Beam oscillating parameters on pore inhibition,recrystallization and grain boundary characteristics of laser-arc hybrid welded AZ31 magnesium alloy

Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of beam oscillation parameters on pore inhibition,microstructure,grain boundary characteristics and tensile properties were investigated.The results showed that the pore formation can be inhibited with oscillating frequency higher than 75 Hz and radius smaller than 0.5 mm.The columnar grains neighboring the fusion line can be broken by the beam oscillation behavior,while the grain growth was promoted with the increase of frequency or radius.It should be noted that the coincidence site lattice(CSL)boundaries were mainlyΣ13b andΣ29 boundaries,which were contributed by{10■2}tensile twins and{11■2}compression twins,respectively.The total fraction of CSL boundaries reached maximum at radius of 0.25 mm and frequency of 75 Hz,which was also confirmed as the optimized parameters.In this case,the elongation rate increased up to 13.2%,12.8%higher than that of the weld without beam oscillation.Finally,the pore formation and inhibition mechanisms were illustrated according to the state of melt flow and keyhole formation,the abnormal growth was discussed basing on secondary recrystallization,and the relationship among the pore formation,grain size,boundary characteristics and weld toughness were finally established.

Microstructure homogeneity and mechanical properties of laser-arc hybrid welded AZ31B magnesium alloy

Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores.The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center.It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone,with the difference mainly affected by laser power rather than welding current and welding speed.The welding parameters were optimized as laser power of 3.5 kW,welding current of 100 A and welding speed of 1.5 m/min.In this case,the weld was free of undercut and pores,and the tensile strength and elongation rate reached 252 MPa and 11.2%,respectively.Finally,the microstructure homogeneity was illustrated according to the heat distribution,and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.

Research on laser-arc hybrid welding technology for long-distance pipeline construction

In recent years, the research on pipeline laser-arc hybrid welding technology has been the important and difficult in the field of welding all over the world. China Petroleum Pipeline Research Institute Co. Ltd. has firstly developed pipeline laser-arc hybrid welding system in China, and executed the welding tests based on X70/X80 steel. Preliminary experiment results showed that hybrid welding could meet the requirements of related standards such as API1104,ASME,etc., the mechanical properties of girth seam are qualified in the case that there were no internal defects. With the development of high-power fiber laser and the continuous improvement of welding equipment, laser-arc hybrid welding technology for pipeline field welding will be available soon.

Numerical simulation of temperature field in laser-arc hybrid welding of wear-resistant steel

Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.

Microstructure and properties of laser-arc hybrid welding of high-strength low-alloy steel

Laser-arc hybrid welding has the characteristics of optimal surface formation and greater penetration;it is extensively used in the welding of plates of medium thickness.However, for hybrid welding of lasers, the welding seam cooling rate is rapid;thus, the welding seam has a higher tendency to significantly harden, which has a negative impact on the weld quality of the high-strength low-alloy(HSLA) steel plates of medium thickness.In this study, laser-arc hybrid welding is performed on the BG890 QL HSLA steel produced by Baoshan Iron & Steel Co.,Ltd.,and the quenching tendency of the welded structure is examined.The results demonstrate that the specific growth direction of the columnar crystal structure of the laser-arc hybrid welded joint is obvious.However, at the center and top of the welded seam, there are equiaxed crystals.The impact properties at room temperature and-40 ℃ of the weld area are 58.0 J and 40.0 J,respectively, and those of the heat-affected zone(HAZ) are 147.0 J and 66.5 J,respectively.The impact performance can meet these requirements.Laser-arc hybrid welding of HSLA steel can yield strong and durable welds and the HAZ structure to meet the requirements of engineering applications.

Enhanced high-temperature mechanical properties of laser-arc hybrid additive manufacturing of Al-Zn-Mg-Cu alloy via microstructure control

Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control.Hydrogen pores became the major defect in the as-deposited and heat-treated specimens.The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treat-ment.High-densityηprecipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy,whereas appeared coarsened and dissolved at 473 K,owing to the rapid diffusion of Zn and Mg.The average 0.2%yield strength(318±16 MPa)and ultimate tensile strength(362±20 MPa)at 473 K af-ter heat treatment were enhanced by approximately 58%and 51%,respectively,compared to those of the as-deposited specimen.In addition,theηprecipitates contributed to lattice distortions and strain fields,which prevented dislocation motion and increased slip deformation resistance at high temper-atures.The as-deposited specimen exhibited intergranular fracture at 473 K,with cracks preferring to propagate along the aggregated eutectics.However,crack propagation proceeded in the sections with more pores in the heat-treated specimen.Our approach may provide a valid option for achieving alu-minum alloys with excellent high-temperature mechanical properties.

