定向凝固过程中镍基高温合金铸件的枝晶生长模拟（英文）

提高铸件的性能需要对其凝固过程中枝晶的生长深入了解,为此,采用数值模拟方法对定向凝固(DS)过程中枝晶的生长进行详细研究。考虑溶质扩散并耦合宏观温度场建立预测枝晶生长的多尺度模型。采用定向凝固实验验证模型的准确性,冷却曲线以及晶粒形貌的实验结果和模拟结果吻合较好。采用所建立的模型模拟枝晶的竞争生长,讨论分析具有不同结晶取向角枝晶的竞争生长行为。随后,采用模拟和实验的方法对三维枝晶的生长进行研究,模拟和实验结果吻合较好。通过3个不同的算例研究初始形核数对枝晶生长的影响。研究表明:初始形核数对柱状晶起始阶段的生长影响较大,对铸件最终的枝晶形貌和一次枝晶臂间距(PDAS)影响较小。

Numerical simulation of dendrite growth in Ni-based superalloy casting during directional solidification process

An understanding of dendrite growth is required in order to improve the properties of castings. For this reason, cellular automaton-finite difference(CA-FD) method was used to investigate the dendrite growth during directional solidification(DS)process. The solute diffusion model combined with macro temperature field model was established for predicting the dendrite growth behavior. Model validation was performed by the DS experiment, and the cooling curves and grain structures obtained by the experiment presented a reasonable agreement with the simulation results. The competitive growth of dendrites was also simulated by the proposed model, and the competitive behavior of dendrites with different misalignment angles was also discussed in detail.Subsequently, 3D dendrites growth was also investigated by experiment and simulation, and both were in good accordance. The influence on dendrites growth of initial nucleus was investigated by three simulation cases, and the results showed that the initial nuclei just had an effect on the initial growth stage of columnar dendrites, but had little influence on the final dendritic morphology and the primary dendrite arm spacing.