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Microstructure Evolution of Heat‑Affected Zone in Submerged Arc Welding and Laser Hybrid Welding of 690 MPa High Strength Steel and its Relationship with Ductile–Brittle Transition Temperature

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Acta Metallurgica Sinica(English Letters) 2023年第4期36卷 623-636页

作者： Xuelin Wang Wenjuan Su Zhenjia Xie Xiucheng Li Wenhao Zhou Chengjia Shang Qichen Wang Jian Bai Lianquan Wu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Guangdong Laboratory for Materials Science and Technology(Yangjiang Advanced Alloys Laboratory) Yangjiang BranchYangjiang 529500China Xiangtan Iron and Steel Co. Ltd of Hunan ValinXiangtan 411101China CIMC Raffles Offshore Limited Longkou 265700China CIMC Offshore Engineering Institute Limited Yantai 264670China Yangjiang Yichuan Metal Technology Co. LtdYangjiang 529533China

The comparative study of submerged arc Welding(SAW)and laser hybrid Welding(LHW)was carried out for a 690 MPa high strength steel with thickness of 20 mm.Microstructure and ductile–brittle transition temperature(DBTT)evolution in welded zone were elucidated from the aspect of crystallographic structure,particularly,digitization and visualization of 24 variants.The impact toughness of each micro zone in LHW joint is better than that of SAW,in which the DBTT of equivalent fusion line and heat-affected zone(HAZ)can reach−70 and−80℃,while that of SAW is only−50℃.LHW technology induces narrowing of the HAZ and refining of the microstructure obtained in weld metal and HAZ.Meanwhile,the austenite grain size and transformation driving force in the coarse grained heat-affected zone(CGHAZ)are reduced and increased,respectively.It makes variant selection mechanism occurring in CGHAZ of LHW dominate by close-packed plane grouping,which promotes lath bainite formation with high density of high angle grain boundary,especially block boundary dominated by V1/V2 pair.While for SAW,the lower transformation driving force inferred from the large amount of retained austenite in CGHAZ induces Bain grouping of variants,and thus triggers the brittle crack propagating straightly in granular bainite,resulting in lower impact toughness and higher DBTT.

关键词： High strength steel Welding Microstructure Variant selection Ductile-brittle transition temperature

Influence of parameters on the microstructure of a duplex stainless steel joint welded by a GMAW Welding process

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Progress in Natural Science:Materials International 2022年第4期32卷 415-423页

作者： Sandra Chacón-Fernández Antonio Portolés García Gerardo Romaní Labanda Universidad Politécnica de Madrid Escuela Técnica Superior de Ingenieros Industriales UPM

Duplex stainless steels(DSSs) are widely used in industry for their desirable properties. Any fusion Welding technique modifies the microstructure and, consequently, the properties of the material. This paper presents a parametric study of the variables that determine the energy contribution(current, voltage and Welding speed) and the structural modifications produced during gas metal arc Welding. The analysis comprises metallographic study,phase balance, dimensioning of the weld beads and tensile and hardness tests. The influence of the variables studied on the thermal cycles obtained(temperatures reached and cooling rate) was determined by using a finite element model. The results showed that, in addition to the indicated parameters, the parameter power transfer per volume(W/m3) and the geometry in the bead must be controlled due to their influence on the heat flow distribution and phase balance.

关键词： Welding Heat input GMAW Duplex stainless steels (DSS) Finite element model (FEM)

Comparison of feasibility,microstructure and performance of hybrid laser arc,activated flux tungsten inert gas and friction stir Welding for thick plate of innovative ultra-pure ferritic stainless steel

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Journal of Iron and Steel Research(International) 2022年第4期29卷 665-676页

作者： Jian Han Lian-meng Liu Xin-ya Chen Min-fang Chen Lei Cui Yang-chuan Cai Yin-bao Tian School of Materials Science and Engineering Tianjin University of TechnologyTianjin 300384China School of Materials Science and Engineering Tianjin UniversityTianjin 300072China

An innovative grade of ferritic stainless steel,ultra-pure 18Cr–2Mo thick plate,was designed and produced for special industrial application.In order to maintain its mechanical properties after joining,three advanced joining methods,hybrid laser arc Welding,activated flux tungsten inert gas Welding and friction stir Welding,were selected and conducted to connect the thick plates.The feasibility of three joining methods,the microstructure and mechanical properties were compared,and the results have demonstrated that the sound joint was successfully produced using the selected parameters through friction stir Welding.The obtained hardness and impact toughness of the weld zone were satisfying.In terms of activated flux tungsten inert gas Welding,the crack will be created due to microstructural brittleness.And as for hybrid laser arc Welding,the weld zone is narrow,and the addition of wire during Welding for the top weld metal area leads to higher formation ratio of low-angle grain boundaries,which is beneficial to performance of the joint.However,there is still a weak area in the fusion line of the welded joint.The result has illustrated that the Welding of innovative ultra-pure ferritic stainless steel thick plate by friction stir Welding is feasible.

