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研究了真空度对液态AZ91D镁合金的氧化燃烧及蒸发行为的影响,并对AZ91D镁合金在不同真空条件下的试样进行能谱分析及保护膜表面形貌观察。结果表明,真空度为50kPa是AZ91D镁合金真空差压铸造的临界值。当真空度<50kPa时,液态AZ91D镁合金表面均会出现不同程度的氧化燃烧现象,且真空度越低,镁液蒸发越严重;真空度≥50kPa时,试样中镁未减少,且镁液保护膜的表面形貌逐渐趋于连续、致密,较好地抑制了镁液氧化燃烧现象。当真空度<50kPa时,在保护膜的表面形貌中存在明显的“孔洞”、“裂纹”。通过镁元素质量分数与真空度之间的关系建立了数学模型,该模型对AZ91D镁合金真空差压铸造具有参考意义。适合于AZ91D镁合金真空差压铸造的最佳真空度为50kPa。
The effect of vacuum degree on the oxidation combustion and evaporation behavior of liquid AZ91D magnesium alloy was studied. The energy spectrum of AZ91D magnesium alloy under different vacuum conditions and the observation of surface morphology of the protective film were observed. The results show that the vacuum degree of 50kPa is the critical value of AZ91D magnesium alloy vacuum differential pressure casting. When the vacuum degree is less than 50kPa, the surface of AZ91D magnesium alloy will be oxidized and burned to some extent, and the lower the vacuum, the more serious the magnesium solution evaporates. When the vacuum degree is more than 50kPa, the magnesium in the sample does not decrease, The surface morphology of the protective film tends to be continuous, dense, and better inhibited the oxidation of magnesium liquid combustion phenomenon. When the degree of vacuum <50kPa, there are obvious “holes”, “cracks” in the surface morphology of the protective film. The mathematical model was established by the relationship between the mass fraction of magnesium and the degree of vacuum. This model has reference value for the vacuum differential pressure casting of AZ91D magnesium alloy. Suitable for AZ91D magnesium alloy vacuum pressure casting the best vacuum 50kPa.