Feasibility of joining AZ31B magnesium metal matrix composite by friction welding

The present study investigates the feasibility of joining AZ31B magnesium nanocomposites by rotational friction welding. The AZ31B magnesium metal matrix composite, which was reinforced with alumina (Al₂O₃, average particle size of 50 nm) and calcium (Ca), was produced by a hybrid casting process and hot extruded at 350 °C. Joining processes were done by varying the friction welding parameters. The integrity of the joints was investigated by optical microscopy. The mechanical properties of the joints were examined by tension tests and micro hardness tests. The efficiencies of the joints were analysed using statistical analysis. The fracture mode was studied using a scanning electron microscope. It was observed that as the friction pressure and forging pressure increased, the joint efficiency increased. Also, as the friction time increased, the efficiency of the joint decreased.     

Mechanical properties of friction welded 6063 aluminum alloy and austenitic stainless steel

Friction welding of dissimilar metal combination of aluminum alloy and austenitic stainless steel was examined to investigate the effect of welding conditions on mechanical properties of the dissimilar metal combination. The welded joints were produced by varying forge pressure (F _g), friction pressure (F _r), and burn-off length (B). The joints were subjected to mechanical testing methods such as the tension, notch Charpy impact tests. The tensile strength and toughness decrease with an increase in friction pressure. The tensile strength decreases with an increase in burn-off length at a low forge pressure while tensile strength increases with an increase in burn-off length at a high forge pressure. The tensile failure of the welded joint occurred in aluminum alloy just away from interface in the thermo-mechanically affected zone indicates good joint strength at the condition of low friction pressure, high forge pressure, and high burn-off length. The maximum tensile strength was observed with low friction pressure and high forge pressure. The tensile strength of dissimilar joint is approximately equal to tensile strength of 6063 aluminum alloys at the condition of low friction pressure, high forge pressure, and high burn-off length. The tensile and impact failure of joints was examined under scanning electron microscope and failure modes were discussed.     

Evaluation of interfacial bonding in dissimilar materials of YSZ-alumina composites to 6061 aluminium alloy using friction welding

The interfacial microstructures characteristics of alumina ceramic body reinforced with yttria stabilized zirconia (YSZ) was evaluated after friction welding to 6061 aluminum alloy using optical and electron microscopy. Alumina rods containing 25 and 50 wt% yttria stabilized zirconia were fabricated by slip casting in plaster of Paris (POP) molds and subsequently sintered at 1600 °C. On the other hand, aluminum rods were machine down to the required dimension using a lathe machine. The diameter of the ceramic and the metal rods was 16 mm. Rotational speeds for the friction welding were varied between 900 and 1800 rpm. The friction pressure was maintained at 7 MPa for a friction time of 30 s. Optical and scanning electron microscopy was used to analyze the microstructure of the resultant joints, particularly at the interface. The joints were also examined with EDX line (energy dispersive X-ray) in order to determine the phases formed during the welding. The mechanical properties of the friction welded YSZ-Al₂O₃ composite to 6061 alloy were determined with a four-point bend test and Vickers microhardness. The experimental results showed the degree of deformation varied significantly for the 6061 Al alloy than the ceramic composite part. The mechanical strength of friction-welded ceramic composite/6061 Al alloy components were obviously affected by joining rotational speed selected which decreases in strength with increasing rotational speed.     

Prediction and optimization of friction welding parameters for super duplex stainless steel (UNS S32760) joints

