Fe-Ni基奥氏体合金焊件时效过程中沉淀相γ′异步长大及γ′/γ界面演变机理

γ′[Ni3(Ti,Al)]沉淀相共格强化Fe-Ni基奥氏体合金兼具较高强度和较好的抗氢脆性能，是诸多关键领域的理想临氢服役结构材料。然而，焊缝作为整个工件的强度薄弱区降低了其服役许用应力及寿命。前期研究表明焊缝中γ′相的粗化及 γ′/γ的半共格相界面协同作用改变了位错与γ′相的作用方式，进而降低了焊缝强度，但关于焊缝中γ′相的粗化及γ′/γ界面的失配机理尚不清楚。本申请拟结合扫描电镜微结构分析、电子探针成分偏聚表征、热脱附空位浓度测量、透射电镜γ′/γ相界面分析等手段着重研究：(1) 时效前焊件内成分分布及空位浓度对γ′相析出长大的影响机制；(2) 焊件内γ′相长大过程中γ′/γ界面的演变机制。综合以上两方面研究揭示时效过程中焊件内γ′相的异步长大、γ′/γ界面状态的演变机制，为Fe-Ni基沉淀强化奥氏体合金焊件的性能调控奠定理论基础，也为其他新型共格沉淀强化合金的焊接提供借鉴。

γ′[Ni3(Ti,Al)] precipitates play an essential role in strengthening the Fe-Ni austenite alloys for critical structure application in hydrogen environment. The weldment, being a relatively soft region in a large-scale application of these alloys, significantly attenuates the allowed strength and lifetime of the structure. Prior investigations indicate that coarsening of the γ′ precipitates and semi-coherent nature of the γ′/ γ interface synergistically changed the interplay between dislocation slip and the γ′ precipitates, and consequently reduced the weldment strength. However, the mechanisms of γ′ precipitate coarsening and γ′/ γ interface evolution during the aging treatment remains elusive to date, which are the fundamental basis for the proper control of the weldment. Here, by analyzing the microstructure, elements segregation, vacancy concentration and atomic structure of the γ′/ γ interface in the weldment using scanning electron microscopy, electron probe, thermo-desorption spectroscopy and transmission electron microscopy, we will investigate (1) the role of elements distribution and vacancy concentration in the weldment before aging treatment in γ′ precipitates coarsening; (2) γ′/ γ interface evolution with the γ′ growth during aging treatment. These studies will elucidate the γ′ coarsening mechanism and γ′/ γ interface evolution during aging treatment of the weldment, laying a theoretical foundation for optimizing the properties of Fe-Ni austenite alloys weldment and providing insights for the treatment of the weld in other novel coherent-precipitation hardening alloys.