FeS_2对AZ91D镁合金熔炼保护机理研究

Protective Mechanization of FeS_2 on AZ91D Magnesium Alloy Melt

在空气气氛的镁合金密封熔炼炉中加入固态硫铁矿(FeS2),研究了FeS2对AZ91D镁合金熔炼的保护效果,并采用SEM、EDS和XRD等检测分析技术对保护膜形貌、成分和相组成进行了研究。研究结果表明,在空气气氛中,硫铁矿对镁合金熔炼有良好的保护效果。在730℃中保温30 min时保护膜由MgS、MgO和MgF2混合物组成,保护膜致密;保护膜的厚度随保温时间的延长而增加,其厚度在1.0-2.0μm之间。FeS2在空气中分解和氧化生成S和SO2,产物与空气中的O2以及镁液反应生成MgS和MgO,使镁熔体表面氧化膜变致密,从而起到熔炼保护作用。通过热力学分析可知,受热时硫铁矿消耗密封熔炼炉内的氧,并且在表面膜中MgS形成趋势大,形成的MgS的稳定性比MgO好。

The protective effect of FeS2 on AZ91D magnesium alloy melted in a sealed furnace has been researched,and SEM,EDS and XRD were also used to analyze the characteristics of the surface film formed in controlled condition.Results show that the air containing sulphur produced by FeS2 can protect AZ91D magnesium alloy well.When melted at 730 ℃ for 30 min,the principal phases in the surface films formed in the air containing sulphur are MgF2,MgS and MgF2.The films are dense,and as the holding time increased it became thicker,being 1.0~2.0 μm.In the air,FeS2 decompose,react and form S and SO2 which then react with O2 in the air and Mg,forming MgS and MgO.All these made the surface film being more denser and being protective on the magnesium alloy melt.Thermodynamic analysis shows that FeS2 can decrease O2 content,and MgS can formed easer and be more stable than MgO.