Friction welding finds widespread industrial use as a mass production process for joining materials. Friction welding process allows welding of several materials that are extremely difficult to fusion weld. Friction welding process parameters play a significant role in making good quality joints. To produce a good quality joint it is important to set up proper welding process parameters. This can be done by employing optimization techniques. This paper presents a multi objective optimization method for optimizing the process parameters during friction welding process. The proposed method combines the response surface methodology (RSM) with an intelligent optimization algorithm, i.e. genetic algorithm (GA). Corrosion resistance and impact strength of friction welded super duplex stainless steel (SDSS) (UNS S32760) joints were investigated considering three process parameters: friction force (F), upset force (U) and burn off length (B). Mathematical models were developed and the responses were adequately predicted. Direct and interaction effects of process parameters on responses were studied by plotting graphs. Burn off length has high significance on corrosion current followed by upset force and friction force. In the case of impact strength, friction force has high significance followed by upset force and burn off length. Multi objective optimization for maximizing the impact strength and minimizing the corrosion current (maximizing corrosion resistance) was carried out using GA with the RSM model. The optimization procedure resulted in the creation of nondominated optimal points which can aid the process operator to fix the input control variables. The selection of a point from the Pareto front will always be a trade-off between the corrosion resistance and impact strength of the weld depending on the application.     

Optimization for friction welding parameters with multiple performance characteristics

Friction Welding is a variation of pressure welding method. Though some experience has already been accumulated in the industrial application of friction welding, achieving the optimal processing parameters is still a difficult task. This work is putting a step forward to achieve the best possible design. This paper presents an investigation on the optimization and the effect of welding parameters on multiple performance characteristics (tensile strength and the metal loss) obtained by friction welded joints. A plan of experiments based on the Taguchi method was designed. The output variables were the tensile strength and metal loss of the weld. These output variables were determined according to the input variables, which are the Heating Pressure (HP), Heating Time (HT), Upsetting Pressure (UP) and Upsetting Time (UT). The main objectives of this study are maximization of tensile strength and minimization of metal loss. By statistical analysis, an optimal level of combination of processing parameters is achieved. To validate the optimization, experience were conducted at optimum parameters.     

A study on mechanical and microstructure characteristics of the STS304L butt joints using hybrid CO2 laser-gas metal arc welding

In order to examine mechanical characteristics of the stainless steel (STS304L) hybrid welded butt joints, two-dimensional thermal elasto-plastic analysis has been carried out. To this end, a 2D simulation model has been developed considering hybrid welding features. Based on thermal history data obtained from this heat source model, the residual stress distribution in weld metal (WM), heat affected zone (HAZ) and base metal (BM) characteristics have been calculated and found to be in reasonable agreement with the experimentally measured values. In order to investigate the effect of welding process, thermal elasto-plastic behaviour of the hybrid welded joints was compared with a welded joints obtained by conventional submerged arc welding (SAW) process. The results show that the longitudinal residual stress in the hybrid welded joints is less (13–15%) than that of the SA welded joints. Weld metal formed in both welding processes shows very fine dendritic structure. Due to higher heat input in SAW, the HAZ size of the SA welded joints is more than twice that of the hybrid welded joints. Therefore, from mechanical and metallurgical point of view, it could be confirmed that it makes a good sense to use SAW instead of hybrid CO₂ laser-gas metal arc welding (GMAW) for butt joint of the STS304L thick steel.     

铝 / 镁异种金属搅拌摩擦焊研究现状及发展趋势

为进一步优化焊接工艺,提高铝/镁异种金属搅拌摩擦焊接头的性能,促进铝/镁异种金属结构在航空航天、轨道交通、汽车工业等领域的广泛应用,综述了近5年来国内外铝/镁异种金属搅拌摩擦焊接的最新研究成果,对焊接工艺参数、接头的力学性能、微观组织以及异种金属搅拌摩擦焊的新工艺进行了总结和分析。国内外大量研究结果表明,通过选择合适的工艺参数、改变搅拌针的偏移,可以获得抗拉强度较高、焊缝成形良好的铝/镁异种金属搅拌摩擦焊接头,焊缝中存在的金属间化合物是导致焊接接头性能不能满足工程应用的主要因素,但目前对于搅拌摩擦焊接过程中金属间化合物的产生、分布规律缺乏深入研究。     

