Effect of Welding Parameters on Tensile Properties and Fatigue Behavior of Friction Stir Welded 2014-T6 Aluminum Alloy

The present work describes the effect of welding parameters on the tensile properties and fatigue behaviour of 2014-T6 aluminum alloy joints produced by friction stir welding (FSW). Characterization of the samples has been carried out by means of microstructure, microhardness, tensile properties and fatigue behaviors. The hardness in the softened weld region decreases with decreasing the welding speed. Irrespective of the tool rotation speeds, the best tensile and fatigue properties were obtained in the joints with the welding speed of 80 mm/min. The joint welded with a rotating speed of 1520 rpm at 80 mm/min has given a highest tensile and fatigue properties. The fatigue behaviors of the joints are almost consistent with the tensile properties, especially elongations. Higher ductility in FSW joints made the material less sensitive to fatigue. The location of tensile fractures of the joints is dependent on the welding parameters. On the other hand, the fatigue fracture locations change depending on the welding parameters and stress range. In addition, a considerable correlation could not be established in between heat indexes and mechanical properties of FSW 2014-T6 joints under the investigated welding parameters.     

SPCC冷轧钢胶焊连接工艺研究及数值模拟

 为了研究胶焊工艺对接头力学性能的影响,并分析胶焊接头的温度场演变规律,针对1.5 mm厚的SPCC冷轧钢薄板,开展胶接点焊和电阻点焊的正交试验,并应用极差和方差分析得到最佳工艺参数,借助材料性能试验机对两种接头进行单向静拉伸试验获得接头的失效载荷,对比分析点焊和胶焊接头的力学性能,建立胶焊接头的仿真模型,分析接头熔核区温度场的演变规律,采用超声波C扫描成像检测熔核直径。结果表明,影响胶焊接头拉剪载荷的主、次因素依次为焊接电流、焊接时间、电极压力;胶焊接头和点焊接头的平均失效载荷分别为11 071.12和10 179.72 N,胶层的引入提高了接头的失效载荷;随着焊接时间的增加,熔融的金属液增多,熔核沿着径向和轴向呈椭圆形扩张,熔核中心的径向温度均高于轴向温度,模拟获得的熔核尺寸与超声C扫描测得熔核直径分别为6.17、5.61 mm。     

Microstructural and Mechanical Characterization of as Weld and Aged Conditions of AA2219 Aluminium Alloy by Gas Tungsten Arc Welding Process

In this article, Welding of AA2219 aluminium alloy using Gas tungsten arc welding process (GTAW) and evaluation of metallurgical, mechanical and corrosion properties of the joints are discussed. The weld samples were subjected to ageing process at the temperature range of 195°C for a period of 5 h to improve the properties. AA2219 aluminium plates of thickness of 25 mm were welded using gas tungsten arc welding (GTAW) process in double V butt joint configuration. The input parameters considered in this work are welding current, voltage and welding speed. Tensile strength and hardness were measured as performance characteristics. The variation in the properties were justified with the help of microstructures. The same procedures were repeated for post weld heat treated samples and a comparison was made between as weld condition and age treated conditions. The post weld heat samples had better tensile strength and hardness values on comparing with the as weld samples. Fracture surface obtained from the tensile tested specimen revealed ductile mode of failure.     

The Effect of Cutting Speed and Depth of Cut on Surface Roughness During Machining of Austempered Ductile Iron

In this paper, the influence of process parameters on microstructural characteristics & mechanical properties of AZ80A Mg alloy during friction stir welding (FSW) are investigated in a detailed manner. The tensile fracture surfaces obtained from successfully fabricated joints are subjected to tensile tests and microstructural investigations were done using scanning electron microscope. From the experimental results, the joints produced under a 5 kN axial force value at 1000 rpm and at a feed rate of 1.5 mm/min were found to exhibit superior mechanical properties and metallurgically defect free weldments when compared with other joints. The chemical compositions of these defect free joints were analyzed using energy dispersive spectrometry. Moreover, ideal level of heat generation, uniform flow of the plasticized material and formation of fine grain structure with uniform distribution in the FSW zone were found to be the main reasons for these superior mechanical properties and flawless joints.     

Investigation on Metallurgical Structure and Mechanical Properties of Dissimilar Al 2024/Cu FSW T-joints

In this research, T-joining of AA2024-T4 and commercially pure copper were performed successfully using friction stir welding. Effect of welding parameters on metallurgical and mechanical characteristics of the joints was studied. For this purpose, tensile strength, microhardness, and macro- and microstructures of the joints were investigated. Also, the fracture surfaces were examined using XRD and SEM. The best results were obtained for the 1130 rpm rotation speed (ω) and 12 mm/min travel speed (v), with the UTS of 156 MPa (~70% of Cu strength). The microhardness test showed that TMAZ and base metal of Al side had the maximum hardness amounts (148 and 155 HV, respectively). Generally, increase in the ω²/v ratio caused the nugget zone and HAZ grain size to increase. The results revealed the formation of Al₂Cu and Al₄Cu₉ intermetallic compounds in the border zone of the joints. The fractography results showed the occurrence of cleavage fracture in all the samples.     

