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采用光纤激光器焊接3 mm厚AZ31B镁合金对接接头,借助光学显微镜、扫描电子显微镜、拉伸实验机和显微硬度计对接头焊缝成形、微观组织及力学性能进行研究。结果表明,镁合金光纤激光焊接焊缝宽度窄且表面成形良好,焊接末段上表面和背部分别出现微量下塌和上凹。焊缝区为细小的等轴晶,热影响区组织相对母材发生粗化;沿焊接方向,焊缝区的晶粒尺寸逐渐增大。焊接接头热影响区硬度最低,拉伸试样的抗拉强度和延伸率可达母材的95.1%和89.3%,此时在热影响区以韧脆混合模式发生断裂。
A 3 mm thick AZ31B magnesium alloy butt joint was welded by fiber laser. The shape, microstructure and mechanical properties of the weld of the joint were studied by means of optical microscope, scanning electron microscope, tensile testing machine and microhardness tester. The results show that the laser welding of magnesium alloy fiber laser has a narrow width and a good surface finish. The upper surface and the back of the laser welding end are slightly collapsed and concave. The weld zone is a fine equiaxed grain, and the HAZ is roughened relative to the base metal. Along the welding direction, the grain size of the weld zone gradually increases. The HAZ hardness of the welded joint is the lowest, and the tensile strength and elongation of the tensile specimen reach 95.1% and 89.3% of the base material, respectively, and the fracture occurs in the ductile-brittle mode in the HAZ.