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Chinese Journal of Mechanical Engineering 2019年第3期32卷 209-217页

作者： P.Dinesh Babu P.Gouthaman P.Marimuthu School of Mechanical Engineering SASTRA Deemed UniversityThanjavur 613401TamilnaduIndia Management Development Centre Ashok LeylandMookandapalliHosurTamilnaduIndia

In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.

关键词： Laser welding Duplex stainless steels Heatsink Cooling medium Distortion Tensile strength Radiography test

Relationship Between Microstructures and Microhardness in High-Speed Friction Stir welding of AA6005A-T6 Aluminum Hollow Extrusions

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 115-126页

作者： Xiang-Qian Liu Hui-Jie Liu Yan Yu Luoyang Ship Material Research Institute Luoyang 471023China State Key Laboratory of Advanced welding and Joining Harbin Institute of TechnologyHarbin 150001China

AA6005 A-T6 aluminum hollow extrusions were friction stir welded at a fixed high welding speed of 2000 mm/min and various rotation speeds.The results showed that the heat-aff ected zone(HAZ)retained the similar grain structure as the base material except some grain coarsening,and the density of dislocations andβ′precipitates were almost unchanged,indicating that the high welding speed inhibited the coarsening and dissolution ofβ″precipitates via fast cooling rate.The thermo-mechanically aff ected zone(TMAZ)was characterized by elongated and rotated grains,in which a low density ofβ′precipitates and the highest density of dislocations were observed.The highest heat input and severest plastic deformation occurring in the nugget zone(NZ)resulted in the occurrence of dynamic recrystallization and a high density of dislocations.Hence,all theβ″precipitates and most of theβ′precipitates dissolved into the matrix,and a fewβ′precipitates were transformed intoβprecipitates.The microhardness was controlled by the precipitation and solution strengthening in the HAZ,by the dislocation and precipitation strengthening in the TMAZ,and by the fine-grain and dislocation strengthening in the NZ.With the increase in rotation speed,the peak and the lowest microhardness value increased monotonously.

关键词： Aluminum hollow extrusions High-speed friction stir welding Grain structure Dislocation and precipitates Microhardness distribution

Microstructure and Mechanical Properties of Cold Metal Transfer welding Similar and Dissimilar Aluminum Alloys

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Acta Metallurgica Sinica(English Letters) 2015年第6期28卷 715-724页

作者： Ahmed Elrefaey Nigel G.Ross LKR Leichtmetallkompetenzzentrum Ranshofen GmbH Austrian Institute of Technology

Integrating structures made from aluminum alloys in automotive industry requires a large amount of joining. As a consequence, the properties of the joints have a significant influence on the overall performance of the whole structure. Robot cold metal transfer welding is a relatively new joining technique and has been used in this work to join 6082-T4 and 5182-O aluminum alloy sheets by using ER5356 and ER4043 filler metals. Microstructure characterization was performed by optical microscopy and energy dispersive X-ray spectroscopy, and the mechanical properties were measured by tensile and hardness tests. A correlation is made between welding variables, mechanical properties and the microstructure of welded joints. Results indicate that robot cold metal transfer welding provides good joint efficiency with high welding speed, good tensile strength, and ductility. Owing to the low heat input of robot cold metal transfer welding process, the heat affected zone microstructure was quite similar to base metals, and weld metal microstructure was the controlling factor of joint efficiency. The best performing were the 5182/5182 joints welded with ER5356 and these had mechanical property coefficients of 100%, 98%, and 85% for yield strength, ultimate tensile strength, and elongation, respectively.

