焊后塑性变形对搅拌摩擦焊AZ31镁合金耐腐蚀的影响

设计了AZ31镁合金的母材(BM)、搅拌摩擦焊接头(FSW)、焊后横向拉伸5%(FSW+T)和焊后拉伸加退火(FSW+T+A)等4组试样。通过对比4组试样在质量分数为3.5%的NaCl溶液中的耐腐蚀性能,探索焊后塑性变形对接头耐腐蚀性能的影响。结果发现,AZ31镁合金的耐腐蚀性能在搅拌摩擦焊接后显著改善,但焊后横向拉伸将显著降低接头的耐腐蚀性能,而拉伸后退火处理使接头耐腐蚀性能增强。4组试样的腐蚀速率由大到小为:BM>FSW+T>FSW≈FSW+T+A。焊后横向拉伸在AZ31镁合金焊接接头中引入拉伸孪晶及位错滑移,两者对接头的耐腐蚀性能产生不利影响,但位错滑移所起的作用更显著。

Effects of Plastic Deformation after Welding on Corrosion Resistance of Friction Stir Welded AZ31 Magnesium Alloy

Four groups of samples,including base metal(BM),FSW,FSW+T and FSW+T+A samples,were designed to investigate the effects of plastic deformation on the corrosion resistance of the joints immersed in 3.5%NaCl solution.The results reveal that the corrosion resistance of AZ31 magnesium alloy can be enhanced significantly by friction stir welding,while post-welded tension can weaken significantly the corrosion resistance of the joint,however post-annealing treatment can enhance largely the corrosion resistance.Corrosion rate of the four groups of samples is presented as follows:BM>FSW+T>FSW≈FSW+T+A.In addition,both extension twinning and dislocation slip introduced by post-welded tension have an adverse effect on the corrosion resistance of the joint,in which dislocation slip plays the key role.