铝合金铸件定向凝固过程的数值模拟

为了研究铝合金定向凝固组织的变化规律，采用有限元软件ProCAST对Al Si Cu合金定向凝固过程进行模拟,分析了不同浇注温度和抽拉速率对铸件定向凝固过程中的温度梯度、固液界面前沿、糊状区宽度、枝晶生长速率和二次枝晶臂间距的影响。结果表明，当浇注温度越高时，温度梯度越大，而固液界面前沿下凹越小，糊状区宽度也越窄，从而越有利于顺序凝固的发生；随着抽拉速率的增大，枝晶生长速率先增大后减小,当抽拉速率为200 μm/s时，最大生长速度达到0.093 mm/s，铸件凝固组织最佳；当抽拉速率大于300或小于200 μm/s时，都会导致枝晶生长速率缓慢，枝晶生长不平稳，二次枝晶臂粗大。对模拟得到较优的工艺参数进行试验验证，可以制备出具有较好力学性能的铸件。

Numerical simulation of directional solidification process of aluminum alloy casting

In order to study the change rule of directional solidification microstructure of aluminum alloy, the directional solidification process of Al Si Cu aluminum alloy was simulated with the finite element simulation software ProCAST. The effects of different pouring temperature and pulling rate on the temperature gradient, solid liquid interface front, the width of the mushy zone, dendritic growth rate and secondary dendritic arm spacing during directional solidification of castings were simulated and analyzed. The results showed that the higher the pouring temperature, the greater the temperature gradient, and the smaller the concave at the front of the solid liquid interface, the narrower the width of the mushy zone. Which was more favorable for sequential solidification. With the increase of pulling rate, the dendritic growth rate first increased and then decreased. When the pulling rate was 200 μm/s and the maximum dendritic growth rate was 0.093 mm/s, the solidification structure of the casting was the best. When the pulling rate was greater than 300 μm/s or less than 200 μm/s, the dendritic growth rate would be slow, the dendritic growth would not be stable, and the secondary dendritic arm would be coarse. The better process parameters obtained by simulation were verified by testing, which could be used to prepare castings with better mechanical properties.