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Microstructural formation and mechanical performance of friction stir double-riveting welded Al-Cu joints

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Chinese Journal of Aeronautics 2023年第8期36卷 454-471页

作者： shude ji Zhiqing ZHANG Peng GONG Hua LIU Xiao CUI Yewei ZHANG College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China

A novel friction stir double-riveting welding(FSDRW) technology was proposed in order to realize the high-quality joining of upper aluminum(Al) and lower copper(Cu) plates,and this technology employed a Cu column as a rivet and a specially designed welding tool with a large concave-angle shoulder. The formations, interfacial characteristics, mechanical properties and fracture features of Al/Cu FSDRW joints under different rotational velocities and dwell times were investigated. The results showed that the well-formed FSDRW joint was successfully obtained.The cylindrical Cu column was transformed into a double riveting heads structure with a Cu anchor at the top and an Al anchor at the bottom, thereby providing an excellent mechanical interlocking.The defect-free Cu/Cu interface was formed at the lap interface due to the sufficient metallurgical bonding between the Cu column and the Cu plate, thereby effectively inhibiting the propagation of crack from the intermetallic compound layer at the lap interface between the Al and Cu plates. The tensile shear load of joint was increased first and then decreased when the rotational velocity and dwell time of welding tool increased, and the maximum value was 5.52 k N. The FSDRW joint presented a mixed mode of ductile and brittle fractures.

关键词： Dissimilar Al/Cu metals Friction stir double-riveting welding,Mechanical interlocking Mechanical properties Metallurgical bonding

Achieving High‑Quality Aluminum to Copper Dissimilar Metals Joint via Friction Stir Double‑Riveting Welding

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Acta Metallurgica Sinica(English Letters) 2023年第4期36卷 552-572页

作者： shude ji Xiao Cui Lin Ma Hua Liu Yingying Zuo Zhiqing Zhang College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China

In order to achieve a high-quality joining of aluminum(Al)and copper(Cu)dissimilar metals,a new friction stir doubleriveting welding(FSDRW)with a Cu rod as the rivet was proposed,and the rotating tool with a large concave angle shoulder was specially designed.The results showed that under the thermal–mechanical effect of rotating tool,the Cu rod was deformed to be a double riveting heads structure with a Cu anchor at the upper surface of Al plate and an Al anchor above the lap interface of joint,and these two anchors greatly enhanced the mechanical interlocking of Al/Cu joint.The effective bonding interfaces were formed among the double riveting heads structure,the upper Al plate and the lower Cu plate,which contained the Cu/Cu interface and the Al/Cu interface.The Cu/Cu interface without the kissing bond and the Al/Cu interface with the rationally thin AlCu and Al_(2)Cu intermetallic compounds(IMCs)layers were beneficial to heightening the joint tensile shear strength.The maximum tensile shear load of the FSDRW joint achieved 5.52 kN,and the joint under different plunging depths of rotating tool presented a mixed mode of ductile fracture and brittle fracture.This novel FSDRW technique owns the advantages of strong mechanical interlocking and superb metallurgical bonding,and provides a new approach to acquiring a high-quality Al/Cu dissimilar metals joint.

关键词： Al/Cu dissimilar metals joint Friction stir double-riveting welding Bonding interface Mechanical interlocking Tensile shear load

Active-passive radial-additive friction stir repairing of mechanical hole out of dimension tolerance of AZ31 magnesium alloy

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Journal of Magnesium and Alloys 2023年第9期11卷 3186-3199页

作者： Hua Liu Zhenlei Liu shude ji Yumei Yue Zhibo Dong Changlong Chen College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

In order to avoid the depth increasing of repaired hole and eliminate the super-fine grain band in stir zone by radial-additive friction stir repairing(R-AFSR), a solid-state repairing technique of active-passive radial-additive friction stir repairing(AP-RAFSR) assisted by the truncated cone-shaped filling material was proposed in this study. The mechanical hole out of dimension tolerance of AZ31 magnesium alloy was chosen as the repaired object. The results indicated that the AP-RAFSR process rather than the R-AFSR process avoided the kissing bond in the bottom of the repairing interface under the condition of the tool pin length equal to the height of the standard mechanical hole.The continuously-distributed and large-length super-fine grain bands were eliminated in the stir zone by AP-RAFSR. The maximum tensile and compressive-shear strengths of repaired hole by AP-RAFSR reached 190.6 MPa and 138.9 MPa at 1200 rpm respectively, which were equivalent to 97.7% and 89.6% of those of the standard mechanical hole. This AP-RAFSR process assisted by the truncated cone-shaped filling material provides a new technique to obtain a no-depth-increasing, defect-free and high-strength repaired mechanical hole.

