Grain refinement of hypoeutectic Al-Si alloys with B

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• 作者：Zongning Chen^a ; ^b ; Huijun Kang^a ; ^c ; Guohua Fan^d ; Jiehua Li^e ; Yiping Lu^a ; Jinchuan Jie^a ; Yubo Zhang^a ; Tingju Li^a ; Xigao Jian^b ; Tongmin Wang^a ; ^{tmwang@dlut.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Grain refinement ; Al-Si alloys ; Nucleation ; Edge-to-edge matching model
• 刊名：Acta Materialia
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：120
• 期：Complete
• 页码：168-178
• 全文大小：4748 K

文摘

The enhanced grain refining efficiency of B in treating hypoeutectic Al-Si alloys has been identified for more than 30 years. However, its exact underlying mechanism remains to be explored. Here, we report that AlB₂ could be a highly efficient nucleating substrate for α-Al in Al-Si alloys with high Si concentrations. The addition of AlB₂ alone without the presence of Si does not result in a significant grain refinement. The enhanced grain refining efficiency can be mainly attributed to the enhanced heterogeneous nucleation of AlB₂ caused by Si. It is proposed that the creation of a layer of SiB₆ at the interface between AlB₂ and Al may reduce the crystallographic mismatch, which can significantly improve the nucleating potency of AlB₂. Furthermore, the formation of SiB₆ layer may occur for only a limited span of time in Al-Si melt, and it may further transform to other stable phase (e.g. Si). This investigation reveals the nucleating behavior of AlB₂ influenced by solute Si and thereby sheds some novel insights on the grain refinement mechanism of Al alloy.