TiAl合金长周期堆垛有序（LPSO）相的热稳定性及高温蠕变行为研究

TiAl合金密度低、弹性模量高、高温性能好，是先进航空发动机低压涡轮叶片的首选材料。但其强度和塑性差，服役温度仅为600~800℃，极大地制约了TiAl合金的进一步发展应用。申请人在研究中发现，利用激光同轴送粉增材制造技术获得的LPSO相能够有效提高TiAl合金的室温强度和塑性，但LPSO相的高温表现，特别是LPSO相的热稳定性及其对TiAl合金高温蠕变行为的影响目前仍不清晰。因此，本项目拟通过第一性原理计算与热处理实验结合的方法探究LPSO相的热稳定性，明确其失稳条件及分解过程；研究TiAl合金高温蠕变过程中LPSO相对位错组态、裂纹萌生及扩展的影响规律，从微观的角度揭示LPSO相对蠕变变形及断裂过程的内在影响机理。本项目将为TiAl合金显微组织的优化与综合性能的提升提供理论依据。

TiAl alloys are the most preferred materials for low pressure turbine blades of advanced aero engines due to their low density, high elastic modulus, and excellent high-temperature properties. However, its poor ductility, low strength, and relative low service temperature (600~800℃) greatly limit the development of TiAl alloys. In the pre-research, we found that the laser coaxial powder feeding additive manufacturing technology could be used to fabricate TiAl alloys containing LPSO phase, and their strength and ductility are greatly improved. However, the high-temperature performance of LPSO phase, especially its thermal stability and its influence on high-temperature creep resistance still remain unclear. This project intends to explore the thermal stability of LPSO phase and clarify its instability conditions and decomposition process by the approaches of first principle calculations and heat treatment experiments. Then, the dislocation configuration, crack initiation and propagation will be investigated during the high-temperature creep process, which reveals the inner influence mechanism of LPSO phase from the perspective of creep deformation and cracking. This project will provide a theoretical basis for optimizing the microstructure and improving the comprehensive properties of TiAl alloys.