关键词： Active-passive radial-additive friction stir repairing Mechanical hole out of dimension tolerance Numerical simulation Microstructure Mechanical properties

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Journal of Materials Science & Technology 2019年第8期35卷 1712-1718页

作者： shude ji Shiyu Niu jianguang Liu School of Aerospace Engineering Shenyang Aerospace University Shenyang 110136 China Beijing Key Laboratory of Civil Aircraft Structures and Composite Materials Beijing Aeronautical Science & Technology Research Institute of COMAC Beijing 102211 China

The Zn-added ultrasonic assisted friction stir lap welding(UaFSLW) was carried out to improve the quality of dissimilar Al/Mg alloys joint. The effects of ultrasonic power on the joint quality were also investigated.The results indicated that the larger effective lap width and mixing region between Mg and Al(Mg/Al MR) were attained by Zn foil addition and external ultrasonic assistance. Compared with the conventional joint, the finer and better-distributed Mg-Zn IMCs placing the continuous Al-Mg IMCs were formed in the Mg/Al MR of the Zn-added UaFSLW joint. The Zn foil addition and external ultrasonic assistance significantly improved the tensile shear load of the joint, and the load was increased with the increase of the ultrasonic power. The maximum tensile shear load of 7.95 kN was attained, which was 52.6% larger than that of the conventional joint.

关键词： Dissimilar Al/Mg alloys Friction stir lap welding Zn foil Ultrasonic power Microstructures Tensile shear load

Improving friction stir weldability of Al/Mg alloys via ultrasonically diminishing pin adhesion

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Journal of Materials Science & Technology 2018年第10期34卷 1817-1822页

作者： Xiangchen Meng Yanye jin shude ji Dejun Yan Faculty of Aerospace Engineering Shenyang Aerospace University Shenyang 110136 China Department of Industrialization & Informatization Shenyang North Software Institute Shenyang 110000 China Guangdong Provincial Key Laboratory of Advanced Welding Technology for Ships CSSC Huangpu Wenchong Shipbuilding Company Limited Guangzhou510715 China

Formation of intermetallic compounds （IMCs） during friction stir welding （FSW） of alu- minum/magnesium （AI/Mg） alloys easily results in the pin adhesion and then deteriorates joint formation. The severe pin adhesion transformed the tapered-and-screwed pin into a tapered pin at a low welding speed of 30 mm/min. The pin adhesion problem was solved with the help of ultrasonic. The weldability of Al/Mg alloys was significantly improved due to the good material flow induced by mechanical vibration and the fragments of the IMCs on the surface of a rotating pin caused by acoustic streaming, respectively. A sound joint with ultrasonic contained long Al/Mg interface joining length and complex mixture of AI/Mg alloys in the stir zone, thereby achieving perfect metallurgical bonding and mechanical interlocking. The ultrasonic could broaden process window and then improve tensile properties. The tensile strength of the Al/Mg joint with ultrasonic reached 115 MPa.

