稀土镁合金抗氧化的机理.pdfVIP

学兔兔 Jun．2010 铸 造 VoI．59 NO．6 FOUNDRY ·553· 稀土镁合金抗氧化的机理 苏桂花，曹占义 (吉林大学材料科学与工程学院汽车材料教育部重点实验室，吉林长春 130025) 摘要：分析了稀土元素及其氧化物的电负性、氧化反应Gibbs自由能变及相关物性参数，系统指出稀土元素对镁合金 抗氧化性能的影响，并分别从热力学和动力学的角度对相应的作用机理进行了分析。研究表明稀土与氧的亲合力大干 镁与氧的亲合力，且重稀土比轻稀土的亲合力更强，但Yb的性质与La、ce等轻稀土的相近。温度为1 023K时，当溶液 中稀土的摩尔浓度大干0．14时，所有稀土都有可能与MgO发生置换反应。氧化物物性分析显示除Yb和Eu外的稀土氧化 膜的致密度系数都大于l，有较好地保护作用。加入适量稀土的镁合金熔液表面的氧化膜分两层，外层为MgO，内层为 MgO和RE20，的复合氧化膜，且RE20 填补了MgO氧化膜中的疏松和孔洞，可以有效抑制镁合金的进一步氧化。 关键词：镁合金；稀土；氧化膜；热力学；动力学 中图分类号：TG146．2+2 文献标识码：A 文章编号：100l一4977(2010)06—0553—05 Oxidation Resistance Mechanism of Rare Earth Magnesium Alloy SU Gui—hua，CAO Zhan-yi (Key Laboratory of Automobile Materials of Ministry Education，Departmenrt of Materials Science and Engineering，Jilin University，Changchun 1 30025，Jilin，China) Abstract：For the rare earth elements and their cOrrespOndjna oxides，the electronegativity，Gibbs free energY change of oxidation reaction and the related physicaI parameters were analyzed．The study on the effect of rare earth elements on the oxidation resistarice of magnesium alloys was done from both thermodynamic and kinetic points．The results show that heavier rare earth elements have Iarger affinity to oxygen than lighter ones：however，any rare earth element presents good affinity to oxygen when compared with magnesium。But the affinity to oxygen of Yb iS similar to that of La．Ce etc．It iS also found when the molar COncentratiOn of earth elements iS Iarger than 0．1 4 at 1 023 K． the displacement reactions between rare earth elements and MgO could take place．The observations presen