激光-电弧复合焊接铝合金的研究进展分析

为早日实现“双碳”目标,轻量化制造是必经之路。铝合金以其低密度、高比强度和可回收利用等优点脱颖而出,并且具备高塑形、优良耐腐蚀能力从而可以广泛应用于各行各业,但因为其特殊的热物理性质及复杂的合金化学成分,使其焊接过程中极易出现气孔、热裂纹等焊接缺陷,其焊接难题限制了铝合金在轻量化之路的进一步发展。激光-电弧复合焊接技术结合激光焊接技术与电弧焊接技术的优势,以其大焊接熔深、高焊接效率、高焊接质量著称,并逐渐成为铝合金高效优质焊接的重要熔焊工艺。为掌握铝合金激光-电弧复合焊的研究现状,本文首次通过文献计量学的方法定量分析了Web of Science(WoS)数据库中1995—2021年已发表的该领域的学术论文,并通过使用VOSviewer软件对WoS数据库数据进行了可视化处理。结果表明,焊接接头、微观组织、热影响区、力学性能及激光与电弧的相互作用为研究热点,因此本文从上述领域对铝合金的激光-电弧复合焊接进行了总结与分析,并结合激光-电弧复合焊接过程中的在线监测技术与新型激光在复合焊中的应用展开讨论分析,得出激光-电弧复合焊接铝合金中接头类型的选取,微观组织的分布,力学性能的提升措施及复合热源的相互作用机制。旨在为后续研究激光-电弧复合焊接铝合金提供参考。最后,基于当下的研究现状,本文提出了该领域面临的挑战及未来工作展望。

基于摆动激光扫描的GMAW焊缝成形调控

将摆动激光与GMAW工艺复合,利用“8”字形摆动激光扫描液态熔池,对其温度场和流场进行调控,以改变熔池温度梯度,主动调控熔池流动以改善焊缝成形.在6061铝合金板材表面进行堆焊试验,重点探究了光丝间距、摆动幅度、激光功率对于焊缝成形的影响,采用高速摄像机拍摄激光扫描熔池过程.结果表明,摆动激光扫描可以有效抑制成形缺陷的发生,当摆动激光扫描熔池中部时可以获得最佳的焊缝成形效果.摆动激光扫描降低了熔池温度梯度分布,同时激光扫描产生的激光蒸发反力可以驱动熔池流动,促进了液态熔池的流动铺展,从而有效抑制了不规则焊缝成形缺陷,减少焊缝内部气孔和裂纹缺陷.调节摆动激光摆幅可以在一定范围内对焊缝宽度进行调控.

焊接方法对铝合金焊接接头微弧氧化色差的影响

目的分析铝合金焊接接头微弧氧化过程中色差产生的原因。方法采用单激光和激光-MIG复合焊2种焊接方法焊接2A12铝合金,利用RGB值定性描述不同焊接试样的色差差异大小,采用金相、SEM和微区XRD观察2A12铝合金单激光和激光-MIG复合焊接头微弧氧化前后的组织、微观形貌和表面物相组成。结果经微弧氧化处理后,2A12铝合单激光焊焊件的焊缝和母材之间无明显色差,2A12铝合金激光-MIG复合焊焊件的焊缝和母材之间存在明显色差,结合金相组织、表面和截面的SEM形貌以及表面EDS和XRD测试分析结果可知,成分和表面熔融物颗粒的大小不同是铝合金焊接接头微弧氧化色差形成的主要原因,焊接接头的组织对铝合金焊接接头微弧氧化色差的产生没有影响。结论单激光焊接接头微弧氧化后的氧化色差较激光-MIG复合焊接头的小;铝合金(2A12)焊接接头产生氧化色差主要是因为焊接接头的成分和表面熔融物颗粒大小不同,而组织对色差无影响。

铂镓合金板材焊接接头组织与力学性能研究

探索及分析铂镓合金板材的焊接工艺,旨在为铂镓合金催化网的焊接提供理论基础。试验制备了Pt-2Ga、Pt-3Ga-2Ru与Pt-5Ga的1 mm厚度板材,采用氩弧焊与不同功率的激光焊对合金进行焊接,对其焊接后的拉伸性能、断口形貌、热影响区宽度、焊接区域的微观组织以及焊接区域元素成分的偏析程度等进行研究。结果表明,Pt-5Ga合金脆性较大无法满足催化网制备条件,Pt-3Ga-2Ru合金的焊接性能优于Pt-2Ga合金,同时晶粒尺寸有大幅减小的趋势。激光焊焊接件的焊接性能优于氩弧焊焊接件,热影响区的宽度更窄,元素的偏析程度也有所减小。将不同功率下的激光焊接试样进行对比后发现:焊接功率设定在350 W时对Pt-3Ga-2Ru合金的拉伸性能最好。

