AZ31B镁合金功率调制环形光斑光纤激光焊接试验研究

doi:10.3901/JME.2025.02.151

摘要/Abstract

摘要： 镁合金激光焊接的关键的缺陷是焊缝成形差、晶粒粗化及接头性能差。提出环形光斑光纤激光束与功率正弦调制协同作用的镁合金激光深熔焊新工艺，并深入分析了功率调制参数对AZ31B镁合金对接接头表面成形、显微组织和力学性能的影响。结果表明，与恒功率环形光斑激光焊相比，中心光束功率调制环形光斑激光焊缝上表面塌陷显著改善，且成形均匀。中心光束功率调制环形光斑激光焊时，熔池表面熔融金属波动速度较低，焊接小孔和上表面熔池流动更为稳定，有助于产生均匀的鱼鳞纹焊缝。中心光束功率调制可以改变焊缝显微组织结构，合适的调制频率下焊缝中心细小等轴晶区宽，热影响产生的粗晶区窄；过大的调制频率时，焊缝中心等轴晶区消失，形成大量粗晶区，但晶粒内部形成大量变形晶粒。当中心光束功率调制振幅和频率分别为500 W和200 Hz时，接头抗拉强度高达233.41 MPa，伸长率为9.52%，分别约为母材的82.3%和76%，断口以韧性断裂为主，局部存在解理特征。

关键词: 激光焊接, AZ31B镁合金, 环形光斑, 功率调制, 组织性能

Abstract: Three common issues in magnesium alloy laser welding are poorly formed weld-seams, coarsen grains and deteriorated quality of joints. A novel process to weld magnesium alloys by laser deep melting is proposed, and it synergizes the effect of the circular spot of fiber laser and the sinusoidal modulation of power. The impact of power modulation parameters on surface formation, microstructure, and the mechanical properties of butt joints has been investigated thoroughly, and AZ31B is used as the welding materials in investigation. By comparing the welds from a circular spot laser with constant power, the investigation finds that the proposed process has improved surface collapse in weld seam significantly, the welds are formed uniformly when a circular spot laser with a central beam power modulation is applied. Moreover, a low fluctuation of the speed of molten metal on welded surface has produced more stable keyholes and fish-scale patterns on the welds uniformly. It is found that central beam power modulation also improves the microstructure of welds. By setting a modulation frequency appropriately, the zone with fine equiaxed crystals has been widened in the center of welds, and the zone with coarse crystals in the heat-affected zone has been reduced. However, when the modulation frequency is too high, the zone with equiaxed crystals is eliminated in the center of weld, and it forms numerous coarse crystals and some grains with internal deformation. When the amplitude and frequency of power modulation are as 500 W and 200 Hz, respectively, the tensile strength of joint reaches 233.41 MPa, and the corresponding elongation rate is 9.52%; these welding properties are approximately 82.3% and 76% of the base material, respectively. The failure modes are primary ductile fractures globally and secondary intergranular fractures in locally.

Key words: laser welding, AZ31B magnesium alloy, ring-mode laser beam, power modulation, microstructure and performance

中图分类号:

TG456

张明军, 李晨希, 邹江林, 程波, 张健, 仝永刚, 胡永乐, 陈根余. AZ31B镁合金功率调制环形光斑光纤激光焊接试验研究[J]. 机械工程学报, 2025, 61(2): 151-161.

ZHANG Mingjun, LI Chenxi, ZOU Jianglin, CHENG Bo, ZHANG Jian, TONG Yonggang, HU Yongle, CHEN Genyu. Experimental Research on Laser Welding of AZ31B Magnesium Alloy Using Power-modulated Ring-mode Fiber Laser[J]. Journal of Mechanical Engineering, 2025, 61(2): 151-161.

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