复合磁场对金属熔体流动及凝固组织的影响

Flow and Solidification Microstructure in Metal Melts Driven by a Combined Magnetic Field

近年来,复合电磁场作用下的合金凝固组织得到了相当大的关注。本工作以Ga-20%In-12%Sn和Al-7%Si(质量分数)合金为研究对象,研究了脉冲磁致振荡(PMO)与静磁场形成的复合磁场(CMF)对金属熔体流动和Al-7%Si合金凝固组织的影响规律。数值模拟和流动实验结果表明,CMF作用下平行于静磁场方向流型为单环流,垂直于静磁场方向流型为双环流,这与PMO单独作用下熔体流型为双环流有所不同。通过数值模拟CMF作用下金属熔体中电磁力分布和演变结果给出了其流型形成的原因。此外,凝固实验结果表明,本实验参数下CMF处理后的Al-7%Si合金晶粒尺寸小于仅单独施加PMO时所得晶粒尺寸。最后,在现有电磁场作用下金属凝固细晶机制的基础上,结合感应电流、电磁力和强制流动等效应对其凝固细晶机制进行了探讨。

In recent years,solidified structures in metal alloys driven by combined electromagnetic fields have received considerable attention.In this study,the effect of combined magnetic field(CMF)formed by pulsed magneto oscillation(PMO)and static magnetic field on the melt flow of Ga-20%In-12%Sn(mass fraction)and solidification structure of Al-7%Si alloy was investigated.Results of numerical simulations and flow experiments show that the flow pattern is single rolled in the direction parallel to the static magnetic field and double rolled in the direction perpendicular to the static magnetic field,which is different from the double-rolled flow pattern of the melt when the PMO is activated alone.The distribution and evolution of the electromagnetic forces in the melt under CMF are numerically simulated to explain the formation of the flow pattern.Moreover,the experimental results of solidification show that the grain size of the CMF-treated Al-7%Si alloy is smaller than that obtained when PMO is applied.Finally,the grain refinement mechanism of the Al-7%Si alloy under the influence of electromagnetic fields is discussed in relation to the effects of induced currents,electromagnetic forces,and forced flow based on the previously proposed mechanism of grain refinement in solidified metals driven by electromagnetic fields.