6061铝合金激光摆动-电弧复合焊组织与力学性能分析

对高铁6 mm的6061铝合金进行激光摆动-电弧锁底对接焊,以焊缝熔深与气孔率为指标,借助扫描电子显微镜(scanning election microscope,SEM),电子背散射衍射(electron backscatter diffraction,EBSD)等表征手段分析了摆动频率对焊缝微观组织与力学性能的影响规律.结果表明,当摆动频率升高为250 Hz时,焊缝气孔率降至1%以下,靠近熔合线附近的焊缝区域主要由柱状枝晶组成,而焊缝中心电弧区域主要由等轴枝晶组成,激光摆动频率变化会影响单位周期内光束前进距离,进而影响光束对熔池后方的搅拌能力强弱,随着激光摆动频率的增大,熔池的搅拌作用效果增强,焊缝中心等轴枝晶细化程度明显,晶粒尺寸由68μm降至44μm.当摆动频率为250Hz时,接头的抗拉强度达到最大为229 MPa,约为母材强度的73%,焊缝气孔率的降低和焊缝中心细化的枝晶组织为接头强度提高提供了有利条件.

LEO航天器太阳电池阵激光诱导电弧放电试验与分析

基于太阳电池阵空间电弧放电理论,对纳秒脉冲激光诱导太阳电池阵电弧放电机理进行分析,采用空间放电模拟试验系统,试验研究了低地球轨道(LEO)等离子体环境下纳秒脉冲激光诱导太阳电池阵电弧放电的功率密度阈值及其放电特性。试验结果表明:LEO等离子体环境下激光诱导太阳电池阵电弧放电的功率密度阈值约为1.08×10^(8)W/cm^(2),与无激光诱导相比,放电持续时间增加了20%,且每施加1次纳秒脉冲激光诱导电弧放电概率约为60%。对比分析不同工况下的太阳电池阵损伤效应可得:纳秒脉冲激光诱导电弧放电破坏绝缘层最严重,容易造成太阳电池阵中部分PN结短路失效,其损坏程度远远大于空间环境太阳电池串间电弧放电烧蚀损坏效应和盖玻片表面热应力损伤造成的PN结断路失效。此结论可为航天器太阳电池阵放电试验的措施及试验参数选取提供参考。

厚板窄间隙焊接技术研究现状与应用进展

窄间隙焊接技术已经成为现代工业生产中厚板结构的首选技术,其技术和经济优势决定了它是今后厚板焊接技术发展的主要方向之一,近年来随着科技工作者的不断探索和研发,相继涌现了多种窄间隙焊接方法,文中对电弧焊、激光焊和激光-电弧复合焊等窄间隙焊接制造技术进行了系统阐述,概述了不同热源窄间隙焊接制造过程中的焊接质量、焊接效率的影响因素,归纳了不同热源窄间隙焊的工艺特点及应用领域,结合国内外相关技术的发展现状,总结了窄间隙焊技术面临的问题,提出了后续的发展建议,为相关领域的科研工作者提供参考.

基于BP神经网络薄板P-PAW搭接的间隙自适应工艺参数优化

对大型LNG燃料薄膜舱中1.2 mm厚SUS304L不锈钢板薄板的搭接焊,存在的搭接间隙会带来焊缝成形不良等严重影响船舱安全性的问题。本文通过激光传感器检测搭接间隙变化,设计了不同的峰值电流和焊接速度在不同间隙下的工艺实验,研究了间隙对焊缝成形质量的影响机制;基于BP神经网络建立不同间隙下的脉冲等离子弧焊(P-PAW)的工艺参数和间隙及焊缝成形尺寸之间的拓扑关系模型,通过工艺实验获取模型的训练样本,实现了基于BP神经网络的间隙自适应工艺参数优化系统。结果表明,该系统实现了不同搭接间隙下进行实时工艺参数优化的功能,并对搭接间隙在0~0.6 mm变化时所带来的空洞等缺陷起到了有效的抑制作用,实现了良好的焊接成形一致性控制,提高了在LNG薄膜舱中不锈钢板焊接的自适应能力。

