Comparison of 2A12 aluminium alloy joint by ultrasonic assisted friction stir welding and friction stir welding

Ultrasonic assisted friction stir welding （UAFSW） is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, 2A12 aluminum alloy was welded by this process and conventional, respectively. The tensile tests, microstructure and fracture surface of FSW joint and UAFSW joint were analyzed. The research results show that the surface forming texture of ultrasonic assisted friction stir welding joint, compared with conventional, is finer and more uniform, showing metallic matte color. The grains are much finer in weld nugget zone, thermo-mechanically affected zone and heat-affected zone; S-phase particles size is much smaller and distribution is more homogeneous in the matrix. The tensile strength of UAFSW joint is 94. 13% of base metal, and the elongation is 11.77%. The tensile strength of FSW joint is 83.15% of base metal, and the elongation is 8.81%. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints.     

Effect of rotary direction and speed on mechanical properties in friction stir spot welding of A6061 sheets e

Friction stir spot welding of A6061 sheets was conducted using a tool with thread pin. The hook geometries, hook formation and mechanical properties of the joints welded with different rotary directions and speeds were investigated. The results show that the hook in the joint welded in clockwise was curved upwards and that in anticlockwise was curved downwards. The hook formation was related to the plastic material flow in the joint. With increasing the rotary speed in clockwise direction, the hook moved upwards and far way from the center of the keyhole, resulting in an increase in the effective weld width and a decrease in the effective sheet thickness. Three types of fractuces were observed and they were affected by the hook geometries. The tensile shear load increased firstly and then decreased when the rotary speed increased in clockwise direction, which was related to the hook geometries.     

Exploring material flow in friction stir welding using stacked structure of 2024 and 6061 aluminum alloys

An experimental technique based on stacked structures was developed to observe the material flow behavior of the friction stir welding （FSW） process. Analysis of section views along different directions revealed important new details of the material flow in FSW process. In this work, a general flow model of FSW was constructed based on the analysis of different static section views of stacked structure weld. The formation of onion rings was found to be a geometric effect due to layered deposition attd the extrusion occurred at the interface between flow arm （FA） and stirring zone （SZ）.     

Effect of ultrasonic vibration on the friction stir weld quality of aluminium alloy

A novel variant of friction stir welding process, referred as ultrasonic vibration enhanced friction stir welding, is developed to transmit ultrasonic vibration energy directly into the localized area of the workpiece near and ahead of the rotating tool. Experiments are conducted on 6061-T4 aluminium alloy plates by this new process and the conventional friction stir welding process, respectively. The morphology and macrograph of the welds under both conditions are observed and contrasted. The experimental results show that ultrasonic vibration enhanced friction stir welding can improve the weld formation quality and increase the welding efficiency. And it just needs a smaller axial downward force. Because that the added action of ultrasonic vibration energy may enhance the localized softening extent and the plastic flow around the tool. In addition, it also improves the mechanical properties of the welded joints.     

Numerical analysis of reverse dual-rotation friction stir welding process

A three-dimensional model of reverse dual-rotation friction stir welding （RDR-FSW） is developed to conduct the numerical simulation of heat generation and material flow during the process. The reverse rotation of the assisted shoulder and the tool pin is considered to model the heat generation rate. The predicted temperature difference between the advancing side and the retreating side in RDR-FSW is less than that in conventional FSW. There are two reverse flows during the RDR-FSW which is beneficial to the uniformity of the temperature profile. Due to the reverse rotation effects of the assisted shoulder, the predicted shape and size of thermal-mechanically affected zone （TMAZ） based on the iso-viscosity line are decreased greatly compared to the conventional FSW. It lays solid foundation for optimizing the process parameters in RDR-FSW.     

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

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 as σ_0.2 = 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, microstructure, and mechanical properties.     

