Xu Ruida, Li Ying, Yu Huichen
Science and Technology on Advanced High Temperature Structure Materials Laboratory, AECC Key Laboratory of Aeronautical Materials Testing and Evaluation, Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation, Beijing Institute of Aeronautical Materials, Beijing 100095, China.
Materials (Basel). 2023 Jul 22;16(14):5166. doi: 10.3390/ma16145166.
The present study investigates the creep behavior and deformation mechanism of a third-generation single-crystal Ni-based superalloy at 1170 °C under a range of stress levels. Scanning electron microscopes (SEM) and transmission electron microscopes (TEM) were employed to observe the formation of a rafted γ' phase, which exhibits a topologically close-packed (TCP) structure. The orientation relationship and elemental composition of the TCP phase and matrix were analyzed to discern their impact on the creep properties of the alloy. The primary deformation mechanism of the examined alloy was identified as dislocation slipping within the γ matrix, accompanied by the climbing of dislocations over the rafted γ' phase during the initial stage of creep. In the later stages of creep, super-dislocations with Burgers vectors of a<010> and a/2<110> were observed to shear into the γ' phase, originating from interfacial dislocation networks. Up to the fracture, the sequential activation of dislocation shearing in the primary and secondary slipping systems of the γ' phase occurs. As a consequence of this alternating dislocation shearing, a twist deformation of the rafted γ' phase ensued, ultimately contributing to the fracture mechanism observed in the alloy during creep.
本研究调查了第三代单晶镍基高温合金在1170°C和一系列应力水平下的蠕变行为及变形机制。使用扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察筏状γ'相的形成，该相呈现拓扑密排（TCP）结构。分析了TCP相和基体的取向关系及元素组成，以了解它们对合金蠕变性能的影响。研究发现，所研究合金的主要变形机制为γ基体中的位错滑移，在蠕变初始阶段还伴有位错在筏状γ'相上的攀移。在蠕变后期，观察到柏氏矢量为a<010>和a/2<110>的超位错从界面位错网络切入γ'相。直至断裂，γ'相的主、次滑移系统中依次发生位错切变激活。这种交替的位错切变导致筏状γ'相发生扭曲变形，最终促成了合金在蠕变过程中观察到的断裂机制。
