在一次性充入含0.01%HFC134a(体积分数)的氮气的密封熔炼炉中,研究了表面搅拌、熔炼温度和熔炼炉密封质量对AZ91D镁合金保护效果的影响以及气氛对熔炼坩埚内壁的腐蚀,并对表面膜形貌、厚度和成分进行了研究.研究结果表明,HFC134a适合充当镁合金在密封熔炼炉中保护气体,氮气是一种好的载气.无表面搅拌时,AZ91D镁合金的最高保护温度是865℃;有表面搅拌时,最高保护温度是800℃.允许熔炼炉内压升率超过10 kPa/min.所有保护膜呈致密胞团状结构,膜厚度在1～2μm之间,且比较均匀.而AZ91D镁合金不被保护时,表面膜呈絮状,膜厚度在2～5 μm之间变化,厚度很不均匀.随熔炼温度升高,表面膜中C含量逐渐减少到零,表面膜中氧含量逐渐升高.炉内气氛对熔炼炉内壁无可观察到的腐蚀.
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