(南昌大學 機電工程學院，南昌 330031)
摘 要: 采用OM、SEM、EDS、XRD等研究復合變質(zhì)劑組成對AZ91D鎂合金鑄態(tài)和固溶態(tài)組織的影響，并分析晶粒細化作用機理。結(jié)果表明，適當加入三元復合碳變質(zhì)劑可使AZ91D鎂合金的晶粒尺寸顯著減小，在相同的實驗條件下，當3種碳化物組分MgCO3、SiC、C2Cl6的質(zhì)量比為3:1:1時，能夠獲得最好的細化效果。一方面，MgCO3、C2Cl6在熔體中分解出的C與Al發(fā)生原位反應，生成的大量Al4C3顆粒均勻分散到熔體中，直接成為α-Mg的形核核心；另一方面，在α-Mg晶體生長過程中部分細小的Al4C3顆粒與SiC顆粒一起被固液界面推移至晶界，起到阻礙晶體長大作用，使α-Mg晶粒得到有效細化。
關(guān)鍵字: AZ91D鎂合金；復合變質(zhì)劑；Al4C3；晶粒細化
（School of Mechanical and Electrical Engineering, Nanchang University, Nanchang 330031, China）
Abstract:The effects of complex inoculants on the as-cast and solid-solution state microstructure of AZ91D magnesium alloy and the grain refinement mechanism were investigated by OM, SEM, EDS and XRD. The results show that the grain size of AZ91D magnesium alloy decreases effectively after the complex carbon inoculants are added. The best refinement result can be achieved when the mass ratio of MgCO3, C2Cl6 and SiC is set as 3:1:1. On one hand, the amount of Al4C3 particles induced by carbon-containing compound including MgCO3 and C2Cl6 can directly serve as the heterogeneous nucleus of primary α-Mg phase. On the other hand, some of the fine Al4C3 and SiC particles are pushed by solid-liquid interface between α-Mg phases and the melt, and distribute along the crystal boundary, so as to impede the growth of α-Mg grains, and the α-Mg grains are greatly refined finally.
Key words: AZ91D magnesium alloy; complex inoculants; Al4C3; grain refinement
