The microstructure evolution of Ni-based superalloys during heat treatment is of great significance for obtaining better service performance. However, heat treatment experimentation is costly and time-consuming, and sometimes fails to reveal physical mechanisms well. In the present study, a multiphase-field model coupled with an explicit nucleation algorithm was established to simulate the precipitation and growth of γ¢ phase in DD6 superalloy, which can be applied to a multicomponent elastic-inhomogeneous system. The PanNickel^© database was used to calculate thermodynamic and kinetic data in multicomponent superalloys. First, the coupling method of multiphase-field model and explicit nucleation algorithm was introduced. The coupled model was used to simulate the precipitation of γ¢ phase under isothermal and non-isothermal conditions. It was found that a unimodal microstructure was formed under isothermal conditions and there was a “soft impingement” phenomenon, while a bimodal distribution composed of cuboidal γ¢ precipitates and fine secondary γ¢ precipitates was formed during a cooling process of 25-125 °C/min. The effect of cooling rate was studied. Then, the chemical and elastic driving forces were analyzed. It was found that Al and Ta contributed most to the chemical driving force, while Re and W gathered at the γ/γ¢ interface and inhibited the growth of γ¢ phase. γ¢ precipitates had a cuboidal shape under the influence of elastic driving force. Finally, the growth and coarsening process of γ¢ phase was studied and compared with the well-known Lifshitz-Slyosov-Wagner (LSW) theory. The growth of γ¢ phase can be divided into rapid growth, coarsening and quasi-static coarsening stages according to the simulation results, among which the coarsening stage is basically consistent with the LSW theory. The current model can be used to simulate the precipitation and growth of single crystal superalloys where multicomponent and elastic effects are considered.

中文翻译：

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多相场法和显式成核算法模拟单晶高温合金DD6中γ¢相的析出和生长模拟

镍基高温合金在热处理过程中的组织演变对获得更好的服务性能具有重要意义。然而，热处理实验是昂贵且费时的，并且有时不能很好地揭示物理机制。在本研究中，建立了一个多相场模型和一个显式成核算法，以模拟DD6合金中γ¢相的析出和生长，该模型可应用于多组分弹性非均质体系。PanNickel ^©数据库用于计算多组分高温合金的热力学和动力学数据。首先，介绍了多相场模型与显式成核算法的耦合方法。耦合模型用于模拟等温和非等温条件下γ¢相的析出。发现在25-125°C的冷却过程中，等温条件下形成了单峰微观结构，并出现“软碰撞”现象，而长方体γ¢析出物和细小的次级γ¢析出物形成了双峰分布。 /分钟。研究了冷却速率的影响。然后，分析了化学和弹性驱动力。发现Al和Ta对化学驱动力的贡献最大，而Re和W聚集在γ/γ¢界面上并抑制了γ¢相的生长。γ¢沉淀物在弹性驱动力的作用下呈长方体形状。最后，研究了γ¢相的生长和粗化过程，并与著名的Lifshitz-Slyosov-Wagner（LSW）理论进行了比较。根据模拟结果，γ¢相的生长可分为快速生长，粗化和准静态粗化阶段，其中粗化阶段与LSW理论基本一致。当前模型可用于模拟考虑了多组分和弹性效应的单晶高温合金的沉淀和生长。根据模拟结果，γ¢相的生长可分为快速生长，粗化和准静态粗化阶段，其中粗化阶段与LSW理论基本一致。当前模型可用于模拟考虑了多组分和弹性效应的单晶高温合金的沉淀和生长。根据模拟结果，γ¢相的生长可分为快速生长，粗化和准静态粗化阶段，其中粗化阶段与LSW理论基本一致。当前模型可用于模拟考虑了多组分和弹性效应的单晶高温合金的沉淀和生长。