关键词： Friction stir welding Ultrasonic Aluminum/magnesium alloys Pin adhesion Intermetallic compounds Stationary shoulder

Effect of Welding Technologies on Decreasing Welding Residual Stress of Francis Turbine Runner

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Journal of Materials Science & Technology 2010年第10期26卷 951-956页

作者： shude ji Liguo Zhang Xuesong Liu jianguo Yang School of Aerospace Engineering Shenyang Aerospace University Shenyang 110034 China State Key laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China

On basis of the subsection welding and the local heating's reasonable technological parameters obtained by plane experiment, the welding residual stress field of some Francis turbine runner is regulated and controlled. For the experimental plane with a thickness of 16 mm, the effect of subsection welding on decreasing welding residual stress of the prior welding section is obvious when the distance is less than 50 mm away from the end of latter welding section. For the local heating, the best position, where the effect on decreasing the welding residual stress of plane is best, is 60 mm or so away from the edge of heating area. The experimental results of runner show that the subsection welding can make the residual compressive stress engender in the blade dangerous area while the stress value is greatly influenced by the length of the welding section of blade outlet. The local heating can further decrease the value of residual stress near blade outlet, while the local heating processed after heat treatment is better than that processed before heat treatment.

关键词： Blade Subsection welding Local heating Welding residual stress

Refill friction stir spot welding of 5083-O aluminum alloy

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Journal of Materials Science & Technology 2018年第5期34卷 878-885页

作者： Zhiwu Xu Zhengwei Li shude ji Liguo Zhang State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Faculty of Aerospace Engineering Shenyang Aerospace University

In this work,refill friction stir spot welding（RFSSW） was used to weld 2 mm-thick 5083-O alloy.The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear property.Results showed that a surface indentation of 0.3 mm effectively eliminated the welding defects.Microhardness of the stir zone（SZ） was higher than that of the base material（BM） and the hardness decreased with increasing the heat input during welding.The optimum failure load of 7.72 k N was obtained when using rotating speed of 2300 rpm,plunge depth of 2.4 mm and refilling time of 3.5 s.Three fracture modes were obtained during the lap shear test and all were affected by the hook defect.

关键词： Refill friction stir spot welding Keyhole Secondary phases Microhardness Lap shear failure load

Prediction of Large Structure Welding Residual Stress by Similitude Principles

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Journal of Materials Science & Technology 2009年第6期25卷 861-864页

作者： shude ji Liguo Zhang Xuesong Liu jianguo Yang School of Aerospace Engineering Shenyang Institute of Aeronautical Engineering Shenyang 110034 China State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China

On basis of the similitude principles, the conception of virtual simulative component and the auxiliary value of welding residual stress, which is deduced by the welding conduction theory, the relation of the welding residual stress between the simulative component and the practical component was attained. In order to verify the correctness of the relation, the investigation was done from the view of the welding experiment and the numerical simulation about the simulative component and the practical component. The results show that the distribution of welding residual stress of the simulative component is the same as that of the practical component. The ratio of welding residual stress attained by the experiment or the simulation method between the practical runner and the simulative component was compared with the ratio obtained by the similitude principles. Moreover, the error is less than 10%. This provides a new idea to predict the welding stress distribution of large practical structure by the contractible physical model, which is important for the welding experiment and the numerical simulation. © 2009 by the Editorial Board of Journal of Materials Science and Technology, Shenyang, China. All rights reserved.

关键词： Similitude principles Large welding structure Simulative components Welding residual stress

Effect of Reverse-threaded Pin on Mechanical Properties of Friction Stir Lap Welded Alclad 2024 Aluminum Alloy

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Journal of Materials Science & Technology 2016年第7期32卷 671-675页

作者： Yumei Yue Zhengwei Li shude ji Yongxian Huang Zhenlu Zhou Faculty of Aerospace Engineering. Shenyang Aerospace University Shenyang 110136 China State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Harbin 150001 China

In friction stir welding （FSW）, tool geometry plays an important role in joint quality. In order to improve mechanical properties of friction stir lap welding （FSLW）joint, a tool with a reverse-threaded pin was designed in the present study. Using 2024-T4 aluminum alloy as the research object, tools with the full- threaded pin and reverse-threaded pin were used in FSLW. Results showed that, when using the same parameter combination, FSLW joint using the reverse-threaded pin owned bigger effective sheet thick- ness （EST）, bigger lap width and better lap shear failure strength. Compared with the full-threaded pin, fracture mode of the FSLW joint changed from shear fracture mode to tensile fracture mode when the reverse-threaded pin was used. Fracture morphologies presented ductile fracture.

关键词： Friction stir lap weldingReverse-threaded pinHookFracture position