脉冲磁致振荡下纯铝凝固磁场与流场分布的数值模拟

摘要

The metal grain can be refined under pulse magneto-oscillation (PMO). In order to study its mechanism, the numerical simulation of the magnetic field and flow field distributions during pure aluminum solidification under PMO has been carried out with ANSYS. Because of the skin effect, the pulse current in the coil generates electromagnetic force in the surface melt. The magnetic pulling and pressure force can be generated alternatively, and in radial direction, the magnetic force appears with direction to top and bottom in turn. The free nucleus separated from the melt surface will be oscillated to drift away to increase the nucleation rate. Meanwhile the melt is forced to flow, which is beneficial to the uniform distribution of the nucleus, the temperature field and the concentration field.%脉冲磁致振荡可以细化金属晶粒,为了研究其作用机理,采用ANSYS有限元模拟软件对脉冲磁致振荡下纯铝凝固磁场与流场分布进行了数值模拟.模拟结果显示,由于电磁趋肤效应,线圈中脉冲电流只在熔体表面感应产生电磁力,且随时间出现指向内部的压力与指向外部的拉力交替变化,沿径向有指向熔体顶部与底部交替变化.交变电磁力可以振荡熔体表面率先析出的晶核而使之游离,增大熔体形核率.同时感应电磁力迫使熔体产生流动,会利于晶核的均匀分布与温度场、浓度场的均匀化.