钴基合金具有初熔温度度高、抗热腐蚀性能好以及优异的耐磨损疲劳性能、热疲劳性能和焊接性能等优点。因此新型γ′沉淀强化Co-Al-W基合金引起了广泛重视，有望发展成为新的高温合金体系。高温组织稳定性决定了合金应用前景。本项目首先以Co-Al-W-X (X=C, B, Cr, Re, Ta和Hf) 四元单晶合金为研究对象，采用第一原理计算四元单晶合金中γ′相热力学稳定性，制备典型四元合金单晶试样，并进行高温长期时效，然后采用光学显微镜、扫描电镜、透射电镜、电子探针、XRD衍射和DSC等测试手段，系统研究合金元素对合金组织稳定性、固液相线温度、γ′相体积分数、形态、尺寸和成分等的影响。在此基础上，设计制备固溶、碳化物和沉淀相强化兼备的新型Co-Al-W基单晶合金，研究典型合金元素交互作用对高温组织稳定性影响，揭示合金组织稳定性演变规律，提高合金高温力学性能，为新型钴基合金成分设计奠定理论基础。

Co-based superalloys possess higher incipent melting temperature, excellent resistance to hot corrosion, wear fatigue resistance, thermal fatigue resistance and weldability. New γ′-strengthened Co-Al-W based alloys have therefore attracted extensive interest, which can be developed for new system of superalloys. Prospective applications of the Co-Al-W based alloys are mainly determined by the microstructure stability at elevated temperature. In this project, Co-Al-W-X (X=C, B, Cr, Re, Ta and Hf) quaternary single crystal alloys are investigated as target material. A first-principles study of thermodynamic stability of γ′ precipitates in those quaternary systems is carried out. Then single crystal specimens are made of typical quaternary alloys by Bridgman directional solidification technique. Then the specimens are exposed at elevated temperature for prolonged ageing. By means of OM, SEM, TEM, electron probe, X-ray diffraction and DSC, the effect of alloy agent additions on the microstructure stability, solidus and liquidus temperatures, volume fraction, morphologies, size and component of γ′ precipitates, etc. are systemically investigated. Further, new Co-Al-W based single crystal alloys jointly strengthened by solution, carbide and precipitates will be designed and prepared to study interaction of typical elements on microstructure stability. The laws of variable microstructure stability with elements will be summarized in detail, which provide the fundamentals for improving mechanical properties and designing for the Co-Al-W based superalloy.