中文摘要：

在密封和开放条件下研究含SO2的不同气氛对AZ91D合金的保护行为,分析表面膜的形貌与成分。结果表明：在密封条件下,含SO2气体对熔体的保护需要一定量的O2;含SO2和O2的气氛通过与熔体反应,在熔体表面形成一层致密的网状结构表面膜,表面膜主要含有MgO和MgS;MgS提高了表面膜的致密度,从而提高了表面膜的保护作用。

英文摘要：

Sulphur dioxide （SO 2 ） mixed with carrier gases was used as an alternative to SF 6 to protect molten magnesium alloys. The protection behavior of AZ91D alloy in a sealed melting furnace was investigated under the atmosphere containing SO 2 with different mixed gases. The morphology and composition of the surface film were studied. The melt was well protected in an atmosphere of SO 2 and a proper amount of air, and was not protected properly in the other atmospheres. Based on the understanding of the protective effects of SO 2 in the sealed furnace, the protection mechanism of SO 2 -containing cover gases on molten AZ91D alloy was studied in an open melting furnace. The cover gas protected the melt by reacting with the melt to form a coherent protective film with a network structure on the melt surface. The film contains MgO and MgS. MgS increases the Pilling and Bedworth ratio of the surface film and enhances the protective capability of the films.