Sb对过共晶Mg-4.8%Si合金中Mg₂Si初晶变质的影响

来源期刊：中国有色金属学报2010年第1期

论文作者：郭小宏 杜军 李文芳 彭继华

文章页码：24 - 29

关键词：过共晶Mg-Si合金；Sb；变质；Mg₂Si初晶,hypereutectic Mg-Si alloy; Sb; modification; primary Mg₂Si crystal

Key words：hypereutectic Mg-Si alloy; Sb; modification; primary Mg₂Si crystal

摘    要：利用Mg-20%Sb中间合金对过共晶Mg-4.8%Si合金进行变质处理，考察Sb的含量对Mg₂Si初晶变质效果(主要包括形态和尺寸)的影响规律，并讨论其变质机制。结果表明：Sb的加入量是决定其能否有效变质过共晶Mg-4.8%Si合金中Mg₂Si初晶的重要因素；在未变质的过共晶Mg-Si合金中，Mg₂Si初晶以粗大的树枝晶状为主；当Sb加入量低于0.8%(质量分数)时，Mg₂Si初晶形态无明显改善，其平均尺寸略有降低；当Sb加入量达到并超过1.2%后，Sb才能有效变质过共晶Mg-4.8%Si合金中Mg₂Si初晶，且Mg₂Si初晶呈细小的颗粒状弥散分布，其平均尺寸迅速减小；其变质机制应与残留在熔体中弥散分布的Mg₃Sb₂粒子作为Mg₂Si初晶的形核核心有关。

Abstract: The hypereutectic Mg-4.8%Si alloy was modified by using Mg-20%Sb master alloy. The effect of Sb addition on the modification of primary Mg₂Si crystals and its modification mechanism were investigated. The results show that the Sb content is a significant factor that determines the modification effect of primary Mg₂Si crystals. The primary Mg₂Si crystals are mainly coarse dendritic for the unmodified hypereutectic Mg-4.8%Si alloy. The morphologies of primary Mg₂Si crystals can not be effectively modified by Sb under the condition of Sb content less than 0.8%. The average sizes of primary Mg₂Si crystals slightly decrease. With the Sb addition increasing to 1.2%, the primary Mg₂Si crystals are effectively modified into small particles, which distribute uniformly. Compared with the unmodified hypereutectic Mg-4.8%Si alloy, the average sizes of the primary Mg₂Si crystals for the modified Mg-4.8%Si alloy by 1.2%Sb addition drastically decrease. The modification mechanism should be associated with the Mg₃Sb₂ particles remained in the hypereutectic Mg-4.8%Si meld modified by Mg-20%Sb master alloy. The Mg₃Sb₂ particles should act as nucleating substrates of the primary Mg₂Si crystals during solidification.

基金信息：广东省自然科学基金资助项目