激光-电弧复合增材制造Al-Cu合金T型结构微观组织演变与熔池流动行为分析

在T型结构增材制造过程中,交叉节点处易出现冶金结合不良及重熔缺陷等问题,制约该结构性能的提升。采用激光-电弧复合增材制造技术制备了Al-Cu合金T型结构,对交叉节点处的组织形貌进行了表征,并通过数值模拟分析了节点处熔池内的温度分布以及流动特征。结果表明,在T型结构节点处能够观察到重熔作用所导致的弧形条纹特征,该区域的模拟形貌与实际结果具有良好的一致性;熔池边界处等温线分布较为密集,内部Marangoni对流导致逆时针涡流的形成,最高流速可达0.16 m/s。依据顶层晶粒形态差异,分为顶层节点重熔区(RZI)和顶层热影响区(HAZ)。其中RZI内主要为细小的树枝晶,平均晶粒尺寸相比于HAZ降低了20.8%,内部析出相主要为与α-Al基体呈非共格界面的大尺寸θ(Al_(2)Cu)相;平均显微硬度可达(98.4±6.4)HV_(0.1),相比于未重熔区最高提升约14.0%。

390MPa级船用高强钢激光-MAG复合焊接接头组织与力学性能

对8 mm厚390 MPa级船用高强钢进行了激光-MAG电弧复合焊接,研究了焊接接头焊缝形状和组织特征,分析了焊接接头硬度分布、拉伸性能和冲击性能。结果表明,激光-MAG复合焊接焊缝呈“酒杯”状,热影响区宽度较小。焊接速度为0.8 m/min时,焊缝区组织主要为先共析铁素体、侧板条铁素体、针状铁素体和板条贝氏体;焊接速度达到1.2 m/min以上时,先共析铁素体和侧板条铁素体比例显著减小,针状铁素体和板条贝氏体比例增加。焊接接头硬度均高于母材,没有明显软化区。激光-MAG复合焊接接头具有良好的低温冲击韧性;随着焊接速度增大,焊缝区-40℃和-60℃冲击吸收能量显著增加。

焊接位置对激光-电弧复合焊接底部驼峰的影响

目的通过改变焊接位置来抑制底部驼峰的形成进而降低生产成本。方法使用高速摄像机观察平向焊接和横向焊接2种不同焊接位置下熔池的匙孔和底部驼峰的形成过程,并对底部凸起受到的金属蒸气反冲压力、熔融金属重力以及表面张力进行受力分析。结果在S355J2W耐候钢的激光-电弧复合焊接平焊过程中,受金属蒸气反冲作用力的影响,熔融金属迅速从匙孔底部排出,流入匙孔底部凸起区域,底部凸起的增长速度极快,仅需7.5 ms即可形成大尺寸的驼峰。而在横向焊接中,匙孔前壁凸起数量减少,导致金属蒸气反冲压力减小,匙孔排出的熔融金属量减少,底部凸起的增速减缓,在13.6 ms时才达到最大高度,使驼峰在底部熔池凝固之前难以形成。结论采用横向焊接的方式可以有效避免驼峰的产生,降低生产成本。同时,该方式在焊缝背部成形效果方面也表现良好,为优化焊接工艺提供了重要参考。

Q690钢激光-MIG复合焊焊缝耐腐蚀性能研究

采用焊接效率较高的激光电弧复合焊对Q690钢中厚板(16 mm)进行焊接试验,分析不同激光功率下焊接接头的显微组织和晶粒尺寸的变化,及其开路电位、交流阻抗谱、极化曲线和腐蚀形貌,探讨激光功率对焊缝电化学腐蚀行为的影响规律。结果表明,激光-MIG复合焊焊缝的显微组织由大量针状铁素体和少量侧板条铁素体、粒状贝氏体组成,其中电弧区的针状铁素体、侧板条铁素体含量多于激光区,电弧区的晶粒尺寸比激光区略大;粗晶热影响区显微组织主要由板条马氏体组成。随着激光功率的增加,焊缝中粒状贝氏体含量减少,针状铁素体和侧板条铁素体含量增加。当激光功率从1.5 kW增至2.5 kW时,焊缝的开路电位上升,容抗弧半径增加,极化电阻变大,极化曲线有右移倾向,自腐蚀电流密度下降,耐腐蚀性能提高。但当激光功率增至3.0 kW时,由于组织过于粗大,耐腐蚀性能反而下降。激光功率为2.5 kW时,复合焊焊缝的耐腐蚀性能最佳。

镁基复合材料增材制造技术研究进展

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