Experimental Research on Laser Welding of AZ31B Magnesium Alloy Using Power-modulated Ring-mode Fiber Laser

doi:10.3901/JME.2025.02.151

Abstract

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

CLC Number:

TG456

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.

References

[1] 李建伟，何智，龙建周，等. 搅拌摩擦处理对镁合金电弧增材修复层缺陷调控[J]. 机械工程学报，2022，58(4)：55-61. LI Jianwei，HE Zhi，LONG Jianzhou，et al. Control of defects in Mg alloy arc additive repair layer by friction stir treatment[J]. Journal of Mechanical Engineering，2022，58(4)：55-61.
[2] 冯吉才. 异种材料连接研究进展综述[J]. 航空学报，2022，43(2)：6-42，457. FENG Jicai. Research progress on dissimilar materials joining[J]. Acta Aeronautica et Astronautica Sinica，2022，43(2)：6-42，457.
[3] 李永兵，马运五，楼铭，等. 轻量化薄壁结构点连接技术研究进展[J]. 机械工程学报，2020，56(6)：125-146. LI Yongbing，MA Yunwu，LOU Ming，et al. Advances in spot joining technologies of lightweight thin-walled structures[J]. Journal of Mechanical Engineering，2020，56(6)：125-146.
[4] 宋刚，赵爽，李涛涛，等. 镁合金与钢异质材料焊接的研究进展[J]. 机械工程学报，2020，56(8)：1-12. SONG Gang，ZHAO Shuang，LI Taotao，et al. Research progress on welding of magnesium alloy and steel dissimilar materials[J]. Journal of Mechanical Engineering，2020，56(8)：1-12.
[5] 陈怡，郭龙涛，祁同福，等. 镁合金铸件氦-氩保护TIG焊修复工艺[J]. 焊接学报，2021，42(9)：35-41，99. CHEN Yi，GUO Longtao，QI Tongfu，et al. Repair process of magnesium alloy casting by He-Ar mixed gas TIG welding[J]. Transactions of the China Welding Institution，2021，42(9)：35-41，99.
[6] 李会明，周惦武，王新宇，等. 胶层-镍箔辅助激光焊钢/镁接头组织与性能[J]. 焊接学报，2022，43(8)：61-67，117. LI Huiming，ZHOU Dianwu，WANG Xinyu，et al. Microstructure and properties of steel/magnesium joint for adhesive layer-Ni foil assisted laser welding[J]. Transactions of the China Welding Institution，2022，43(8)：61-67，117.
[7] 邹江林，王利达，祝宝琦，等. 光纤激光-TIG电弧复合焊接等离子体形态的可视化观察[J]. 中国激光，2019(12)：1202007. ZOU Jianglin，WANG Lida，ZHU Baoqi，et al. Visual observation of plasma morphology during fiber laser-TIG arc-hybrid welding[J]. Chinese Journal of Lasers，2019(12)：1202007.
[8] 聂浩，徐洋，柯黎明，等. 转速对厚板铝/镁异种材料搅拌摩擦焊摩擦产热及界面组织的影响[J]. 材料导报，2023(8)：1-11. NIE Hao，XU Yang，KE Liming，et al. Effect of rotational speed on frictional heat production and interface structure of thick plate Al/Mg dissimilar materials by friction stir welding[J]. Materials Reports，2023(8)：1-11.
[9] YANG Hongwei，CUI Zeqin，WANG Wenxian，et al. Fatigue behavior of AZ31B magnesium alloy electron beam welded joint based on infrared thermography[J]. Transactions of Nonferrous Metals Society of China，2016，26(10)：2595-2602.
[10] 吴晓明，陈丽园，景锋，等. AZ61A镁合金等离子焊接头组织与性能[J]. 电焊机，2017，47(10)：50-52，57. WU Xiaoming，CHEN Liyuan，JING Feng，et al. Microstructure and properties of plasma welded joints of AZ61A magnesium alloy[J]. Electric Welding Machine，2017，47(10)：50-52，57.
[11] 胡浩，刘飞，侯庆磊，等. 基于Ti中间层的AZ31B镁合金/6061铝合金电阻点焊研究[J]. 稀有金属材料与工程，2022，51(6)：2209-2214. HU Hao，LIU Fei，HOU Qinglei，et al. Research on resistance spot welding of AZ31B magnesium alloy/6061 aluminum alloy based on Ti interlayer[J]. Rare Metal Materials and Engineering，2022，51(6)：2209-2214.
[12] 康粟，李冬晓，李晓光，等. 铝合金搅拌摩擦焊力的周期性波动特征与机制[J]. 机械工程学报，2022，58(12)：55-63. KANG Su，LI Dongxiao，LI Xiaoguang，et al. Characteristic and mechanism of eriodic oscillation of force in friction stir welding of aluminum alloy[J]. Journal of Mechanical Engineering，2022，58(12)：55-63.
[13] 戎易，李海涛，熊震宇，等. 镁合金/钢异种材料激光熔钎焊接头组织及成形调控[J]. 材料工程，2022，50(5)：166-171. RONG Yi，LI Haitao，XIONG Zhenyu，et al. Microstructure and forming control of laser welding- brazing joint of magnesium alloy and steel dissimilar materials[J]. Journal of Materials Engineering，2022，50(5)：166-171.
[14] 陈怡，邹文兵，郭龙涛，等. 铸造镁合金的焊接修复技术研究现状及发展方向[J]. 材料导报，2020，34(15)：15126-15131. CHEN Yi，ZOU Wenbing，GUO Longtao，et al. A review and development tendency of welding repair technology for cast magnesium alloy[J]. Materials Reports，2020，34(15)：15126-15131.
[15] TAN C，LIU Y，LIU F，et al. Effect of laser power on laser joining of carbon fiber reinforced plastic to AZ31B Mg alloy[J]. Optics & Laser Technology，2022，145：107449.
