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laser welding process and strength enhancement of carbon fiber reinforced thermoplastic composites and metals dissimilar joint:A review

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Chinese Journal of Aeronautics 2023年第12期36卷 13-31页

作者： Junke JIAO Jihao XU Chenghu JING Liyuan SHENG Haolei RU Hongbo XIA School of Mechanical Engineering Yangzhou UniversityYangzhou 225009China PKU-HKUST ShenZhen-HongKong Institution Shenzhen 518057China Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China

Carbon fiber reinforced thermoplastic composites(CFRTP)and metals hybrid structures have been widely used in aircraft lightweight ***,due to the significant difference in physical and chemical properties between CFRTP and metals,there are lots of challenges to connect them with high *** welding has a good application prospect in CFRTP and metals connection,and a significant research progress has been made in the exploration of CFRTP-metal laser joining mechanism,joining process optimization,joining strength improvement and joining defects ***,there are still some problems need to be solved for this technology *** this paper,the research progress of CFRTP-metal laser joining was summarized in three major aspects:theoretical modeling and simulation analysis,process exploration and parameter optimization,joint performance improvement and process ***,problems and challenges of this technology were discussed,and the outlook of this research was provided.

关键词： Carbon fiber reinforced thermoplastic composite and metal hybrid joints Defects controlling laser welding Numerical simulation

laser welding of 6061 aluminum alloy sheet with surfactant

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China welding 2011年第4期20卷 66-70页

作者：石文玲杨立军王金杰王小博 School of Materials Science and Engineering Tianjin University Tianjin300072. Tianjin Key Laboratory of Advanced Joining Technology Tianjin University Tianjin 300072.

Aluminum alloy shows low absorption to laser for its essential high reflection property. In this paper, an active laser welding process is adopted to weld 6061 aluminum alloy with the halide suocactant coated on sheet surface to improve the welding quality. The sheets with surfactant are welded under a series of welding parameters of laser power and welding speed while the plasma plumes in the welding process are recorded by high-speed camera. Then a metaUographic analysis and a transverse tensile test are implemented to assess the sheet butt joint property. The experiments show that the weld depth is deepened and the plasma plume is smaller with surfactant. A well formed weld of 1 mm-thickness sheet of 6061 aluminum alloy can be obtained under laser power of 920 W, welding speed of 7 mm/s, zero defocusing-amount and an argon shielding gas flow of 30 L/min.

关键词： surfactant 6061 aluminum alloy laser welding plasma plume

Effect of laser welding Process Parameters on Microstructure and Mechanical Properties on Butt Joint of New Hot-Rolled Nano-scale Precipitation-Strengthened Steel

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Acta Metallurgica Sinica(English Letters) 2014年第3期27卷 521-529页

作者： Min Zhang Xiaonan Wang Guangjiang Zhu Changjun Chen Jixin Hou Shunhu Zhang Hemin Jing laser Processing Research Center School of Mechanical and Electrical Engineering Soochow University Shagang School of Iron and Steel Soochow University School of Materials Science & Engineering Anhui University of Technology

A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.

关键词： laser welding Microstructure Mechanical properties Microalloyed steel

Microstructure and properties of 1100 MPa grade low-carbon hot-rolled steel by laser welding

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Journal of Iron and Steel Research International 2018年第2期25卷 228-234页

作者： Chen Dong Ai-min Zhao Xi-tao Wang Qi-hang Pang Hui-bin Wu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083 China Engineering Research Institute University of Scienceand Technology Beijing Beijing 100083 China

The microstructure and mechanical properties of the butt joint of 1100 MPa grade hot-rolled low-carbon steel by laser welding were investigated by scanning electron microscopy, micro-hardness and tensile tests. The yield strength and tensile strength of the laser welded joint reached 100.2 and 99.5% of the base material （BM）, respectively. However, the elongation of the welded joint only reached about 60% of BM. The lowest and highest hardness areas both existed in the incomplete recrystallization zone. The width of the softened area of the welded joint is about 240-260 pro. The element distribution has no obvious change for C, Cr, Si, Mn, Ti, etc.

关键词： Hot-rolled steel laser welding Microstructure Mechanical property Element distribution

Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment

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Journal of Magnesium and Alloys 2022年第10期10卷 2788-2800页

作者： Jie Ning Suck-Joo Na Lin-Jie Zhang Xiang Wang Jian Long Won-Ik Cho State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China BIAS-Bremer Institut für angewandte Strahltechnik GmbH Klagenfurter Straße 528359 BremenGermany

The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor *** 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 *** AZ31magnesium(Mg)alloy was used as the test *** test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal *** 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 ***,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 *** LW in subatmospheric environment,the weld penetration can be further greatly increased through power ***,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 ***,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was *** 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.