Linear friction welding of Ti-6Al-4V: Processing,microstructure, and mechanical-property inter-relationships

The linear friction welding behavior of Ti-6Al-4V was investigated using varying processing conditions of frequency (15 to 70 Hz), amplitude (1 to 3 mm), pressure (50 to 90 MPa), and axial shortening (1 to 2 mm). Examination of linear friction welded Ti-6Al-4V using microscopic techniques indicated that the process requires certain critical conditions at the interface and its adjacent region to be reached for producing joints without structural defects along the weld centerline, such as voids or oxide inclusions. Characterization of the weldments included analysis of the microstructural features of the weld and thermomechanically affected zones (TMAZs) in relation to the parent material. It was observed that in the weld region, exposure to supertransus temperatures (>995 °C) combined with hot-deformation working and rapid cooling after joining produced recrystallization of the beta grain structure that had a Widmanstätten alpha-beta transformation microstructure. In the TMAZ, the bimodal microstructure of the parent material was deformed and the presence of elongated alpha grains with broken beta-phase particles was established. Through examination of the mechanical properties, using microhardness and tensile testing, the integrity of the joints was determined in order to assess the impact of the various processing parameters and to define the optimum welding conditions.     

Effect of Arc Welding Processes on the Weld Attributes of Type 316LN Stainless Steel Weld joint

The present study aims at understanding the effect of various arc welding processes on the evolution of microstructure, mechanical properties, residual stresses and distortion in 9 mm thick type 316LN austenitic stainless steel weld joints. Weld joints of type 316LN stainless steel were fabricated by three different arc welding processes which were commonly employed in the nuclear industry. All the weld joints passed radiographic examination. Microstructural characterization was done using optical and scanning electron microscope. Volume fraction of δ-ferrite was lowest in the A-TIG weld joint. The A-TIG welded joint exhibited adequate strength and maximum impact toughness values in comparison to that of weld joints made by SMAW and FCAW processes. The A-TIG weld joint was found to exhibit lowest residual stresses and distortion compared to that of other welding processes. This was attributed to lower weld metal volume and hence reduced shrinkage in the A-TIG weld joint compared to that of weld joints made by FCAW and SMAW processes which involved v-groove with filler metal addition. Therefore, type 316LN stainless steel A-TIG weld joint consisting of lower δ-ferrite, adequate strength, high impact toughness, lower residual stresses and distortion was suited better for elevated temperature service compared to that of SMAW and FCAW weld joints.     

Effect of Laser Beam Welding on Microstructure and Mechanical Properties of Commercially Pure Titanium

Laser beam welding of commercially pure titanium sheets were carried out at different operating conditions. Laser powers of 2.0 and 2.5 kW, beam diameters of 0.18 and 0.36 mm and welding speeds of 4–8 m/min were used. The microstructure and mechanical properties of the welded samples were investigated in the present study. It was observed that the grain size of the welded samples increased with increasing laser power while it decreased with increasing welding speed and beam diameter. The sample welded at 2.5 kW laser power with 4 m/min welding speed and 0.36 mm beam diameter had comparable tensile properties with the base metal.     

Production of Wire From AA7277 Aluminum Chips via Friction-Stir Extrusion (FSE)

In this research, fully consolidated wires from aluminum alloy AA7277 machining chips were produced by the friction-stir extrusion (FSE) process. The components used in the friction-stir extrusion process consist of a stationary cartridge and a rotating plunger with a scroll-faced head. The rotating plunger was rotated at three different speeds. Optical microscopy was used to probe the microstructures formed in the wires. The hardness profile of each sample is characterized using a Vickers microhardness tester. In this work, surface quality is sufficient by using a rotation speed of 160 rpm. Cold crack and hot crack defects were shown on wires fabricated using either too low or too high plunger rotation speeds. The microstructure of extruded wire is composed of fully equiaxed, recrystallized fine grains in the center of samples. The microhardness tests show an uneven distribution, and the hardness of the center was lower than that of the parent metal. The tensile tests revealed that the mechanical properties of the extruded wires were comparable with parent material.     

Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel

 The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties.     

