焊接速度对Mg-Mn系镁合金光纤激光焊接接头组织和成形的影响

采用大功率光纤激光器对Mg-Mn合金进行一系列激光焊接工艺试验，并对焊缝成形的形成规律、接头的微观组织进行研究。使用金相显微镜分析测试手段，研究光纤激光焊接接头各区域的显微组织，分析主要焊接参数(焊接速度)对焊接质量的影响。试验结果表明：当焊接功率为2 200 W、焊接速度为1 500～1 800 mm/min时，焊缝成形良好，无气孔缺陷。Mg-Mn合金激光焊接在不同的焊接参数下，焊缝的晶粒中均存在等轴晶和柱状晶，且晶粒主要组织为α-Mg固溶体和Mg8Ce金属间化合物。焊缝的组织形态受到焊接速度的影响比较明显，随着焊接速度的不断升高，焊缝的熔宽相应减小，且晶粒尺寸也随之减小。

Effects of welding speed on microstructure and weld appearance quality of fiber laser beam welded joints of Mg-Mn magnesium alloy

Mg-Mn magnesium alloy with the thickness of 4 mm was laser beam welded by using the high power fiber laser to investigate the effect of welding velocity on the weld appearance quality and microstructure. The results showed that the sound joints without porosity were obtained in the range of the welding speed from 1 500～1 800 mm/min. The columnar grains were observed near the fusion zone. And the grains were changed into fine equiaxed dendrite near the weld center. The α-Mg matrix, massive Mn phases, Mg8Ce inter-metallic compounds were observed in the joint. The greater difference of the microstructures of the joints was detected at the different welding speed. The weld width and the grain size of the joint were decreased with the increase of welding speed.