(華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640)
摘 要: 利用Mg-20%Sb中間合金對過共晶Mg-4.8%Si合金進行變質(zhì)處理，考察Sb的含量對Mg2Si初晶變質(zhì)效果(主要包括形態(tài)和尺寸)的影響規(guī)律，并討論其變質(zhì)機制。結(jié)果表明：Sb的加入量是決定其能否有效變質(zhì)過共晶Mg-4.8%Si合金中Mg2Si初晶的重要因素；在未變質(zhì)的過共晶Mg-Si合金中，Mg2Si初晶以粗大的樹枝晶狀為主；當(dāng)Sb加入量低于0.8%(質(zhì)量分?jǐn)?shù))時，Mg2Si初晶形態(tài)無明顯改善，其平均尺寸略有降低；當(dāng)Sb加入量達到并超過1.2%后，Sb才能有效變質(zhì)過共晶Mg-4.8%Si合金中Mg2Si初晶，且Mg2Si初晶呈細(xì)小的顆粒狀彌散分布，其平均尺寸迅速減小；其變質(zhì)機制應(yīng)與殘留在熔體中彌散分布的Mg3Sb2粒子作為Mg2Si初晶的形核核心有關(guān)。
關(guān)鍵字: 過共晶Mg-Si合金；Sb；變質(zhì)；Mg2Si初晶
（School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
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.
Key words: hypereutectic Mg-Si alloy; Sb; modification; primary Mg2Si crystal
