钙在铸造镁合金中的作用

The Role of Calcium in Cast Magnesium and Magnesium Alloys

钙加入到镁合金中可以提高其在空气中的着火点,含钙2%～5%的镁合金的着火点接近750℃,在通常的熔炼温度范围内不发生燃烧;少量的钙加入到镁合金中可细化镁合金的铸造组织,并提高其力学性能;此外,适量的钙在镁合金中形成热稳定性很高的第二相,显著提高镁合金的高温强度及蠕变性能,成为重要的汽车用低成本高温抗蠕变镁合金。

The addition Ca to Mg alloys significantly raised the ignition point of the molten alloys in air, the ignition point of the molten Mg alloys containing 2%～5% Ca is about 750℃, the ignition and burning of molten Mg alloys are suppressed by Ca bearing stable oxide film. A small mount of Ca addition to Mg alloys results in structural refinement and mechanical properties increase. Moreover, the Mg alloys containing Ca offer a thermally stable second phase, Al2C/Mg2Ca, suppressing the formation of the low melting point eutectic phase Mg17 Al12 at the grain boundaries, and markedly improving elevated temperature strength and creep property, which become a promising low-cost Mg alloy for automobile industry.