He Min, Zhang Zhifeng, Mao Weimin, Li Bao, Bai Yuelong, Xu Jun
General Research Institute for Non-ferrous Metals, Beijing 100088, China.
School of Materials and Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Materials (Basel). 2019 Mar 11;12(5):820. doi: 10.3390/ma12050820.
This study presents a modified annular electromagnetic stirring (M-AEMS) melt treatment suitable for a large-volume and high-alloyed aluminum alloy. A 3D computational model coupling an electromagnetic model with a macroscopic heat and fluid-flow model was established by using Ansoft Maxwell 3D and Fluent from ANSYS workbench, and the effects of the electromagnetic shielding ring, the height of the magnet yoke, the shape of the iron core, and the internal cooling mandrel on the electromagnetic, thermal and flow fields were studied numerically. Based on the optimal technical parameters, the effectivity of the M-AEMS process by using 7075 alloy was validated experimentally. The results show that a favorable electromagnetic field distribution can be achieved by changing the magnet yoke height, the iron-core shape and the electromagnetic shielding ring, and the melt temperature of the 7075 alloy can drop rapidly to the pouring temperature by imposing the internal cooling mandrel; compared with ordinary annular electromagnetic stirring, the M-AEMS process creates a lower magnetic strength near the melt top, beneficial for stabilizing the melt surface; meanwhile, it yields a higher magnetic strength near the melt bottom, which increases the shear rate and ensures an optimal stirring effect. Therefore, M-AEMS works more efficiently because the thermal and composition fields become uniform in a shorter time, which reduces the average grain size and the composition segregation, and a more stable melt surface can be obtained during treatment, which reduces the number of air and oxide inclusions in the melt.
本研究提出了一种适用于大体积、高合金化铝合金的改进型环形电磁搅拌（M-AEMS）熔体处理方法。利用ANSYS workbench中的Ansoft Maxwell 3D和Fluent建立了一个将电磁模型与宏观热流和流体流动模型耦合的三维计算模型，并数值研究了电磁屏蔽环、磁轭高度、铁芯形状和内部冷却芯轴对电磁场、热场和流场的影响。基于优化后的工艺参数，通过实验验证了采用7075合金的M-AEMS工艺的有效性。结果表明，通过改变磁轭高度、铁芯形状和电磁屏蔽环可以实现良好的电磁场分布，通过设置内部冷却芯轴，7075合金的熔体温度可以迅速降至浇注温度；与普通环形电磁搅拌相比，M-AEMS工艺在熔体顶部附近产生较低的磁场强度，有利于稳定熔体表面；同时，它在熔体底部附近产生较高的磁场强度，这增加了剪切速率并确保了最佳搅拌效果。因此，M-AEMS工作效率更高，因为热场和成分场在更短的时间内变得均匀，这减小了平均晶粒尺寸并减少了成分偏析，并且在处理过程中可以获得更稳定的熔体表面，这减少了熔体中空气和氧化物夹杂的数量。
