使用SO2／Air／N2气氛作为纯Mg及AZ91D合金的熔炼保护  

USE OF SO_2/Air/N_2 COVER GASES FOR THE PROTECTION ON MOLTEN MAGNESIUM AND AZ91D ALLOY

作　　者：王先飞[1] 熊守美[1] 

机构地区：[1]清华大学材料学院,清华大学汽车安全与节能国家重点实验室,北京100084

出　　处：《金属学报》2014年第1期32-40,共9页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51275269;国家科技支撑计划重点项目2011BAE22B02;科技部国际科技合作计划项目2010DFA72760资助~~

摘　　要：利用3种实验方法,研究了SO_2/Air/N_2气氛对纯Mg及AZ91D合金熔体的保护行为,运用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)、Auger电子能谱仪(AES)和X射线光电子能谱仪(XPS)分析了形成的表面膜的相组成、微观组织形貌和生长过程,结合热力学计算讨论了表面膜的生长与保护机理,并考查了表面膜的稳定性.研究表明:在SO_2/Air/N_2气氛中,保护性表面膜由MgO,MgS和MgSO_4混合组成,MgSO_4是热力学稳定相,它的形成至关重要.当采用SO_2/Air/N_2气氛为保护气氛且SO_2含量一定时,Air含量不能过高也不能过低.Molten magnesium and AZ91D alloy oxidize rapidly during casting process, sulfur dioxide （SO2） mixed with carrier gases can be used to protect the melt by reacting with the melt to form a coherent protective film on the melt surface. In this work, the films formed in SOJAir/N2 cover gases were characterized by X-ray diffrac- tion （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, Auger electron spectros- copy （AES） and X-ray photoelectron spectroscopy （XPS）, the formation process and the protective mechanism of the surface film were also discussed. The results show that the protective film is composed of MgO, MgS and MgSO4. MgS increases the pilling and bedworth ratio of the surface film and enhances its protective capability. MgSO4 is the thermodynamically stable phase and its formation is important for the formation of protective film. When SO2/Air/N2 cover gases are used to protect the melt and SO： content is fixed, air content should be controlled within a certain range.

关 键 词：Mg 镁合金 气体保护 SO2 表面膜 

分 类 号：TG146.2[一般工业技术—材料科学与工程]