多元多尺度增强K4169镍基高温合金的蠕变强化机理研究

先进航空发动机性能提升对其使用的大型复杂结构铸件的服役温度提出了更高要求，亟需研制700℃以上高温性能优异且工艺性能优良的等轴晶铸造镍基高温合金。项目小组基于K4169合金，通过提高其MC碳化物比例，开发了多元多尺度增强K4169合金，利用微米尺度MC碳化物和基体中γ′相的强化作用显著提升K4169合金高温性能同时保持了良好工艺性能。MC的应力承载作用是多元多尺度增强K4169合金高温性能优异的关键因素，但高温长时蠕变条件下MC和γ′相协同强化机制尚不清楚，严重制约了多元多尺度增强高温合金材料的研究与应用。本项目拟采用同步辐射X射线衍射定量研究多元多尺度K4169合金蠕变过程中多相应力分配演变行为，结合显微组织演化及长时蠕变断口附近位错组态，揭示其蠕变强化机理。相关研究工作对多元多尺度增强镍基高温合金的优化设计具有重要指导意义，可为兼具高温性能和工艺性能的新型镍基高温合金开发提供理论指导。

The service temperature enhancement of large casting with complex structure in aeroengine is demanded to meet the requirement of the performance improvement of advanced aeroengine. It is urgent to develop the equiaxed grain cast nickel base superalloy with excellent high temperature properties above 700℃ while keeping preferred processing properties. A novel muiti-scale multiphase reinforced nickel base superalloy with satisfied castability was prepared through increasing the MC carbide ratio in K4169 by the applicants. The high temperature properties of this MC/K4169 superalloy are greatly improved by the strengthening effect of micron-scale MC and nano-scale γ′ phase. The stress transfer effect from MC carbide is the key factor to enhance the high temperature performance of the MC/K4169 superalloy. However, the synergistic strengthening mechanism of MC carbide and γ′ phase in MC/K4169 superalloy under long term high temperature creep is not clear yet, which severely restricts the research and application of muiti-scale multiphase reinforced nickel base superalloy. In this project, synchrotron radiation X-ray diffraction is used to quantitatively study the stress distribution behavior during the creep of MC/K4169 superalloy. Combined with the stress distribution behavior, the microstructure evolution and the dislocation patterns near the creep fracture, the creep strengthening mechanism can be well revealed. This research work has important guiding significance for the design optimization of muiti-scale multiphase reinforced nickel base superalloy, which can provide theoretical guidance for the development of new type equiaxed grain cast nickel base superalloy with excellent high temperature properties and preferred processing characteristics.