Ta和Th掺杂对新型γ′强化铱基高温合金的组织演变与强韧化的影响机制

Traditional γ' phase strengthening iridium-based superalloy having excellent high-temperature mechanical and corrosion resistance, particularly suited to the application in the field of aerospace high-temperature resistant, anti-oxidation and anti-corrosion harsh working environment. However, because the strength and toughness of the alloy does not match, which limits its practical application. In recent years, novel ternary γ'-Ir3(Al, W) phase was reported in Ir-Al-W system, which provides a pathway for the development of this new class of iridium-based superalloy..It has been found that γ'-Ir3(Al,W) phase can be further strengthen by addition of Ta, which can effectively improved the high temperature mechanical property of iridium alloy, and the plasticity of alloy can be effectively improved by doping of Th. In the present study, effect of Ta and doping Th elements on the microstructure evolution, high temperature microstructure stability, high temperature compression mechanical behavior, grain boundaries strength and influence of crack initiation expansion will be investigated systematically in the Ir-Al-W based superalloy. Effect of Ta on high temperature stability of γ'-Ir3(Al,W) phase and toughening mechanism of Th elements will be clarified. This project will provide a fundamental understanding and experimental data accumulation for further developing this new generation iridium-based superalloys with higher temperature capability, ideal for two-phase structure and strength and toughness coordination.

传统的γ′相强化铱基高温合金具有优异的高温力学和抗腐蚀性能，特别适合于航天航空领域中要求耐超高温、抗氧化和抗腐蚀的工作环境，但由于合金强韧性不匹配，限制了其实际应用。近年来，在Ir-Al-W合金体系中发现的新型三元γ′-Ir3(Al,W)相将有可能改变这种现状，为开发下一代新型铱基高温合金提供了一条新的道路。.已有研究发现，Ta元素能进一步强化Ir-Al-W合金中的γ′-Ir3(Al,W)相，Th元素掺杂能有效改善铱合金的高低温塑性。因此，本项目以Ir-Al-W高温合金为研究对象，从合金元素成分分配比出发，系统研究Ta和掺杂Th元素对合金组织结构、高温组织稳定性、高温压缩力学行为、晶界强度和裂纹萌生扩展的影响规律，阐明Ta显著提高γ'相高温稳定性的强化机理及Th元素增加晶界强度的韧化机制等两个关键科学问题，为发展更高承温能力、两相组织和强韧性匹配的新一代铱基高温合金提供理论基础和实验数据。

Ir基超高温合金在航空航天、深空探测及医学领域有重要应用价值和发展潜力。本项目以新型γ+γ’两相Ir基合金为研究对象，基于成分设计添加Al、W、Ta、Th元素进行合金化，研究合金中γ相、γ’相、β相的形成及组织演化和力学性能，主要研究结果如下：① 阐明了不同Al、W配比下组织中γ和γ’相的演化规律，分析了基体相和强化相体积分数、形貌特征及成分分布；② 研究了不同Ta和微量Th元素添加下的Ir-6Al-13W-(Ta, Th)合金组织演变规律，分析了Ta和Th元素对γ和γ’相形成的作用机制，以及元素分布特征，对探索了Ta元素对γ’相的稳定性，以及热处理后的组织演变特点；③评估分析了γ+γ’两相Ir-Al-W-(Ta, Th)合金的室温及高温力学性能，讨论了γ和γ’相在高温压缩下的演化行为，拓展研究了多晶Ir的高温变形及断裂模式，以及不同取向Ir单晶的微纳力学性能。研究结果对Ir基超高温合金的成分设计、组织及性能优化具有重要科学指导意义。