关键词： laser welding Subatmospheric environment Power modulation Highly reflective materials Thermal efficiency Stability

Multi-physics multi-scale simulation of unique equiaxed-to-columnar-to-equiaxed transition during the whole solidification process of Al-Li alloy laser welding

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Journal of Materials Science & Technology 2024年第4期171卷 235-251页

作者： Chu Han Ping Jiang Shaoning Geng Liangyuan Ren School of Mechanical Science and Engineering Huazhong University of Science&Technology(HUST)Wuhan430074China

In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-Li *** accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were *** was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-Li alloy laser *** results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(BM)de-creased as the nucleation rate *** the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite *** the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the ***,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the ***,how equiaxed grain bands develop was *** equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar *** predicted results were in good agreement with experimental measurements and observations.

关键词： laser welding Al-Li alloy Equiaxed-to-columnar-to-equiaxed transition Multi-physics multi-scale model Multicomponent alloys 3D phase-field model

Effect of laser welding on Properties of Dissimilar Joint of Al-Mg-Si and Al-Mn Aluminum Alloys

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Journal of Materials Science & Technology 2010年第3期26卷 276-282页

作者： C.C.Chang C.P.Chou S.N.Hsu G.Y.Hsiung J.R.Chen Department of Mechanical Engineering National Chiao-Tung University National Synchrotron Radiation Research Center Department of Biomedical Engineering and Environmental Sciences National Tsing-Hua University

This study discusses the welding properties for the components of an aluminum-alloy ultra-high vacuum chamber and beam position monitor （BPM）.The welding parameters include the modes of laser output （pulsed wave and continuous wave）,welding speed,shield gas flow,welding bead structure,and focusing *** results showed that the welding defect rate of the pulsed wave type was larger than that of the continuous wave *** crack in the welding bead reduced with decreasing welding *** fusion penetration of the welding bead was higher when the focusing distance was long enough to deepen into the welding *** morphology during the experimental process revealed the proper flow of shield *** adaptability design of the welding bead structure in the preceding processes had more effect on overall welding structure and morphology.

关键词： laser welding Aluminum alloy Ultra-high vacuum Beam position monitor (BPM)

Learning semantic-specific visual representation for laser welding penetration status recognition

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Science China(Technological Sciences) 2022年第2期65卷 347-360页

作者： LIU TianYuan BAO JinSong ZHENG HangBin WANG JunLiang YANG ChangQi GU Jun Institute of Intelligent Manufacturing College of Mechanical EngineeringDonghua UniversityShanghai 201600China Shanghai Spaceflight Precision Machinery Institute Shanghai 201600China Shanghai Institute of laser Technology Shanghai 200235China

The degree of penetration can directly reflect the forming quality of laser welding. The fine-grained feature of the molten pool/keyhole image brings challenges to the vision-based laser welding penetration status recognition. In this paper, a novel knowledge-and-data-hybrid driven recognition model is proposed for solving the problem of difficult learning of discriminative visual features of molten pool/keyhole images. In addition, a label semantic attention mechanism(LSA) is designed with three modules: representation of image visual feature, representation of labels semantic feature, and generation of label semantic attention. For learning discriminative features in visual space, LSA uses discriminative information in label semantics to guide the convolutional neural network. The experimental results show that the proposed LSA method has faster convergence and higher accuracy than the traditional attention mechanism. Further comparative experiments reveal that LSA is less dependent on the amount of training data and model complexity. The results of visualization experiments show that the visual features learned by the proposed method are more discriminative.

关键词： label semantic attention mechanism word embedding convolutional neural network laser welding penetration status

Heat transfer and fluid flow and their effects on the solidification microstructure in full-penetration laser welding of aluminum sheet

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Journal of Materials Science & Technology 2020年第11期42卷 50-63页

作者： Shaoning Geng Ping Jiang Xinyu Shao Lingyu Guo Xuesong Gao The State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science Technology430074 WuhanChina Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong University250061 JinanChina

Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser *** paper develops a three-dimensional numerical model to understand the multi-physical processes such as heat transfer,melt convection and solidification behavior in full-penetration laser welding of thin 5083 aluminum *** parameters including temperature gradient G and solidification rate R,and their combined forms are evaluated to interpret solidification *** predicted weld dimensions and the microstructure morphology and scale agree well with *** indicate that heat conduction is the dominant mechanism of heat transfer in weld pool,and melt convection plays a critical role in microstructure *** mushy zone shape/size and solidification parameters can be modulated by changing process *** structures form because of the low G/R *** scale of dendritic structures can be reduced by increasing GR via decreasing heat *** columnar to equiaxed transition is predicted quantitatively via the process related G^3/*** findings illustrate how heat transfer and fluid flow affect the solidification parameters and hence the microstructure,and show how to improve microstructure by optimizing the process.

关键词： laser welding Heat transfer Fluid flow Solidification microstructure Aluminum