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于镁与氧的亲合力,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1023K时,当溶液中稀土的摩尔浓度大于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1,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RE2O3的复合氧化膜,且RE2O3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。
For the rare earth elements and their corresponding oxides, the electronegativity, Gibbs free energy change of oxidation reaction and the related physical parameters were analyzed. The study on the effect of rare earth elements on the oxidation resistance of magnesium alloys was done from both thermodynamic and kinetic points. The results show that heavier rare earth elements have larger 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 larger than 0.14 at 1 023 K, the displacement reactions between rare earth elements and MgO could take place. The observations present that the density coefficient of the rare earth oxides is larger than 1 with good protection, except Yb and Eu oxide films. The oxide films can be divided into two layers, i.e. the outer layer is MgO and the interior layer consists of MgO and rare earth oxides, and the latter improve the MgO film loosening and further fill up the voids there, which can efficiently restrain the oxidation of ma.qnesium alloys.
出处
《铸造》
CAS
CSCD
北大核心
2010年第6期553-557,共5页
Foundry
基金
国家科技发展计划资助项目(2006BA104B04-1
2006BAE04B07-3)
吉林省长春市科技发展计划资助项目(2007KZ05)
关键词
镁合金
稀土
氧化膜
热力学
动力学
magnesium alloys
rare earth
oxidization film
thermodynamics
kinetics