不同摩擦压力下TB2线性摩擦焊过程参量的变化规律研究

目的 深入分析钛合金线性摩擦焊接过程,掌握焊接参数变化时各摩擦阶段过程参量的变化规律及其与接头质量的关系。方法 采用不同摩擦压力进行TB2钛合金线性摩擦焊接试验,基于信号采集获得了焊接过程典型参量的变化曲线。结果 曲线特征分析表明,摩擦压力40 MPa时,在设定时间内未达到稳定摩擦阶段,曲线特征异常,接头明显未焊合。随摩擦压力增大至70和100 MPa,各曲线变化规律与线性摩擦焊接4个典型阶段相吻合,分别得到焊缝宽度不同的无缺陷接头。70 MPa下摩擦剪力过渡平缓,界面塑性金属的产生与挤出较为协调,焊接过程的稳定性及接头质量易于得到控制。结论 通过对比不同参数下焊接过程参量的变化规律,有助于认识不同线性摩擦焊接过程的内在差异,从而判断接头质量并选取合适的焊接参数。     

2219铝合金搅拌摩擦焊接头组织和性能的不均匀性研究

目的 针对2219铝合金搅拌摩擦焊接头受焊接热作用和机械搅拌作用的影响,极易产生组织和力学性能不均匀的情况,深入研究接头的局部力学性能,为焊接工艺优化提供理论指导.方法 采用显微组织分析与数字图像相关(DIC)技术测试相结合的方法,对2219铝合金搅拌摩擦焊接头的组织和局部力学性能进行表征,并建立搅拌摩擦焊接头各区域的局部力学性能模型.结果 2219铝合金搅拌摩擦焊接头的力学性能薄弱区为热机影响区.试样断裂前该区域局部应力达到345 MPa,局部应变为18.9％,而此时母材应变仅为1.91％.结论 热机影响区的组织在焊接热作用和机械搅拌的双重作用下发生了粗化和软化,导致该区的力学性能降低,是整个焊接接头的薄弱区域.     

Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al‐Mg‐Cu alloy

The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid‐state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024‐T3 Al‐Mg‐Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints.     

Double global optimum genetic algorithm–particle swarm optimization-based welding robot path planning

Spot-welding robots have a wide range of applications in manufacturing industries. There are usually many weld joints in a welding task, and a reasonable welding path to traverse these weld joints has a significant impact on welding efficiency. Traditional manual path planning techniques can handle a few weld joints effectively, but when the number of weld joints is large, it is difficult to obtain the optimal path. The traditional manual path planning method is also time consuming and inefficient, and cannot guarantee optimality. Double global optimum genetic algorithm–particle swarm optimization (GA-PSO) based on the GA and PSO algorithms is proposed to solve the welding robot path planning problem, where the shortest collision-free paths are used as the criteria to optimize the welding path. Besides algorithm effectiveness analysis and verification, the simulation results indicate that the algorithm has strong searching ability and practicality, and is suitable for welding robot path planning.     

Mechanical properties of friction stir butt‐welded Al‐5086 H32 plate

Al‐5086 H32 plates with a thickness of 3 mm were friction stir butt‐welded using different welding speeds at a tool rotational speed of 1600 rpm. The effect of welding speed on the weld performance of the joints was investigated by conducting optical microscopy, microhardness measurements and mechanical tests (i.e. tensile and bend tests). The effect of heat input during friction stir welding on the microstructure, and thus mechanical properties, of cold‐rolled Al‐ 5086 plates was also determined. The experimental results indicated that the maximum tensile strength of the joints, which is about 75 % that of the base plate, was obtained with a traverse speed of 200 mm/min at the tool rotational speed used, e.g. 1600 rpm, and the maximum bending angle of the joints can reach 180^o. The maximum ductility performance of the joints was, on the other hand, relatively low, e.g. about 20 %. These results are not unexpected due to the loss of the cold‐work strengthening in the weld region as a result of the heat input during welding, and thus the confined plasticity within the stirred zone owing to strength undermatching. Higher joint performances can also be achieved by increasing the penetration depth of the stirring probe in butt‐friction stir welding of Al‐5086 H32 plates.     

