SO_2/CO_2气体对纯镁及AZ91D合金的保护行为

Protection behavior of SO_2/CO_2 gas for pure magnesium and AZ91D alloy

为探究气体保护纯镁及镁合金免于氧化及燃烧的机制,研究了体积分数为3%SO2和97%CO2混合气体在非封闭熔化炉中对熔融纯镁及AZ91D合金的保护行为。借助具有能谱测定(EDS)的扫描电镜(SEM)、X射线衍射仪(XRD)分别分析了熔融纯镁及AZ91D合金表面膜的显微组织、化学成分及相组成。结果表明:在680℃AZ91D合金表面膜密集连续,其厚度约为2μm,而纯镁表面膜厚度约为1μm,混合气体对AZ91D合金的保护效果优于纯镁。两种熔体表面膜由MgO、MgS及少量单质C相组成。除AZ91D表面膜含有少量Al外,两种表面膜均含有S、C、O及Mg元素。

Aimed at exploring the mechanism by which gas protects pure magnesium and AZ91D alloy from oxidation and combustion, this paper introduces an investigation into the protection behavior of gas mixture with volume fraction of 3% SO2 and 97% CO2, as is the case with pure magnesium and AZ91D alloy in an open melting furnace. The analysis of mierostructures, chemical compositions, and phase compositions of surface film found on molten pure magnesium and AZ91 D alloy by scanning electron microscopy （SEM） with energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）, shows that AZ91D behaving at 680 ℃ alloy has dense and coherent surface films with an average thickness of 2 μm, while pure magnesium has surface films with an average thickness of 1 μm. The gas mixture exerts a better protective effect on AZ91D alloy than on pure magnesium. Both pure magnesium and AZ91D alloy exhibit the surface films consisting of MgO, MgS and a small amount of C phases, together with ele- ments S, C, O and Mg, excluding a few elements A1 in AZ91D alloy.