真空熔炼AZ91镁合金过程中Mg元素的蒸发行为

The Evaporation of Mg during Vacuum Smelting of AZ91 Magnesium Alloy

在真空Ar气氛中熔炼AZ91镁合金，测定了不同精炼温度下Mg元素的蒸发速率。结果表明，随着精炼温度的升高，Mg元素的蒸发量增大。通过计算可知，Mg的蒸气压是Al的10^9倍，是Zn的46倍，因此主要是Mg的蒸发而导致合金其他元素含量升高。XRD分析表明，蒸发物是Mg元素。结合Mg元素的蒸发机制，在该试验条件下推导出Mg元素蒸发率的计算公式以及Mg元素的表观传质系数、蒸发率与精炼温度的关系，计算得出Mg元素蒸发率为0．86×10^-3-1．35×10^3g／cm^2·s，Mg元素的表观传质系数在2×10^-5-24×10^-5cm／s范围内。

AZ91 magnesium alloy was smelted in Ar atmosphere and the evaporation rates of Mg at different refining temperature were detected, It is shown that the evaporation rate of Mg increased with the increase of the refining temperature. According to calculating of the saturated pressure of main elements in AZ91, it is found that the saturated pressure of Mg was 109 times of that of Al, 46 times that of Zn, therefore, the evaporation of Mg is the main reason for the increasing of other elements. XRD was used to test the metallic dust at the furnace wall, it was justified that Mg was evaporant （metallic dust）. Based on the mechanism of Mg evaporation, the formula of the evaporation rate of Mg and the relationships among mass transfer coefficient, evaporation rate and refining temperature were deduced. It is calculated that the evaporation rate of Mg is about 0.86×10^-3-1.35 ×10^-3 g/cm2＂s and the mass transfer coefficient is about 2×10^-5-24×10^-5 cm/s.