关键词： Ultra-pure ferritic stainless steel Hybrid Welding Activated flux tungsten inert gas Friction stir Welding Microstructural evolution Mechanical property

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Journal of Materials Science & Technology 2021年第26期85卷 95-105页

作者： Nana Kwabena Adomako Giseung Shin Nokeun Park Kyoungtae Park Jeoung Han Kim Department of Materials Science and Engineering Hanbat National UniversityYuseong-guDaejeon34158Republic of Korea Department of Materials Science and Engineering Pusan National UniversityGeumjeong-guBusan46241Republic of Korea School of Materials Science and Engineering Yeungnam University280 Daehak-roGyeongbuk38541Republic of Korea Rare Metal R&D Group Korea Institute of Industrial TechnologyIncheon21999Republic of Korea

High entropy alloys(HEAs)have superior mechanical properties that have enabled them to be used as structural materials in nuclear and aerospace applications.As a dissimilar joint design is required for these applications,we created a dissimilar joint between CoCrFeMnNi-HEA and duplex stainless steel(DSS)through laser beam Welding;a technique capable of producing a sound joint between the two materials.Micro structure examination using SEM/EBSD/XRD analysis revealed that the weld metal(WM)exhibits an FCC phase regardless of the postweld heat treatment(PWHT)temperature(800 and 1000℃)without forming detrimental intermetallic compounds or microsegregation.The heat-affected zone of the CoCrFeMnNi-HEA showed CrMn oxide inclusions while that of the DSS showed no inclusions.Moreover,a lower hardness was recorded by the WM compared to the base metal after Welding.After PWHT,the hardness of the WM,CoCrFeMnNi-HEA,and DSS decreased with an increase in the PWHT temperature.However,the decrease in the hardness of the HEA was more significant than in the WM and DSS.The cause for this reduction in hardness was attributed to recrystallization and grain growth.In addition,a strength of 584 MPa with low ductility was recorded after Welding.The obtained strength was lower than that of the BMs,but comparable to that of the welded CoCrFeMnNi-HEA.The application of PWHT resulted in over a 20%increment in ductility,with only a marginal reduction in strength.The defo rmation mechanism in the as-weld joint was mainly dominated by dislocation while that for the PWHT joint was twinning.We propose laser beam offset Welding as a technique to improve the mechanical properties of the dissimilar joint,which will be the subject of future studies.

关键词： High entropy alloys Welding Duplex stainless steel Post-weld heat treatment

Semi-transparent,flexible,and electrically conductive silicon mesh by capillarity-driven Welding of vapor-liquid-solid-grown nanowires over large areas

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Nano Research 2020年第5期13卷 1465-1471页

作者： Thomas A.Celano Seokhyoung Kim David J.Hill James F.Cahoon Department of Chemistry University of North Carolina at Chapel HillChapel HillNC 27599-3290USA

Bottom-up synthesis of semiconductor nanowires(NWs)by the vapor-liquid-solid(VLS)mechanism has enabled diverse technological applications for these nanomaterials.Unlike metallic NWs,however,it has been challenging to form large-area interconnected NW networks.Here,we generate centimeter-scale meshes of mechanically and electrically interconnected Si NWs by sequentially growing,collapsing,and joining the NWs using a capillarity-driven Welding mechanism.We fabricate meshes from VLS-grown NWs ranging in diameter from 20 to 100 nm and find that the meshes are three-dimensional with a thickness ranging from^1 to^10 microns depending on the NW diameter.Optical extinction measurements reveal that the networks are semi-transparent with a color that depends on the absorption and scattering characteristics of individual NWs.Moreover,active voltage contrast imaging of both centimeter-and micron-scale meshes reveals widespread electrical connectivity.Using a sacrificial layer,we demonstrate that the mesh can be liberated from the growth substrate,yielding a highly flexible and transparent film.Electrical transport measurements both on the growth substrate and on liberated,flexible films reveal electrical conduction across a centimeter scale with a sheet resistance of^160-180 kΩ/square that does not change significantly upon bending.Given the ability to encode complex functionality in semiconductor NWs through the VLS process,we believe these meshes of networked NWs could find application as neuromorphic memory,electrode scaffolds,and bioelectronic interfaces.

