在不同焊速下进行了厚度1.4 mm 2A97铝锂合金的光纤激光焊接。通过光学显微镜观察、扫描电镜观察、拉伸试验、显微硬度试验对比了不同焊接速度下2A97激光焊接头宏观形貌、显微组织、热裂纹倾向及力学性能。结果表明:随着焊接速度的增加熔宽先减小,当速度超过一定临界值后熔宽随焊速的进一步增大而略微增大;焊缝晶粒尺寸随焊速的增大而单调减少。焊接速度过小、过大都会使接头成形质量变差。焊接速度小时,咬边严重,焊缝中易形成纵向热裂纹;焊接速度过高时,焊缝中出现横向热裂纹;本文实验条件下,在焊接速度为10m/min时获得了焊缝成形较好的接头,并对其力学性能做了测试。
The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored.The AZ31magnesium(Mg)alloy was used as the test materials.The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure.After the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth.Eventually,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably grows.During LW in subatmospheric environment,the weld penetration can be further greatly increased through power modulation.Besides,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams.Finally,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated.This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.
Jie NingSuck-Joo NaLin-Jie ZhangXiang WangJian LongWon-Ik Cho