[16] HAO K，GAO Y，XU L，et al. Plasticity improvement coupled by carbon nanotubes and beam oscillation in laser-arc hybrid welding of magnesium alloy[J]. Materials Science and Engineering：A，2022，857：144093.
[17] GAO M，WANG H，HAO K，et al. Evolutions in microstructure and mechanical properties of laser lap welded AZ31 magnesium alloy via beam oscillation[J]. Journal of Manufacturing Processes，2019，45：92-99.
[18] POURANVAR M. Critical review on fusion welding of magnesium alloys：Metallurgical challenges and opportunities[J]. Science and Technology of Welding and Joining，2021，26(8)：559-580.
[19] 张迪，赵琳，刘奥博，等. 激光能量对激光焊接接头熔化形状、气孔和微观组织的影响及其调控方法[J]. 中国激光，2021，48(15)：1502005. ZHANG Di，ZAHO Lin，LIU Aobo，et al. Understanding and controlling the influence of laser energy on penetration，porosity，and microstructure during laser welding[J]. Chinese Journal of Lasers，2021，48(15)：1502005.
[20] WANG Z，OLIVEIRA J P，ZENG Z，et al. Laser beam oscillating welding of 5A06 aluminum alloys：Microstructure，porosity and mechanical properties[J]. Optics & Laser Technology，2019，111：58-65.
[21] MAINA M R，OKAMOTO Y，OKADA A，et al. High surface quality welding of aluminum using adjustable ring-mode fiber laser[J]. Journal of Materials Processing Technology，2018，258：180-188.
[22] WANG L，GAO X D，KONG F R. Keyhole dynamic status and spatter behavior during welding of stainless steel with adjustable-ring mode laser beam[J]. Journal of Manufacturing Processes，2022，74：201-219.
[23] 朱志勇，陈辉，马彦龙，等. 脉冲激光对B950CF高强钢复合焊接头组织及疲劳性能的影响[J]. 中国激光，2021，48(14)：63-73. ZHU Zhiyong，CHEN Hui，MA Yanlong，et al. Effects of pulsed laser on the microstructure and fatigue properties of B950CF high-strength steel hybrid welding joint[J]. Chinese Journal of Lasers，2021，48(14)：63-73.
[24] HEIDER A，WEBER R. Power modulation to stabilize laser welding of copper[J]. Journal of Laser Application，2015，27：022003.
[25] DUOCASTELLA M，ARNOLD C B. Bessel and annular beams for materials processing[J]. Laser & Photonics Reviews，2012，6(5)：607-621.
[26] KRONTHALER M R，BRAUNREUTHER S，ZAEH M F. Bifocal hybrid laser welding-more than a superposition of two processes[J]. Physics Procedia，2011，12：208-214.
[27] JARWITZ M，LIN D J，WEBER R，et al. Investigation of the influence of superimposed intensity distributions on spatter behavior in laser welding of steel using online X-ray diagnostics[C]//International Congress on Applications of Lasers & Electro-Optics，October 14-18，2018，Laser Institute of America，Orlando，FL，2018：703.
[28] LI Q，LUO M，MU Z，et al. Improving laser welding via decreasing central beam density with a hollow beam[J]. Journal of Manufacturing Processes，2022，73：939-947.
[29] 张明军，吴乐峰，毛聪，等. AZ31B镁合金可调环形光纤激光焊接试验研究[J]. 中国激光，2022，49(22)：2202002. ZHANG Mingjun，WU Lefeng，MAO Cong，et al. Experimental research on laser welding of AZ31B magnesium alloy using adjustable ring-mode fiber laser[J]. Chinese Journal of Lasers，2022，49(22)：2202002.
[30] NING J，NA S J，ZHANG L J，et al. Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment[J]. Journal of Magnesium and Alloys，2022，10(10)：2788-2800.
[31] ZHANG M，WU J，MAO C，et al. Impact of power modulation on weld appearance and mechanical properties during laser welding of AZ31B magnesium alloy[J]. Optics & Laser Technology，2022，156：108490.
[32] ZHU B，ZHANG G，ZOU J，et al. Melt flow regularity and hump formation process during laser deep penetration welding[J]. Optics & Laser Technology，2021，139：106950.
[33] STRITT P，WEBER R，GRAF T，et al. Laser power modulation at the threshold from heat-conduction to deep-penetration welding[C]//International Congress on Applications of Lasers & Electro-Optics，September 15-17，2010，Laser Institute of America，Anaheim，California，2010，103：217-224.
[34] 赵乐，曹政，邹江林，等. 高功率光纤激光深熔焊接小孔的形貌特征[J]. 中国激光，2020，47(11)：79-84. ZHAO Le，CAO Zheng，ZOU Jianglin，et al. Keyhole morphological characteristics in high-power deep penetration fiber laser welding[J]. Chinese Journal of Lasers，2020，47(11)：79-84.