Ce与Ca复合添加对Mg-9Al-Zn合金组织及耐蚀性的影响

Effects of Ce and Ca Addition on Microstructure and Corrosion Resistance of Mg-9Al-Zn Alloy

采用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射(XRD)、极化曲线测试、扫描开尔文探针力显微镜(SKPFM)等方法,研究了0.6%(质量分数,下同)Ce与0.3%Ca、0.8%Ca复合添加对Mg-9Al-Zn合金微观组织与耐蚀性的影响。结果表明:Mg-9Al-Zn合金中加入0.6%Ce后,合金组织由连续网状变为断续、弥散分布,Ce与Al结合生成Al2Ce相,降低了阴极相β-Mg(17)Al(12)的体积分数,腐蚀速率明显降低,合金的耐蚀性显著提高;在Mg-9Al-Zn-0.6Ce合金的基础上加入0.3%Ca,Ca固溶于β-Mg(17)Al(12)相中,降低了β-Mg(17)Al(12)相与α-Mg相之间的电位差,其腐蚀速率相比于Mg-9Al-Zn合金的降低了54.14%,腐蚀电流密度显著降低,耐蚀性得到进一步提高,但当Ca的添加量为0.8%时,生成了Al4Ca相,阴极相数量明显增多,耐蚀性相比于加入0.3%Ca时的有所降低。

The effects of the combined addition of minor Ce and Ca on the microstructure and corrosion resistance of Mg-9Al-Zn alloy were studied by OM,SEM,XRD,scanning Kelvin probe force microscopy(SKPFM)and polarization curve test.The results showed that after adding 0.6%Ce to Mg-9Al-Zn alloy,the morphology of precipitate phases changed from continuous network to discontinuous and dispersive one.Ce reacted with Al to form Al2Ce phase,which caused the reduction in content of cathodic phaseβ-Mg17Al12,and the corrosion resistance of the alloy was improved obviously.After further adding 0.3%Ca to Mg-9Al-Zn-0.6Ce,Ca was dissolved in theβ-Mg17Al12 phase,reducing the potential difference between theβ-Mg17Al12phase andα-Mg phase.The corrosion rate of Mg-9Al-Zn-0.6Ce-0.3Ca alloy was reduced by 54.14%compared with Mg-9Al-Zn alloy,and the corrosion current density was also significantly reduced,hence the corrosion resistance was further improved.However,when the Ca addition raised to 0.8%,Al4Ca phase was formed,and the amount of the cathodic phases significantly increased,leading to the reduction of corrosion resistance compared with the Mg-9Al-Zn-0.6Ce-0.3Ca alloy.