Experimental study of mechanical properties of friction welded AISI 1021 steels

Friction welding is widely used as a mass production method in various industries. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties.     

Experimental characterization of Ti6Al4V T joints welded through linear friction welding technique: microstructure and NDE

Linear friction welding (LFW) is an innovative solid-state welding technique that allows to manufacture joints with high mechanical properties. This technology has various applications in the aerospace field; in particular it is used to weld massive structural components made of Ti6Al4V. This paper deals with the experimental study of Ti6Al4V T-joints welded through LFW, with particular focus on the effectiveness of ultrasonic control in detecting and distinguishing welding defects within the joints. Aiming to this scope, joints with different properties were manufactured and tested:some were free from defects but with different metallurgy, and some had different types of defects. The results obtained proved that the ultrasonic control was an effective method to detect and identify defects in linear friction welded titanium joints, moreover it was possible to get information regarding the microstructure and in particular the extension of the different metallurgical zones induced by the welding process.     

Process optimization in the self-reacting friction stir welding of aluminum 6061-T6

Self-reacting friction stir welding (SR-FSW), also called bobbin-tool friction stir welding (BT-FSW), is a solid state welding process similar to friction stir welding (FSW) except that the tool has two opposing shoulders instead of the shoulder and a backing plate found in FSW. The tool configuration results in greater heat input and a symmetrical weld macrostructure. A significant amount of information has been published in the literature concerning traditional FSW while little has been published about SR-FSW. An optimization experiment was performed using a factorial design to evaluate the effect of process parameters on the weld temperature, surface and internal quality, and mechanical properties of self-reacting friction stir welded aluminum alloy 6061-T6 butt joints. The parameters evaluated were tool rotational speed, traverse speed, and tool plunge force. A correlation between weld temperature, defect formation (specifically galling and void formation), and mechanical properties was found. Optimum parameters were determined for the welding of 8-mm-thick 6061-T6 plate.     

Mechanical properties of friction stir butt welds of high nitrogen-containing austenitic stainless steel

In this study, the friction stir butt welding of 2-mm-thick high nitrogen-containing stainless steel (HNS; Ni-free austenitic stainless steel containing 1 mass% nitrogen) plates was performed using a load-controlled friction stir welding (FSW) machine with a Si₃N₄-based tool at various welding speeds, i.e., 50 mm/min, 100 mm/min, 200 mm/min and 300 mm/min, and a constant tool rotating speed of 400 rpm. To determine the optimum welding conditions to create reliable HNS FSW joints, the effect of the heat input on the mechanical properties of the HNS FSW joints was studied. The mechanical properties were evaluated by the Vickers hardness test and the tensile strength test. Full-penetrated and defect-free butt welded joints were successfully produced, under all the applied welding conditions. The stir zones consisted of very fine grained structures and showed an increase in the Vickers hardness. These joints also showed a higher tensile strength and yield strength than the base metal. In particular, the FSW welds obtained at a welding speed of 100 mm/min, which showed the best mechanical properties, had a relatively higher Vickers hardness, which indicates a good relationship between the welding parameter (heat input) and the hardness profile due to the microstructure refinements. It was estimated that these welding conditions were optimal, and under these conditions both grain growth and α-phase formation were prevented.     

Influence of friction stir welding process and tool parameters on strength properties of AA7075-T6 aluminium alloy joints

The aircraft aluminium alloys generally present low weldability by traditional fusion welding process. The development of the friction stir welding has provided an alternative improved way of satisfactorily producing aluminium joints, in a faster and reliable manner. In this present work, the influence of process and tool parameters on tensile strength properties of AA7075-T₆ joints produced by friction stir welding was analysed. Square butt joints were fabricated by varying process parameters and tool parameters. Strength properties of the joints were evaluated and correlated with the microstructure, microhardness of weld nugget. From this investigation it is found that the joint fabricated at a tool rotational speed of 1400 rpm, welding speed of 60 mm/min, axial force of 8 kN, using the tool with 15 mm shoulder diameter, 5 mm pin diameter, 45 HRc tool hardness yielded higher strength properties compared to other joints.     