关键词： semiconductor nanowire conductive network flexible electronics Welding thermal annealing active-voltage contrast

AR-assisted robot Welding programming

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Advances in Manufacturing 2020年第1期8卷 40-48页

作者： S.K.Ong A.Y.C.Nee A.W.W.Yew N.K.Thanigaivel Department of Mechanical Engineering Faculty of EngineeringNational University of SingaporeSingapore

Robotic Welding demands high accuracy and precision.However,robot programming is often a tedious and time-consuming process that requires expert knowledge.This paper presents an augmented reality assisted robot Welding task programming(ARWP)system using a user-friendly augmented reality(AR)interface that simplifies and speeds up the programming of robotic Welding tasks.The ARWP system makes the programming of robot Welding tasks more user-friendly and reduces the need for trained programmers and expertise in specific robotic systems.The AR interface simplifies the definition of a Welding path as well as the Welding gun orientation,and the system;the system can locate the Welding seam of a workpiece quickly and generate a viable Welding path based on the user input.The developed system is integrated with the touch-sensing capability of Welding robots in order to locate the Welding path accurately based on the user input,for fillet Welding.The system is applicable to other Welding processes and methods of seam localization.The system implementation is described and evaluated with a case study.

关键词： Augmented reality(AR) Robot programming Welding Seam tracking

Effect of tool rotational speed on the particle distribution in friction stir Welding of AA6092/17.5 SiCp-T6 composite plates and its consequences on the mechanical property of the joint

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Defence Technology（防务技术） 2020年第2期16卷 381-391页

作者： Uttam Acharya Barnik Saha Roy Subhash Chandra Saha Department of Mechanical Engineering National Institute of Technology AgartalaBarjalaJiraniaWest Tripura799046India

This study investigates the effect of tool rotational speed(TRS)on particle distribution in nugget zone(NZ)through quantitative approach and its consequences on the mechanical property of friction stir welded joints of AA6092/17.5 SiCp-T6 composite.6 mm thick plates are welded at a constant tool tilt angle of 2°and tool traverse speed of 1 mm/s by varying the TRS at 1000 rpm,1500 rpm and 2000 rpm with a taper pin profiled tool.Microstructure analysis shows large quantity of uniformly shaped smaller size SiC particle with lower average particle area which are homogeneously distributed in the NZ.The fragmentation of bigger size particles has been observed because of abrading action of the hard tool and resulting shearing effect and severe stress generation due to the rotation of tool.The particles occupy maximum area in the matrix compared to that of the base material(BM)due to the redistribution of broken particles as an effect of TRS.The migration of particles towards the TMAZ-NZ transition zone has been also encountered at higher TRS(2000 rpm).The microhardness analysis depicts variation in average hardness from top to bottom of the NZ,minimum for 1500 rpm and maximum for 2000 rpm.The impact strength at 1000 rpm and 1500 rpm remains close to that of BM(21.6 J)while 2000 rpm shows the accountable reduction.The maximum joint efficiency has been achieved at 1500 rpm(84%)and minimum at 1000 rpm(68%)under tensile loading.Fractographic analysis shows mixed mode of failure for BM,1000 rpm and 1500 rpm,whereas 2000 rpm shows the brittle mode of failure.

关键词： Friction stir Welding Aluminium matrix composite Tool rotational speed Particle distribution Mechanical property

Joint formation mechanism of high depth-to-width ratio friction stir Welding

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Journal of Materials Science & Technology 2019年第7期35卷 1261-1269页

作者： Yongxian Huang Yuming Xie Xiangchen Meng Junchen Li Li Zhou State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology

High depth-to-width ratio friction stir Welding is an attractive method for the joining demands of alum inum profiles, which is sparked with its extrem ely low heat input and high mechanical performance. In this study, the joint form ation mechanism was studied by a num erical model of plastic flow combined with experim ental approaches. A fluid-solid-interaction algorithm was proposed to establish the coupling model, and the material to be welded was treated as non-New tonian fluid. The thread structure and the milling facets on tool pin prom oted drastic turbulence of material. The thread structure converged the plasticized material by its inclined plane, and then drove the attached material to refill the welds. The milling facets brought about the periodic dynamic material flow. The thread structure and the milling facets increased the strain rate greatly under the extremely low heat input, which avoided the Welding defects. The condition of the peak tem perature of 648 K and the strain rate of 151 s^-1 attributed to the lowest coarsening degree of precipitate. The tensile strength of the joint reached 265 MPa, equivalent to 86% of base material. The amelioration via the material flow model inhibits the Welding defects and optimizes the param eter intervals, providing references to extracting process-structure-property linkages for friction stir Welding.

关键词： Friction stir Welding Joint formation Material flow Al-Mg-Si alloy 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