微量元素B和Zr对镍基高温合金流动性和强化机制研究

With the development of aeroengine, cast forming and performance optimization of the complex and thin-walled lightweight superalloy integral investment castings have become a major engineering problem that requires urgent solutions. Due to the wide window of solidification temperature range of superalloys and the complex characteristics of castings structure, it is difficult to coordinate and control the complete filling and grain boundary strengthening of the castings. In this project, the trace elements B and Zr will be regulated to improve the fluidity of the superalloy without reducing its mechanical properties, and achieve good mold filling and grain boundary strengthening at the same time under the condition of low casting temperature. A comprehensive study of the influence of B and Zr on the solidification behavior and fluidity of superalloys, the characterization method of the fluidity of superalloys and the effective way to improve the fluidity will be established. The influence of trace element regulation on the fluidity of superalloy is clarified, and the relationship among composition, solidification characteristics and fluidity of superalloy will be obtained. Furthermore, the influence rules of composition, microstructure and properties of superalloy are systematically studied, and the strengthening mechanisms of B and Zr in superalloy are clarified in detail. The research results will enrich and develop the superalloy performance optimization and corresponding solidification theory, and further provide theoretical guidance for the research and application of the manufacture of aeroengine key components.

随着航空发动机的发展，结构复杂化和薄壁轻量化高温合金整体铸件的铸造成型与性能优化控制成为迫切需要解决的重大工程问题。由于高温合金凝固温度区间宽以及铸件结构复杂等特点，该类铸件完整充型和晶界强化难以协调控制。本项目将通过调控高温合金中微量元素B和Zr的含量，探索在不降低合金力学性能的前提下改善其流动性，在低的浇铸温度条件同时实现良好充型和晶界强化。通过深入研究微量元素B和Zr对高温合金凝固行为和流动性的影响规律，建立高温合金流动性的表征方法及改善流动性有效措施，明确微量元素B和Zr调控对高温合金流动性的作用机理，获得合金成分-凝固特性-流动性的响应关系。系统研究合金成分-组织-性能之间的影响规律，进而明确微量元素B和Zr在高温合金中的强化作用机制。项目研究结果将丰富和发展高温合金性能优化及其凝固理论，并为航空发动机关键构件制造的研究和应用提供技术指导。

高温合金具有优异的流动性和力学性能是制造大型薄壁复杂结构铸件的重要性能。然而，由于高温合金凝固温度区间宽，高的粘度以及铸件结构复杂等特点，使得该类铸件良好充型和晶界强化难以协调控制。本项目通过调控高温合金中微量元素硼和锆的含量，实现了在不降低合金力学性能的前提下改善其流动性。结果表明，高温合金中含有适量的硼和锆可同时有效提高合金的流动性和力学性能。随着硼和锆含量增加，合金的流动性先增加后减小。当合金中硼和锆含量较高时，枝晶在糊状区具有较低的生长速率，使得枝晶搭接点温度降低，延缓了枝晶搭接，从而有利于提高熔体流动性。适量的硼和锆可改善晶界特性，延缓裂纹在晶界的形核和扩展，提高了合金的力学性能。通过本项目的研究，明确了合金成分对凝固特性、流动性和力学性能的影响，对航空发动机关键构件用材料的成分优化和制造提供了实验指导和理论依据。