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利用Mg-20%Ca中间合金对过共晶Mg-Si合金材料进行变质处理,研究了Ca加入量对Mg2Si初晶变质效果的影响规律,并讨论其变质机理。研究结果表明:Ca可有效变质过共晶Mg-Si合金中的Mg2Si初晶。随着Ca含量的增加,Mg2Si初晶形态由粗大树枝状晶、细小树枝晶、非规则外形颗粒到规则外形逐渐过渡。当Ca百分含量达到1.2%时,Mg2Si初晶主要呈现为规则外形。其变质机理应主要与碱土金属富集于Mg2Si相生长表面并抑制优先生长晶向有关。
The Mg-20% Ca master alloy was used to modify the hypereutectic Mg-Si alloy, and the effect of Ca addition on the metamorphism of Mg2Si primary crystal was studied. The metamorphic mechanism was also discussed. The results show that Ca effectively degenerates Mg2Si primary crystal in eutectic Mg-Si alloy. With the increase of Ca content, the morphology of Mg2Si primary crystals gradually changes from coarse dendrite, fine dendrites and irregular shape particles to regular shape. When Ca content reaches 1.2%, Mg2Si primary crystal mainly presents as regular shape. The metamorphic mechanism should mainly be related to the enrichment of alkaline earth metal on the growth surface of Mg2Si phase and inhibition of the preferential growth direction.