AM50镁合金表面激光熔凝层的组织与耐蚀性能

Microstructure and Corrosion Resistant Property of Laser Surface Melting Layer of AM50 Magnesium Alloy

采用CO2连续激光对AM50镁合金表面进行熔凝处理。利用扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)等手段对熔凝层的组织与成分进行了分析,通过在质量分数为3.5%的NaCl溶液中的电化学极化曲线测试和浸泡实验对激光熔凝层的耐蚀性能进行了检测。激光熔凝处理使镁合金的组织得到高度细化,组织与成分分布更加均匀,β相减少,Al及杂质元素的固溶度增加。极化曲线测试结果表明,激光熔凝表面的腐蚀电位较未处理试样提高了37mV,阳极腐蚀电流密度约降低了一个数量级;浸泡实验结果显示,激光熔凝表面腐蚀坑的出现时间和扩展速率明显慢于未处理试样,激光熔凝处理使镁合金的耐蚀性能有了明显提高。

Surface of AM50 magnesium alloy was melted using continuous wave CO2 laser. The microstructure and composition of the melted layer were analysed by scanning electron microscope （SEM）, energy dispersion spectrum （EDS） and X-ray diffraction （XRD）. The corrosion behaviour of the laser-treated and untreated samples were studied in 3.5% （mass fraction） NaCI solution by measuring electrochemical polarization curves and immerging. The microstrueture of the melted layer was refined highly, the composition and structure were more uniform, the β-phase was decreased, AI and impurity elements in solid solution were increased. The experimental results show that the corrosion potential of the laser melted sample is about 37 mV higher than that of the as-received sample, while the anodic current density is about one order of magnitude lower and the pitting corrosion develop more slowly. The corrosion resistance of the laser surface melting of AM50 is significantly improved.