【摘要】 以汽车用AZ91D镁合金为研究对象,添加一定量的稀土La元素,利用扫描电镜（SEM）、能谱分析（EDS）、XRD衍射仪、静态腐蚀失重法以及NaCl溶液浸泡等方法分析基体及稀土镁合金显微组织结构、耐腐蚀性、相结构、元素分布,并对稀土La元素改善AZ91D镁合金耐腐蚀性行为机制进行分析与讨论。结果表明:在AZ91D镁合金中w（La）=1.0%时,细化了晶粒,β-Mg₁₇Al₁₂相由较大板块状转变为细片状组织,并广泛密集的分布在基体中;用w（NaCl）=3.5%的溶液浸泡12 h、24 h、36 h、48 h后的静态腐蚀失重结果表明,加入La后AZ91镁合金的腐蚀速率、腐蚀坑均远小于未加La的AZ91D镁合金的腐蚀速率和腐蚀孔洞;分析结果表明合金中晶粒的细化、元素偏析程度的减弱、β-Mg₁₇Al₁₂相数量的增多、β相的密集分布结构以及Al-La、Al-Mn-La新相的出现,提高了基体在NaCl溶液中的自腐蚀电位,从而使基体的耐蚀性有了一定程度的改善。更多还原

【Abstract】 This paper focuses on AZ91D magnesium alloy for automobile industry prepared by addition of certain lanthanum. The microstructure,corrosion resistance,phase structure and element distribution of the matrix and rare earth Mg alloy are analyzed by using scanning electron-microscopy,EDS spectrum analyzer,XRD diffractometer,static weight-loss method and immersion tests with Na Cl solutions,and the mechanism of improving corrosion behavior caused by lanthanum is also analyzed and stated. The results show that when AZ91 D magnesium alloy is added with 1. 0% lanthanum,the grains are refined,and the thick-plate shaped β-Mg₁₇Al₁₂ phases gradually change into small-flakes like structures,extensively and densely distributed in the matrix. After AZ91D magnesium alloy is immersed in Na Cl solutions（ w（ NaCl） = 3. 5%） for 12 h,24 h,36 h and 48 h,it is tested with the the static weight-loss method. The results show that the corrosion rate and the size of corrosion pits of the AZ91D magnesium alloy with La addition are far smaller than those of the AZ91D magnesium alloy without La. Analysis also shows that more refined grains,weakened segregation,more β-Mg₁₇Al₁₂ phases,dense distribution of β phase and new phases of Al-La,Al-Mn-La improve selfcorrosion potential of AZ91 D magnesium alloy in Na Cl solution,so that corrosion resistance ofAZ91 D magnesium alloy has been improved to a artm degree.更多还原