(西北工业大学 凝固技术国家重点实验室，西安 710072)
摘 要: Ca的加入大大提高了镁合金的燃点，当Ca含量大于1.7％时，Mg-Ca合金能在1 173 K的高温下暴露于大气中30 min而不燃烧。SEM和XRD分析表明: 合金表面生成了主要由氧化钙和氧化镁组成的复杂氧化膜，氧化膜内侧组织主要是Mg2Ca，该氧化膜具有保护性，但薄厚不一，极不规则。高温氧化动力学研究显示: 该合金在673 K和873 K氧化符合抛物线规律，而在773 K氧化遵循立方规律。热力学计算结果表明: 在Mg-2.5Ca合金中从室温到1 143 K温度范围内Ca都比镁优先与氧结合生成CaO，当Ca含量降低到一定程度时，镁又与氧结合生成MgO，所以形成 MgO＋CaO的复合保护膜。
关键字: Ca；镁合金； 氧化； 动力学
（ State Key Laboratory of Solidification Processing, Northwestern Polytechnical University,
Xi’an 710072, China）
Abstract: Ignition point of ignition-proof magnesium alloy was improved by the addition of calcium. When the content of Ca is larger than 1.7%, the alloy Mg-2.5Ca can avoid from ignition at 1 173 K for 30 min. XRD and SEM analyses of oxide scale reveal that the protective oxide film formed on the surface of Mg-2.5Ca alloy is composed of MgO and CaO, and beneath the film is Mg2Ca. The film has protective function, but is inhomogeneous in structure. High-temperature kinetics measurements indicate that the oxidation dynamics curves measured at 673 K and 873 K follow parabolic law and the curve investigated at 773 K follows the cubic law. Thermodynamic calculation reveals that from room temperature to 1 143 K, Ca can react with O to form CaO prior to Mg. When the content of Ca decreases to some degree, Mg can react with O to form MgO, resulting in the formation of MgO+CaO composite film.
Key words: Ca; magnesium alloys; oxidation; kinetics
