well as the equilibrium and nonequilibrium process of solidification. Based on the investigation of the thermo-stability of γ′ phase in the Co-based superalloys and the optimization of the alloy compositions carried out by the combination of theoretical calculation and experimental investigation, the design criteria of the novel low-density Co-based superalloys reinforced by stable γ′ phase will be proposed. The directional solidification techniques and the effect of the directional solidification parameters on the solute segregation and the precipitation of the γ′ phase will be further investigated. The relation between the microstructure and performance will be established in order to provide theoretical basis for the development of the novel low-density Co-based superalloys reinforced by stable γ′ phase that possess our own intellectual-property rights.