中文摘要：

在一次性充入含一定比例SO2的氮气的密封炉内,研究了SO2浓度、熔炼温度和加入CO2气体对AZ91D镁合金熔体的保护效果,并对表面膜形貌和成分进行了研究。结果表明：AZ91D合金表面都有菜花状氧化物生成,提高SO2气体浓度,AZ91D合金被保护面积增加;升高温度,镁合金保护效果下降明显,700℃时便完全得不到保护。成分分析表明：菜花状氧化物主要为MgO,生成的表面膜除含有Mg,O,Al元素外,还含有少量的S元素;当加入一定量CO2时,镁合金保护效果得到提高,膜中生成了无定形C。

英文摘要：

The effects of the SO2 concentration,the melting temperature and the addition of CO2 on the protection of molten AZ91D alloy were investigated in a sealed furnace filled once with an atmosphere containing SO2.The morphology and composition of the surface film were also studied.Results show that cauliflower-like oxides are formed on almost all the surface of AZ91D alloy,the protective area increases with the increase of SO2 concentration.Increasing the melting temperature reduces the protective effect on AZ91D alloy,and the alloy is completely not protected when the temperature reaches 700℃.Results also indicate that the cauliflower-like oxides are only composed of MgO,and the protected surface film contains Mg,O,Al and S elements.When CO2 is added into the atmosphere,the protective effect on AZ91D alloy is improved and C element is formed in the surface film.