镍基高温合金由于其优异的抗氧化抗腐蚀性能以及良好的组织稳定性，广泛应用于航空航天发动机中涡轮盘等关键热端部件以及超超临界电站的耐热材料。γ'以及γ''相作为镍基高温合金中主要强化相，在合金中发挥重要的强化作用。本工作研究了750 ℃、120 MPa条件下，不同形貌特征的γ'和γ''相强化镍基高温合金的蠕变行为。结果表明，合金中γ'和γ''相尺寸变化会导致蠕变变形行为和蠕变性能的改变。合金析出细小γ'/γ''相时，仅少量位错切入γ'/γ''相，并形成贯穿γ基体和γ'/γ''相的连续层错，合金蠕变性能较差；随着γ'/γ''相尺寸增加，位错易切入γ'相，并在γ'相中形成层错，蠕变性能显著提升；γ'相尺寸继续增大，位错在γ/γ'界面堆积，呈环状包裹γ'相，导致合金蠕变性能降低。晶界附近析出的有害Laves相会弱化晶界；在晶界处析出适量的η/δ相能够提高晶界强度，抑制裂纹扩展，显著提高合金的蠕变寿命；而晶内析出的粗大η/δ相则为裂纹形核提供有利位置，加速合金失效。

Ni-based superalloys have shown great application potential as component materials in aircraft engines because of their excellent mechanical properties at high temperatures. With the development of engine and power plant boiler tubes, the high-temperature creep resistance of nickel-based superalloys has become an important indicator for evaluating the mechanical properties of superalloys. In this study, the creep behavior of the as-cast Ni-based superalloy with the coprecipitation of γ′ and γ″ phases at 750 ^oC and 120 MPa was investigated. The results show that the creep deformation behavior and creep property change with the size of the γ'/γ'' phases. A number of dislocations are cut into the γ'/γ'' phases, forming continuous stacking faults in the γ channel and γ'/γ'' phases when a high amount of compact γ'/γ'' phases are precipitated, leading a inferior creep property. Increasing the size of the γ'/γ'' phases, the dislocations are easily cut in the γ′ phase and isolated stacking faults are formed in the γ′ phase, which significantly enhances the creep property. Further increasing the size of the γ′ phase, the dislocations are piled up on the interface of the γ/γ′ phases, and the γ′ phase is looped with dislocations, which decreases the creep property. Given the precipitation of the deleterious Laves phases, the grain boundaries (GBs) are weakened. However, the stretch of cracks is restrained, and the creep properties of the alloy are enhanced because of the moderate needle-like η/δ phases in the GBs. The precipitation of the overdose η/δ phases provides a favorable location for crack nucleation and accelerates alloy failure.