Abstract
• The effect of strong convection on the distribution of the ZrB 2 phase is revealed. • The influence of Zr-rich particle on the impurity contents in primary Si is analyzed. • The B content of the Si-rich areas in the sample presents a gradient distribution. The effect of migration behavior of the impurity phases on the Al-30wt.%Si solvent refining during the electromagnetic directional solidification process was investigated. The simulation shows that there is a strong convection inside the melt, and it weakens with the pull-down process of the samples. Because the nucleation and growth temperature of the ZrB 2 phase is higher than that of the primary Si, the strong convection in the melt results in a distribution of the ZrB 2 phase at the top and the bottom of the sample. With the excessive Zr addition, the ZrSi 2 phase, whose growth temperature range is between the liquidus and the eutectic point, mainly appears in the Si-rich area. The distribution position of the two Zr-rich phases in the sample is affected by different factors (flow field and temperature gradient), which has a great influence on the impurity contents in the primary Si. Separate tests on different areas of the Si-rich part in the samples show that the B content in the different areas presents a gradient distribution, and the B content of the upper part is obviously lower than that of the bottom part. This study provides a new idea for improving the control of the impurity phase distribution during the directional solidification of Al-Si solvent refining.
Published Version
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