Microstructural evolution and microsegregation in directional solidification of hypoeutectic Al−Cu alloy:A comparison between experimental data and numerical results obtained via phase-field model

定向凝固亚共晶Al−Cu合金显微组织演化和显微偏析:实验数据和相场模拟结果比较

The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field model.The numerical results were compared with experimental data.The experimental values for cooling rates and effective partition coefficient were adopted during calculations.The results of microsegregation through phase-field model show excellent agreement with the experimental data.Such excellent agreement is because cooling rates,effective partition coefficient and back-diffusion of solute are considered in the model.For solidification speed,the calculation results show good agreement with the experimental data.Tertiary dendritic arm spacing calculated with phase-field model is compared with experimental data.The results show good agreement between them.The dendrite arm spacing varies with position because high cooling rates are responsible for the refinement effect on microstructure.Finally,two-dimensional simulation produced a dendrite that is similar to that found in the experiment.

利用相场模型预测Al−Cu合金的显微偏析、凝固速度、枝晶臂间距和枝晶形貌,并将模拟结果与实验结果进行比较。计算中采用冷却速率和有效分配系数的实验值。相场模拟的显微偏析结果与实验值吻合良好,这是由于模型中考虑冷却速率、有效分配系数和溶质的反扩散。凝固速度的计算结果与实验结果吻合较好。将通过相场模型计算的三次枝晶臂间距与实验数据进行比较,两者吻合较好。由于高冷却速率对显微组织的细化作用,枝晶臂间距随位置增大而增大。最后,通过二维模拟得到与实验结果相似的枝晶形貌。