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.
YU Xian-Fei
,
XIONG Shou-Mei
. CHARACTERIZATION OF THE SURFACE FILM FORMED ON MOLTEN AZ91D MAGNESIUM ALLOY PROTECTED BY SO2 MIXTURES[J]. Acta Metall Sin, 2010
, 46(12)
: 1529
-1533
.
DOI: 10.3724/SP.J.1037.2010.00303
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