使用SO2/Air/N2气氛作为纯Mg及 AZ91D合金的熔炼保护*
王先飞, 男, 1986年生, 博士生
收稿日期: 2013-07-08
修回日期: 2013-07-08
网络出版日期: 2013-09-04
基金资助
*国家自然科学基金项目51275269, 国家科技支撑计划重点项目2011BAE22B02和科技部国际科技合作计划项目 2010DFA72760资助
USE OF SO2/AIR/N2 COVER GASES FOR THE PROTECTION ON MOLTEN MAGNESIUM AND AZ91D ALLOY
Received date: 2013-07-08
Revised date: 2013-07-08
Online published: 2013-09-04
Supported by
Supported by National Natural Science Foundation of China (No.51275269), National Key Technologies R&D Program (No.2011BAE22B02) and International S&T Cooperation Program of China (No.2010DFA72760)
利用3种实验方法, 研究了SO2/Air/N2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SO2/Air/N2气氛中, 保护性表面膜由MgO, MgS和MgSO4混合组成, MgSO4是热力学稳定相, 它的形成至关重要. 当采用SO2/Air/N2气氛为保护气氛且SO2含量一定时, Air含量不能过高也不能过低.
王先飞 , 熊守美 . 使用SO2/Air/N2气氛作为纯Mg及 AZ91D合金的熔炼保护*[J]. 金属学报, 2014 , 50(1) : 32 -40 . DOI: 10.3724/SP.J.1037.2013.00386
Molten magnesium and AZ91D alloy oxidize rapidly during casting process, sulfur dioxide (SO2) mixed with carrier gases can be used to protect the melt by reacting with the melt to form a coherent protective film on the melt surface. In this work, the films formed in SO2/Air/N2 cover gases were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), the formation process and the protective mechanism of the surface film were also discussed. The results show that the protective film is composed of MgO, MgS and MgSO4. MgS increases the pilling and bedworth ratio of the surface film and enhances its protective capability. MgSO4 is the thermodynamically stable phase and its formation is important for the formation of protective film. When SO2/Air/N2 cover gases are used to protect the melt and SO2 content is fixed, air content should be controlled within a certain range.
Key words： magnesium; magnesium alloy; gas protection; SO2; surface film
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