深冷处理后的MB5镁合金焊接接头微观组织及腐蚀行为

Microstructure and corrosion behavior of MB5 magnesium alloy welded joints after cryogenic treatment

本试验在对MB5镁合金进行了不同参数的CMT焊接工艺试验基础上,采用超景深显微镜、扫描电镜、X射线衍射仪和电化学工作站等分析了接头试样经深冷处理前后的微观形貌,以及其在NaCl溶液中的腐蚀行为。试验结果表明,深冷处理引起了α相和β相尺寸、分布的改变,这也引起了接头耐蚀性的改变。深冷处理过程使接头晶粒细化,β相析出增多且呈弥散网状分布于α基体相中,且这种变化随着深冷处理时间的增加和深冷处理温度的降低越来越显著,而且经深冷处理后的MB5接头试样的耐蚀性均得到了不同程度的提升,当在深冷处理温度为-180℃,保温时间为8 h时,接头试样的耐蚀性能最佳。

In this experiment,on the basis of the CMT welding process test of MB5 magnesium alloy with different parameters,the micro-morphology of the joint sample before and after cryogenic treatment was analyzed by ultra-depth microscope,scanning electron microscope, X-ray diffractometer and electrochemical workstation and its corrosion behavior in Na Cl solution. Experiments showed that cryogenic treatment causes changes in the size and distribution of αand β phases,which also changed the corrosion resistance of joints. The cryogenic process maked the grains of the joints refined,the β phase precipitation increases and was distributed in the α matrix phase in a dispersed network,and this change became more and more significant with the increase of cryogenic treatment time and the decrease of cryogenic treatment temperature,and the corrosion resistance of the MB5 joint samples after cryogenic treatment had been improved to different degrees. When the cryogenic treatment temperature was-180 ℃ and the holding time was 8 h,the corrosion resistance of the joint samples reached the best.