A model of discontinuous precipitation of γ′ phase at grain boundaries (GBs) in polycrystalline Ni-based superalloys during continuous cooling from supersolvus temperature was developed. The model calculates the size and γ′ phase fraction in GB precipitates as a function of cooling rate and GB mobility. The model is based on the classical mechanism of diffusion-controlled precipitation. It considers fast diffusion of γ′-forming elements along the GB and the motion of the GBs under driving force induced by alloy decomposition. The model predicts either discrete GB gamma-prime particles and GB serration or the growth of fan-type structures depending on the cooling rate and GB mobility. We conclude from the model predictions that the GB mobility is the key factor controlling the type and morphology of GB precipitates. High GB mobility results in formation of fan-type structures, while the lower GB mobility leads to GB serration. The predicted dependence of the size of GB precipitates on the cooling rate is in good agreement with the experimental observations.

建立了从超固溶温度连续冷却过程中，多晶Ni基高温合金中γ '相在晶界（GBs）处的不连续析出模型。该模型根据冷却速率和GB迁移率计算GB沉淀物中的尺寸和γ ′相分数。该模型基于扩散控制降水的经典机制。考虑γ的快速扩散沿GB的'形成元素和在合金分解驱动下的GBs运动。该模型根据冷却速率和GB迁移率预测离散的GBγ-prime粒子和GB锯齿或风扇型结构的增长。我们从模型预测中得出结论，GB迁移率是控制GB沉淀物的类型和形态的关键因素。高GB迁移率导致形成扇形结构，而较低GB迁移率导致GB锯齿。GB析出物的大小对冷却速率的预测依赖性与实验观察结果非常吻合。