关键词： Aluminum CMT welding Microstructure Tensile property

Effects of welding speed on the multiscale residual stresses in frictionstir welded metal matrix composites

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Journal of Materials Science & Technology 2019年第5期35卷 824-832页

作者： X.X.Zhang L.H.Wu H.ANDra W.M.Gan M.Hofmann D.Wang D.R.Ni B.L.Xiao Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Fraunhofer Institute for Industrial Mathematics Fraunhofer-Platz 1 Kaiserslautern 67663 Germany German Engineering Materials Science Centre Helmholtz-Zentrum Geesthacht D-21502 Geesthacht Germany Heinz Maier-Leibnitz Zentrum (MLZ) Technische Universitat Munchen D-85747 Garching Germany

The effects of welding speed on the macroscopic and microscopic residual stresses(RSes) in friction stir welded 17 vol.% SiCp/2009 Al-T4 composite plates were studied via neutron diffraction and an improved decoupled hierarchical multiscale modeling methods. Measurements showed that the macroscopic and total RSes had the largest variations in the longitudinal direction(LD). Increasing the welding speed led to higher values of measured LD macroscopic and total RSes in the matrix. The welding speed also significantly influenced the distributions and magnitudes of the microscopic RSes. The RSes were predicted via an improved hierarchical multiscale model, which includes a constant coefficient of friction based thermal model. The RSes in the composite plates before friction stir welding(FSW) were computed and then set as the initial states of the FSW process during modeling. This improved decoupled multiscale model provided improved predictions of the temperature and RSes compared with our previous model.

关键词： Metal-matrix composites (MMCs) Friction stir welding Residual/internal stress Neutron diffraction Finite element analysis (FEA) Multiscale simulation

Optimisation of laser welding parameters for welding of P92 material using Taguchi based grey relational analysis

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Defence Technology（防务技术） 2016年第4期12卷 343-350页

作者： Shanmugarajan B. Rishabh SHRIVASTAVA Sathiya P. Buvanashekaran G. welding Research Institute Bharat Heavy Electricals Ltd. Tiruchirappalli 620014 Tamil Nadu India GE India Technology Centre Bangalore India Department of Production Engineering NIT Tiruchirappalli India

Creep strength enhanced ferritic(CSEF) steels are used in advanced power plant systems for high temperature applications. P92(Cr–W–Mo–V)steel, classified under CSEF steels, is a candidate material for piping, tubing, etc., in ultra-super critical and advanced ultra-super critical boiler applications. In the present work, laser welding process has been optimised for P92 material by using Taguchi based grey relational analysis(GRA).Bead on plate(BOP) trials were carried out using a 3.5 k W diffusion cooled slab CO_2 laser by varying laser power, welding speed and focal position. The optimum parameters have been derived by considering the responses such as depth of penetration, weld width and heat affected zone(HAZ) width. Analysis of variance(ANOVA) has been used to analyse the effect of different parameters on the responses. Based on ANOVA, laser power of 3 k W, welding speed of 1 m/min and focal plane at-4 mm have evolved as optimised set of parameters. The responses of the optimised parameters obtained using the GRA have been verified experimentally and found to closely correlate with the predicted value.? 2016 China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.

关键词： Laser welding Optimisation Taguchi P92

Microstructure and Mechanical Properties of RAFM-316L Dissimilar Joints by Friction Stir welding with Different Butt Joining Modes

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 135-146页

作者： Bin He Lei Cui Dong-Po Wang Hui-Jun Li Chen-Xi Liu Tianjin Key Laboratory of Advanced Joining Technology School of Materials Science and EngineeringTianjin UniversityTianjin 300354China

Dissimilar welded joints of reduced activation ferritic/martensitic(RAFM)steel and 316 L austenitic stainless steel were prepared by friction stir welding with different butt joining modes and welding parameters.The weld quality of the joint was improved by placing the 316 L steel on the advancing side and the RAFM steel on the retreating side,and using a relatively high rotational speed of 400 rpm.The microstructure of the stir zone on the 316 L steel side consisted of single-phase austenite,and the microstructure of the stir zone on the RAFM steel side mainly consisted of lath martensite and equiaxed ferrite.A mechanical mixture of the two steels and diffusion of Cr and Ni could be detected near the bonding interface.Diffusion of Ni from the 316 L steel to the RAFM steel resulted in the formation of a dual-phase structure consisting of austenite and ferrite.The as-welded joints showed good strength and ductility at room temperature and 550°C,which were nearly equal to those of the 316 L base material.The heat-affected zone on the RAFM side had the lowest impact toughness throughout the weld with a value of 13.2 J at-40°C,~52%that of the RAFM base material.

