采用自制的实验装置, 研究了以SO2气体为基的混合气体对熔态AZ91D镁合金的保护行为, 运用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)及Auger电子能谱仪(AES)分析了形成的表面膜的相组成、微观组织形貌和化学成分,讨论了表面膜的生成过程和保护机理. 研究表明: 表面膜由MgO和MgS混合组成,厚度为0.5-3.0 μm, 为两层结构, 外层为MgO, 内层为MgO与MgS的复合层;表面膜呈网状结构, 边界突起区域与内部平坦区域微观特征相似, 均为层片状,且两者成分相近.
Molten magnesium alloy oxidizes rapidly during casting and handling processes, sulfur dioxide (SO2 ) mixed with carrier gases can be used to protect molten magnesium alloy by reacting with the melt to form a coherent protective film on the melt surface. In this paper, the films formed in controlled atmospheres with SO2 gas were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES), the formation process and the protective mechanism of the surface film were also discussed. The results show that the film is a network structure with similar microstructure characteristics and composition in the boundary area and the interior area. AES depth profiling and SEM observation both indicate that the film thickness is to be in a range of 0.5—3.0 μm, and the film is composed of two layers with an outer layer of MgO and a composite layer of MgO and MgS beneath the outer layer. MgS increases the pilling and bedworth ratio of the surface film and enhances its protective capability.
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