Effect of Heat Input on Macro,Micro and Tensile Properties of Flux Cored Arc Welded Ferritic Stainless Steel Joints

This paper discusses the influence of Flux Cored Arc Welding Process parameters such as welding current, travel speed, voltage on bead profile, metallurgical and mechanical properties of welds of 2 mm thick 409M ferritic stainless steel sheets. The study reveals that, grain coarsening, volume fraction of martensite, hardness of heat affected zone and % of delta ferrite in ER 309 weld metal increases with increase in heat input. However, the results show that variation of heat input does not make any significant effect on tensile strength of the joint. Hence, welding parameters that provide uniform bead profile for the weld are recommended for fabrication.     

Cold Metal Transfer Welding of Dissimilar A6061 Aluminium Alloy-AZ31B Magnesium Alloy: Effect of Heat Input on Microstructure,Residual Stress and Corrosion Behavior

Lap joints of aluminum alloy A6061-T6 and AZ31B magnesium alloy were produced by cold metal transfer welding with Al-5 %Si filler metal. Four heat inputs designated as A (175 J/mm), B (185 J/mm), C (195 J/mm) and D (205 J/mm) were used during the process and the joints made were subjected to analysis of microstructure, mechanical properties and corrosion behaviour. The thickness of the fusion line (diffusion layer) varied from 3 to 12 µm depending on the heat input. It was also found that the joints made using the heat input of 205 J/mm exhibited highest tensile strength of 360 N/mm, least tensile stress in the weld and better pitting corrosion resistance. Electron microscopy study of the weld revealed the presence of β′-Mg₂Si, Al₆Mn and β-Al₃Mg₂ particles. X-ray diffraction study in the weld revealed the formation of γ-Al₁₂Mg₁₇ and β-Al₃Mg₂ phase with Mg₂Si strengthening precipitates. Tensile failure occurred at the fusion line near magnesium.     

大厚度紫铜搅拌摩擦焊接

采用搅拌摩擦焊接方法对厚度为30mm和50mm的T2紫铜板分别进行单面和双面焊接实验,并对焊缝的微观组织与力学性能进行了分析.结果表明:在一定的参数范围内,可获得表面成形美观、内部无缺陷且变形小的对接接头.30mm T2紫铜板单道焊焊后平均抗拉强度为177.2MPa,达到母材的81.7%,断后平均伸长率为25.4%;焊缝横切面显微硬度分布波动较大,最低值位于前进侧热影响区底部,说明了此处位置是焊缝薄弱环节.     

1800 MPa热成形钢与CR340LA低合金高强钢激光焊接性能

采用光纤激光焊接设备对1800 MPa级热成形钢与CR340LA低合金高强钢进行对接激光拼焊,研究了不同激光焊接功率和焊接速度下焊接接头的组织演变规律及热冲压成形性能,并对焊接接头的力学性能和硬度进行了分析。结果表明,3种焊接工艺下激光拼焊原板综合力学性能相差较小,由焊接接头造成的伸长率和抗拉强度的损失均在母材的28.3%和9.1%以内。激光焊接后焊缝区均为粗大、高硬度的马氏体结构;两侧热影响区组织主要为铁素体和马氏体,接头未出现明显的软化区。激光拼焊原板拉伸试样均断裂于CR340LA母材区,距离焊缝12 mm左右,且存在焊缝隆起现象。选取焊接功率和焊接速率分别为4000 W和0.18 m·s?1的焊接试样在高温下进行热冲压成形检测,未出现焊缝开裂,热成形后拼焊板具有良好性能,满足汽车激光拼焊板使用要求,拉伸结果表明,试样断裂位置与未热冲压成形前一致,均位于CR340LA母材区,拉伸过程中,焊缝向高强度母材侧偏移,在弱强度母材侧产生应力集中并缩颈断裂。      

Establishing a Mathematical Model to Predict the Tensile Strength of Friction Stir Welded Pure Copper Joints

This investigation was undertaken to predict the tensile strength of friction stir welded pure copper. Response surface methodology based on a central composite rotatable design with four welding parameters, five levels, and 31 runs was used to conduct the experiments and to develop the mathematical regression model by means of Design-Expert software. Four welding parameters considered were tool profile design, rotational speed, welding speed, and axial force. Analysis of variance was applied to validate the predicted model. Confirmation experiments including microstructural characterization and conducted tensile tests showed that developed models are reasonably accurate. The results showed that the joints welded using the square and triangular tools had higher tensile strength compared to the joints welded using other tools. The increase in tool rotational speed, welding speed, and axial force resulted in increasing the tensile strength of the joints up to a maximum value. Also, the developed model showed that the optimum parameters to get a maximum of tensile strength were rotational speed, welding speed, and axial force of 942 rpm, 84 mm/min, and 1.62 kN, respectively.     

