郝維新，王 梅，周堯和
(西北工業(yè)大學(xué) 凝固技術(shù)國家重點(diǎn)實(shí)驗(yàn)室，西安 710072)
摘 要: Ca的加入大大提高了鎂合金的燃點(diǎn)，當(dāng)Ca含量大于1.7％時(shí)，Mg-Ca合金能在1 173 K的高溫下暴露于大氣中30 min而不燃燒。SEM和XRD分析表明: 合金表面生成了主要由氧化鈣和氧化鎂組成的復(fù)雜氧化膜，氧化膜內(nèi)側(cè)組織主要是Mg2Ca，該氧化膜具有保護(hù)性，但薄厚不一，極不規(guī)則。高溫氧化動力學(xué)研究顯示: 該合金在673 K和873 K氧化符合拋物線規(guī)律，而在773 K氧化遵循立方規(guī)律。熱力學(xué)計(jì)算結(jié)果表明: 在Mg-2.5Ca合金中從室溫到1 143 K溫度范圍內(nèi)Ca都比鎂優(yōu)先與氧結(jié)合生成CaO，當(dāng)Ca含量降低到一定程度時(shí)，鎂又與氧結(jié)合生成MgO，所以形成 MgO＋CaO的復(fù)合保護(hù)膜。
關(guān)鍵字: Ca；鎂合金； 氧化； 動力學(xué)
XIE Hui,HAO Wei-xing, WANG Mei, ZHOU Yao-he
（ 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