铝合金薄板搭接高速 FSW 缺陷及断裂行为

目的 为了拓展搅拌摩擦焊技术应用,对薄板搭接结构高速搅拌摩擦焊工艺优化与工程应用提供 借鉴与指导。方法 采用圆锥无螺纹搅拌针,进行了 6061 铝合金薄板搭接高速搅拌摩擦焊接,对接头界 面缺陷及其断裂模式进行分析,探讨了转速对 6061 铝合金薄板搭接接头成形及性能的影响规律。结果 发现在无螺纹圆锥搅拌针、高转速（6000~9000 r/min）条件下,接头塑性金属在后退侧易形成飞边流出, 导致下板前进侧出现孔洞缺陷,且随转速增大,界面缺陷尺寸逐渐增大,当转速达到 10 000 r/min 时, 孔洞尺寸有所减小,此时接头拉剪强度最高,为 123 MPa。对试样拉剪断裂位置分析发现,高速搭接接 头断裂位置主要有两种,分别断裂在结合界面处或在前进侧下板,且转速在 9000 r/min 以上越趋向于在 结合界面断裂。结论 高转速搭接焊接必须协调轴肩相貌、焊接工装约束等条件,保证接头塑性金属充 分流动而不流失,才能获得成形良好无缺陷的接头。     

Effect of friction welding parameters on mechanical and metallurgical properties of aluminium alloy 5052–A36 steel joint

Abstract

The mechanical and metallurgical properties of friction welded joints between type 5052 aluminium alloy and type A36 steel have been studied in the present work. Joint strength increased with increasing upset pressure and friction time until it reached a crictical value. The strength of the joint settled at a lower value, compared with that of the base metal, in the case of increasing friction time, caused by the formation of an intermediate phase (intermetallic compound, oxides). The microstructure of 5052 alloy was greatly deformed near the weld interface, and underwent dynamic recrystallisation owing to frictional heat and deformation resulting from the friction welding process. Therefore, a very fine and equiaxed grain structure was observed near the interface. Elongated grains were observed outside the dynamic recrystallisation region at the peripheral part, while the A36 steel side was not deformed. The hardness of the near interface was slightly softer than that of the 5052 alloy base metal, and maximum softened width was ~8 mm from the interface. In the present work, the conditions of friction time t ₁ = 0.5 s and upset pressure P ₂ = 137.5 MPa gave maximum joint strength of 202 MPa when the friction pressure, upset time and rotation speed were fixed at 70 MPa, 5 s and 2000 rev min^-1, respectively, and these were the optimum friction welding conditions for the aluminium alloy 5052-A36 steel joint.     

Microstructure and mechanical properties of alumina-6061 aluminum alloy joined by friction welding

The study of the interface of ceramic/metal alloy friction welded components is essential for understanding of the quality of bonding between two dissimilar materials. In the present study, optical and electron microscopy as well as four-point bending strength and microhardness measurements were used to evaluate the quality of bonding of alumina and 6061 aluminum alloy joints produced by friction welding. The joints were also examined with EDX (energy dispersive X-ray) in order to determine the phases formed during welding. The bonded alumina-6061 aluminum samples were produced by varying the rotational speed but keeping constant the friction pressure and friction time. The experimental results showed that the effect of rotation speed and degree of deformation appears to be high on the 6061 Al alloy than on the alumina part. It is discovered that the weld interface formed included three different regions: unaffected zone (UZ), deformed zone (DZ), as well as transformed and recrystallized fully deformed zone (FPDZ). Therefore, when rotational speed increases, the thickness of full plastic deformed zone (FPDZ) at the interface increases as a result of more mass discarded from the welding interface. It was also observed that rotational speed of 2500 rpm can produce a very good joint and microhardness with good microstructure as compared to the other experimental rotational speeds.