关键词： Friction stir welding Dissimilar joint RAFM steel 316L steel Microstructures Mechanical properties

Effect of Zener-Hollomon Parameter on Microstructure and Mechanical Properties of Copper Subjected to Friction Stir welding

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Acta Metallurgica Sinica(English Letters) 2020年第2期33卷 319-326页

作者： Nan Xu Ruo-Nan Feng Wen-Feng Guo Qi-Ning Song Ye-Feng Bao College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213022China

In this work,the influence of the Zener-Hollomon(Z)parameter on the microstructure and mechanical properties of copper subjected to friction stir welding(FSW)was investigated.Liquid N2 cooling was conducted to control the cooling rate after the FSW.The obtained results demonstrate that the Z parameter was dependent on the tool rotation rate during the FSW,i.e.,a higher tool rotating rate resulted in a lower Z parameter.The grain size in the stir zone decreased with the increase in the Z parameter.The relationship between the yield strength and the Z parameter is established asσ0.2=σ0+kZn.This relationship exhibited two different plots under the conditions of air cooling and liquid N2 cooling.Even at a similar Z parameter,a significant yield strength difference occurred because massive dislocations,which were caused by the prevention of the post-annealing effect,were maintained in the stir zone.This study suggests that the influence of the post-annealing effect should not be neglected when analyzing the relationship between the Z parameter,micro structure,and mechanical properties.

关键词： Copper Friction stir welding Microstructure Mechanical properties

Experimental and numerical investigations of bonding interface behavior in stationary shoulder friction stir lap welding

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Journal of Materials Science & Technology 2019年第1期35卷 192-200页

作者： Q.Wen W.Y.Li W.B.Wang F.F.Wang Y.J.Gao V.Patel State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University China FSW Center China Academy of Launch Vehicle Technology Beijing Institute of Astronautical Systems Engineering Capital Aerospace Machinery Company Pandit Deendayal Petroleum University

Stationary shoulder friction stir lap welding(SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian(CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side(RS) and the advancing side(AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.

关键词： Stationary shoulder friction stir lap welding Coupled Eulerian-Lagrangian Temperature field Material distribution Equivalent plastic strain

Effect of retained austenite and nonmetallic inclusions on the thermal/electrical properties and resistance spot welding nuggets of Si-containing TRIP steels

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International Journal of Minerals,Metallurgy and Materials 2019年第1期26卷 52-63页

作者： V.H.Vargas I.Mejía V.H.Baltazar-Hernández C.Maldonado Metallurgy and Materials Research Institute Universidad Michoacana de San Nicolás de Hidalgo Edificio "U" Ciudad Universitaria Materials Science and Engineering Program Autonomous University of Zacatecas

Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.

关键词： transformation-induced plasticity steel retained austenite non-metallic inclusions magnetic saturation electrical properties thermal properties resistance spot welding nugget

On the heterogeneous microstructure development in the welded joint of 12MnNiVR pressure vessel steel subjected to high heat input electrogas welding

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Journal of Materials Science & Technology 2019年第8期35卷 1747-1752页

作者： Yang Shen Ju Leng Cong Wang School of Metallurgy Northeastern University Shenyang 110819 China Shenyang NEU New Industrial Technology Research Institute Co. LTD Shenyang 110819 China

Microstructure features of 12 MnNiVR pressure vessel steel welded joint deposited by the high heat input electrogas welding have been systematically investigated. It is revealed that the welded joint is featured by a heterogeneous juxtaposition. The coarse grained heat-affected zone(CGHAZ) primarily consists of lath bainites and minor granular bainites. The fine grained heat-affected zone(FGHAZ) is dominated by polygonal ferrites, pearlites, and fine cementite particles. Moreover, electron backscatter diffraction results further demonstrate that the CGHAZ is populated by coarse prior austenite grains(PAGs) with high frequency(61.3%) of low angle grain boundaries(LAGBs). On the other hand, the FGHAZ is filled with fine PAGs with a lower frequency(19.6%) of LAGBs. Such microstructural differences may likely contribute to differed mechanical properties for samples tested at designed positions.

关键词： 12MnNiVR pressure vessel steel Electrogas welding High heat input Electron backscatter diffraction