单晶高温合金再结晶及其损伤机理

Single crystal superalloy blade is the key component in hot section of an aero engine. Recrystallization (RX) is a serious defect affecting the yield rate of single crystal blade and the safe service of aero engine. At present, the control technology and standard of RX in single crystal blade are not thoroughly understood in China. This project intends to study the cause of RX in hollow single crystal blades with complex geometry, and establish the quantitative relationship between process parameters, blade structure and RX; to reveal the recovery, nucleation and growth mechanism of RX in single crystal superalloys, especially the formation mechanism of the large-size RX grains. The present project will also focus on the evolution behavior of RX layer on the blade surface during long-term engine tests and long-term creep tests, and try to explore the creep damage mechanism of single crystal blade containing RX during long-term service. A long-term creep damage model related to RX will be proposed. .The RX control technology of single crystal superalloy blade will be put forward and preliminarily verified based on above information. The data and method obtained will strengthen the theoretical foundation for alloy design, safety evaluation of single crystal blade and the improvement of RX related technical standards.

单晶高温合金叶片是航空发动机的关键热端部件。再结晶是影响单晶叶片铸造合格率和航空发动机安全服役的严重缺陷，目前国内对单晶叶片再结晶的控制技术和标准尚缺乏深入认识。本项目拟深入研究复杂空心单晶叶片再结晶诱因，建立工艺参数-叶片结构-再结晶之间的量化关系；揭示单晶高温合金再结晶回复、形核和长大机理，特别是大尺寸再结晶晶粒的形成机制；分析发动机长寿命试车中叶片表面再结晶层的演化规律，结合单晶合金长时蠕变测试，揭示长寿命服役中含再结晶叶片的蠕变损伤机理，构建再结晶相关的长寿命蠕变损伤模型。.在此基础上，提出单晶高温合金叶片再结晶控制技术，并进行初步验证；积累数据，完善方法，为单晶合金成分优化、单晶叶片安全服役评估和再结晶相关技术标准的制定和完善奠定理论基础。

再结晶是单晶高温合金的严重缺陷，严重影响单晶叶片的合格率和安全服役。.本项目发展了热弹塑性各向异性本构模型，发现高温塑性变形是单晶铸件再结晶的诱因，且变形发生在1150~1230℃范围内。进一步建立了单晶叶片结构-工艺参数-再结晶的关系。在此基础上，开发了单晶叶片再结晶预测软件，提出了减少单晶叶片再结晶的建议。.本项目阐明了单晶高温合金高温变形、回复、再结晶形核、长大机制，明确了Re对单晶合金再结晶的影响。本项目阐明了变形机理对单晶高温合金再结晶的影响。在此基础上，本项目提出了单晶高温合金再结晶倾向性判据，即临界KAM判据，并进行了验证。.长时蠕变过程中，由于再结晶、氧化造成的贫化区、晶界迁移的交互作用，再结晶对长时蠕变寿命的影响明显大于短时蠕变。而中温长时蠕变时，由于氧化造成的贫化极大地减少，其长时蠕变寿命与短时蠕变寿命差异不大。.本项目的研究，将进一步丰富再结晶基础理论，为单晶叶片安全服役、技术标准的完善、单晶叶片再结晶缺陷的控制，指明了方向。本项目对推动单晶叶片从“有”到“优”、从“有”到“稳”，提高发动机长寿命服役稳定性具有重要意义。