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利用3种实验方法,研究了SO_2/Air/N_2气氛对纯Mg及AZ91D合金熔体的保护行为,运用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)、Auger电子能谱仪(AES)和X射线光电子能谱仪(XPS)分析了形成的表面膜的相组成、微观组织形貌和生长过程,结合热力学计算讨论了表面膜的生长与保护机理,并考查了表面膜的稳定性.研究表明:在SO_2/Air/N_2气氛中,保护性表面膜由MgO,MgS和MgSO_4混合组成,MgSO_4是热力学稳定相,它的形成至关重要.当采用SO_2/Air/N_2气氛为保护气氛且SO_2含量一定时,Air含量不能过高也不能过低.
The protective behavior of SO 2 / Air / N 2 atmosphere on pure Mg and AZ91D alloy melts was studied by three experimental methods. The effects of SO 2 / Air / N 2 atmosphere on the melt of pure Mg and AZ91D alloy were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) The phase composition, microstructure and growth process of the surface film were analyzed by energy dispersive spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The growth and protection mechanism of the surface film was discussed by thermodynamic calculation. The results show that the protective surface film is composed of MgO, MgS and MgSO_4 in the atmosphere of SO_2 / Air / N_2, and the formation of MgSO_4 is the thermodynamically stable phase.When SO_2 / Air / N_2 atmosphere to protect the atmosphere and a certain amount of SO_2, Air content can not be too high nor too low.