MgF_2/N_2/空气气氛中密封熔炼AZ91D镁合金实验研究  

Experimental Study on Melting AZ91D Magnesium Alloy in a Sealed Furnace Under MgF_2/N_2/Air Protective Atmospheres

作　　者：聂书红[1] 熊守美[1] 

机构地区：[1]清华大学机械工程系先进成形制造重点实验室,北京100084

出　　处：《材料工程》2007年第12期67-72,78,共7页Journal of Materials Engineering

基　　金：清华-东洋镁铝合金成形技术研究开发中心项目(0503J08);博士后基金资助项目(2004035319)

摘　　要：在预先装入固态MgF2的密封熔炼炉中,研究了熔炼温度和炉内空气含量对AZ91D镁合金保护效果的影响,并对表面膜形貌、成分和成分分布进行了研究。结果表明:保护效果随熔炼温度和气氛中空气含量增加而逐渐变差;当气氛中空气体积分数为25%,实验温度<750℃时,AZ91D镁合金很好被保护;当熔炼温度为650℃,气氛中空气体积分数<30%时,AZ91D镁合金很好被保护。所有表面膜由MgF2和MgO组成,表面膜厚度随熔炼温度和气氛中空气含量的增加而增加,表面膜中MgF2的数量也随熔炼温度和气氛中空气含量的增加而显著增加;膜表面平整度随气氛中空气含量的增加而变差,熔炼温度增加对膜平整度影响不大。固态MgF2在熔炼温度下蒸气压较高,其蒸气与空气中氧气一起参与AZ91D镁合金表面膜的形成。The effects of holding temperature and air content in the atmosphere on the protection of AZ91D magnesium alloy were investigated in a sealed furnace enclosed solid MgF2 before the experiments. The morphology, ingredients, and ingredient distribution of the surface film were also studied. The results showed that the AZ91D specimens were not gradually protected with the increase of holding temperature and content of air in the atmosphere; AZ91D specimens were well protected under atmospheres containing 25% （volume fraction） air below 750℃ ;AZ91D specimens were also well protected under atmospheres containing 〈30% air at 650℃. All the surface films were made up of the MgF2 and MgO, the thickness of all the surface films increased with the increase of the holding temperature and the air content in the atmosphere, the MgF2 content in the surface film also increased. The surface of film became uneven with the increase of air in the atmosphere and there was no obvious influence of the holding temperature on the flatness of the surface film. Since solid MgF2 had a high vapor pressure at the melting temperature, the Mg reacted with the O2 in the atmosphere, the MgO and MgF2 formed the surface film on AZ91D.

关 键 词：镁合金 密封炉 MGF2 表面膜 

分 类 号：TB304[一般工业技术—材料科学与工程]