强磁场下过共晶铝硅合金凝固过程中初晶硅的迁移行为

研究了在磁场梯度约为25T/m条件下不同磁场强度以及磁场强度约为5T时不同磁场梯度对半熔态Al-18Si合金凝固过程中初晶硅迁移行为的影响。结果表明:当磁场强度大于2.3T时,初晶硅开始迁移,但没有偏聚;当磁场强度达到6.6T时,初晶硅发生迁移并聚集,产生明显的聚集层;且随着磁场强度的进一步增大(磁场强度分别增至7.7和9.9T),聚集层的厚度基本保持不变;当磁场强度不变,随着磁场梯度的增大,初晶硅的偏聚量增加,晶粒尺寸变小。并对磁场强度影响初晶硅迁移的机制进行了探讨。

Migratory behaviors of primary crystal silicon in hypereutectic Al-Si alloy under high magnetic field

The migration behaviors of the primary Si grains during solidification of Al-18Si alloy from mushy zone was investigated under various magnetic flux density and gradient.The effects of magnetic flux on the migration were investigated when the magnetic field gradient was set at 25 T/m,the effects of the field gradient was investigated when the flux density was set at 5 T.The results show that the migration behaviors of the primary Si grains do not take place until the magnetic flux density is over 2.3 T.The primary Si grains tend to migrate and form a remarkable Si-rich layer at magnetic flux of 6.6 T.The thickness of Si-rich layer is almost unchanged with further increase of magnetic flux density.The amount of segregated primary silicon grains increases with increasing magnetic gradient,whereas the grain size decreases.The mechanism of influence of the magnetic flux density on the migratory behavior was discussed.