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针对Al-11.6％Si和Al-11.6％Si-0.4％Mg两种近共晶成分铸造合金,考察了Sr的加入对组织中α枝晶形态的影响,测量了完全变质合金中α枝晶相数量及α枝晶的特征参数:一次分枝间距和二次枝臂间距.结果表明,Sr的加入促进了α枝晶柱状化生长并导致α枝晶相数量大幅度提高;在完全变质合金中,随着合金中Sr量增加.一次分枝间距和二次枝臂间距都降低,Sr对α枝晶起一定的细化作用.Sr加入到Al-Si合金中引起合金液的性质发生了显著变化,Sr的存在降低了α枝晶固液界面能,导致枝晶尖端的生长过冷度降低,抑制液相中等轴晶的形核,因此Sr的加入促进了柱状枝晶的形成.固液界面能的降低也使得柱状枝晶的二次枝臂间距和一次分枝间距随着Sr量增多而降低.
Al-11.6% Si and Al-11.6% Si-0.4% Mg two kinds of near-eutectic composition of cast alloy, investigated the addition of Sr on the morphology of α dendrites in the organization, measured the fully degenerate alloy α dendrite phase The results showed that the addition of Sr promoted the dendritic growth of α dendrites and led to a substantial increase in the number of α dendrites. In the fully metamorphic alloys , With the increase of Sr content in the alloy, the primary and secondary branch arm spacing are decreased, Sr refinement effect on the α dendrite.Sr added to the Al-Si alloy caused the nature of the alloy liquid occurred significantly , The presence of Sr lowers the interfacial energy of α-dendritic solid-liquid, resulting in the decrease of undercooling at the tip of dendrite and inhibiting the nucleation of equiaxed crystals in the liquid phase. Therefore, the addition of Sr promotes the formation of columnar dendrites. The reduction of interfacial energy also makes the secondary branch arm spacing and the first branch spacing of column dendrites decrease with the increase of Sr content.