Metallurgical and Mechanical Characterization of Laser Spot Welded Low Carbon Steel Sheets

This paper aims at investigating metallurgical and mechanical characterization of low carbon steel laser spot welds. Microstructural examinations, microhardness tests and quasi‐static tensile‐shear tests were preformed. Mechanical properties of the welds were described in terms of peak load and failure mode. The effects of laser spot welding parameters including pulse frequency, laser energy, welding speed, pulse width and welded circle diameter, on low carbon steel laser spot weld performance were studied using the Taguchi design of experiment method. It was found that the effective laser pulse energy is the controlling factor in the determination of mechanical strength of laser spot welds.     

Microstructure and mechanical properties of Al-Mg-Mn-Zr-Er weld joints filled with Al-Mg-Mn-Zr and Al-Mg-Mn-Zr-Er weld wires

The Al-Mg-Mn-Zr-Er alloy sheets with a thickness of 4 mm were welded by TIG welding, the microstructures and mechanical properties of Al-Mg-Mn-Zr-Er alloy weld joints filled with F1.6 mm Al-Mg-Mn-Zr and Al-Mg-Mn-Zr-Er welding wires were studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, hardness testing and tensile mechanical properties testing. The result showed that, the tensile strength increased by 57 MPa and the coefficient of weld joint reached 0.8 when Al-Mg-Mn-Zr-Er welding wire was used as filling material. The tensile strength and elongation of weld joint filled with Al-Mg-Mn-Zr-Er welding wire were 19% and 85% higher those that of filled with Al-Mg-Mn-Zr welding wire respectively, which resulted from grain refinement strengthening and dispersion strengthening of Al₃Er.     

Effect of Process Parameters on Microstructure and Mechanical Properties in Friction Stir Welding of Aluminum Alloy

Friction stir welding process is a promising solid state joining process with the potential to join low melting point materials, particularly aluminum alloys. The most attractive reason for this is the avoidance of solidification defects formed during conventional fusion welding processes. Tool rotational speed and the welding speed play a major role in deciding the weld quality. In the present work an effort has been made to study the effect of the tool rotational speed and welding speed on mechanical and metallurgical properties of friction stir welded joints of aluminum alloy AA6082-T651. The micro hardness profiles obtained on welded zone indicate uniform distribution of grains in the stir zone. The maximum tensile strength obtained is 263 MPa which is about 85% of that of base metal. Scanning electron microscope was used to show the fractured surfaces of tensile tested specimens.     

Welding L415/316L Bimetal Composite Pipe Using Post-Internal-Welding Process

The butt welding of bimetal composite pipes generally adopts single-side welding, which easily gives rise to the problems such as high cost or crack initiation. In this paper, the butt welding of L415/316L bimetal mechanical lined pipes was conducted using post-internal-welding process, which is double-side welding process, proposed by the authors. Firstly, the effect of groove shape on the weld process was discussed. Then, microstructures and mechanical and corrosion-resistance properties of welded joints welded using two different welding materials, 309MoL and 309L, were investigated. The results show that the most suitable groove is that L415 is V shape with angle of 60° and blunt edge of 1 mm and 316L is stripped 6–8 mm. The weld of both 309MoL and 309L is composed of austenite and a small amount of ferrite, but the presence of Mo can refine the grains and increase the content of ferrite phase. The width of transition layer is about 0.6–0.8 mm located at the weld junction of stainless steel weld and carbon steel weld, and the transition layer mainly contains martensite. The tensile and bending performances of the welded joints using both 309MoL and 309L do meet the standard requirements. The welding wire 309MoL can improve the corrosion resistance to Cl− compared to 309L. It is advisable to use the post-internal-welding process and 309MoL for the welding of bimetal composite pipes under environments containing Cl−.     

Effect of Tool Shoulder Diameter to Plate Thickness Ratio on Mechanical Properties and Nugget Zone Characteristics During FSW of Dissimilar Mg Alloys

During friction stir welding (FSW), frictional heat is produced in the region between the tool shoulder and base materials due to the movement of the rotating tool along the line of joint. In this paper, an experimental investigation was made to understand the influence of the tool shoulder diameter (primary source of heat generation) on the microstructural characteristics and mechanical properties of dissimilar Mg alloys namely AZ80A and AZ91C. From the experimental results, it was observed that the use of FSW tool having 17.5 mm shoulder diameter (3.5 times the plate thickness) produced defect free sound joints with superior mechanical properties compared to its counterparts. Moreover, the uniformly distributed fine sized grains of nugget zone also contributed to the sound quality joints. From this investigation, it was understood that higher heat input is essential for enabling the required mixing of materials during FSW of dissimilar Mg alloys.