强磁场对Al-Si合金凝固组织中硅分布的影响

为了揭示强磁场对金属凝固组织的影响规律，本文研究了Al-14.98%Si(质量分数)和Al-9.2%Si(质量分数)合金在强磁场作用下凝固组织的变化趋势，分析了强磁场对合金凝固组织中Si分布的影响.研究发现，均恒磁场和梯度磁场分别通过洛伦兹力和磁化力的作用对合金的凝固组织产生影响，强磁场可以显著改变初晶硅在合金中的分布状况.在均恒磁场作用条件下初晶硅在合金中均匀分布；在梯度磁场条件下，由于磁化力和浮力的共同作用，初晶硅在试样的上部或下部聚集.同时，磁化力也改变了共晶体在合金中的组织形态，使试样上部和下部共晶体的层片间距明显不同.理论和实验分析表明，Al-Si合金在强磁场中凝固时，磁场能作用于凝固过程，使共晶体中的Al含量增大，共晶点向左偏移.关键词：强磁场凝固过程共晶组织Al-Si合金

Effects of high magnetic fields on the distribution of Si in solidified structures of Al-Si alloy

In order to find the effects of high magnetic fields on the solidification processes of metallic materials, the changes of solidified structures of Al-14.98% Si and Al-9.2% Si alloys were examined in this study. The alloys were solidified under different magnetic field conditions, and then the distribution and morphologies of Si element in the solidified structures was analyzed. It is found that uniform magnetic fields and gradient magnetic fields can affect the solidified structures of the alloy by Lorenz force and magnetization force respectively, and the imposed magnetic fields also can change the distribution of primary Si crystals in the alloy remarkably. The primary Si crystals distributed homogeneously under uniform magnetic field conditions, while they congregated at the upside or downside of samples by the combined action of buoyancy and magnetization force under gradient magnetic field conditions. Furthermore, the morphologies of eutectic crystals in the alloy were changed by the magnetic fields and the layer thickness of eutectic crystals were different at the upside and downside under gradient magnetic field. Both theoretical analysis and examinations indicated that magnetic energy also affected the solidifying process, the content of eutectic aluminum in eutectic structure increased and eutectic point left-shifted when Al-Si alloy solidified under high magnetic fields.