Friction Stir Welding of Discontinuously Reinforced Aluminum Matrix Composites:A Review

Friction stir welding(FSW) is considered a promising welding technique for joining the aluminum matrix composites(AMCs) to avoid the drawbacks of the fusion welding. High joint efficiencies of 60%–100% could be obtained in the FSW joints of AMCs. However, due to the existence of hard reinforcing particles in the AMCs, the wearing of welding tool during FSW is an unavoidable problem. Moreover, the low ductility of the AMCs limits the welding process window. As the hard materials such as Ferro-Titanit alloy, cermet, and WC/Co were applied to produce the welding tools,the wearing of the tools was significantly reduced and the sound joints could be achieved at high welding speed for the AMCs with low reinforcement volume fraction. In this article, current state of understanding and development of welding tool wearing and FSW parameters of AMCs are viewed. Furthermore, the factors affecting the microstructure and mechanical properties of the joints are evaluated in detail.     

慢速搅拌摩擦加工对工业纯钛摩擦磨损性能的影响

目的利用慢速搅拌摩擦加工,获得工业纯钛细晶组织,提高其耐磨性能。方法采用慢速搅拌摩擦加工对TA2工业纯钛退火板材进行表面处理,获得细晶结构。使用EBSD技术和显微硬度检测仪对表面微观结构及力学性能进行表征。采用球盘式摩擦磨损试验仪对搅拌摩擦加工前后的样品进行摩擦磨损性能测试,计算磨损率,并使用SEM及EDS分析磨痕特征。结果搅拌摩擦加工处理后,工业纯钛晶粒尺寸显著细化,小角度晶界比例较高,加工硬化程度高。搅拌摩擦加工样品氧化磨损较为严重,粘着磨损程度减小。搅拌摩擦加工后,样品主要磨损方式由粘着磨损和二体磨损转变为氧化磨损和三体磨损。经过180 r/min、25 mm/min处理的工业纯钛磨损率仅为未加工样品的1/4左右。结论慢速搅拌摩擦加工可同时提高工业纯钛表面硬度及耐磨损性能,较小的晶粒尺寸及合适的加工硬化程度可减轻粘着磨损和磨粒磨损。     

AZ31镁合金搅拌摩擦点焊

研究了搅拌头旋转频率以及停留时间对AZ31镁合金搅拌摩擦点焊接头力学性能的影响.随着旋转频率的增大,不同搅拌针条件下,AZ31搅拌摩擦点焊接头的力学性能均呈现先增大后减小的趋势.随着停留时间的延长,AZ31搅拌摩擦点焊接头的力学性能先增大随后在一定范围内波动.结果表明,结合宽度是影响搅拌摩擦点焊接头力学性能的重要因素,...     

Investigation of microstructure and mechanical properties of friction stir lap jointed Monel 400 and Inconel 600

This study was conducted to investigate the microstructure and mechanical properties of friction stir lap joints. Monel 400 and Inconel 600 were selected as the experimental materials, and friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. The application of friction stir welding to Monel 400 effectively reduced the grain size in the stir zone; the average grain size of Monel 400 was reduced from 11.9 μm in the base material to 4.2 μm in the stir zone, which resulted in an improvement in the mechanical properties of the stir zone. The joint interface between Monel 400 and Inconel 600 showed a relatively sound weld without grooves or cracks, and only a small amount of voids with a size of 0.5 μm; however, no intermetallic compounds were observed in the lap jointed interface. Moreover, the hook on the advancing side of Monel 400 was formed from Inconel 600, which contributed to maintenance of the tensile strength. The evolution of microstructures and mechanical properties of friction stir lap jointed Monel 400 and Inconel 600 are also discussed herein.     

Effect of temperature field on flashes formation of continuous drive friction welding

On basis of the finite element software DEFORM, the 2D coupled thermo-mechanical model of continuous drive friction welding of ring parts is established. The temperature and the flashes during the welding process are investigated. The results of numerical simulation show that the temperature of friction surface is higher than that of other region and the peak temperature increases with the increase of welding time. During the process of friction stage, no flash appears because of the low temperature and the small axial friction pressure. At the forging stage, the flashes appear, whose dimensions and bending degree increase with the increase of welding temperature. Moreover, with the increase of rotational velocity and axial forging pressure, the dimensions and the bending degree of flashes of continuous drive friction welding increase.     

搅拌摩擦焊接缺陷的补焊方法

搅拌摩擦焊接方法在某些条件下也会造成焊接缺陷的产生,其中对接头性能有显著影响的缺陷包括沟槽、孔洞和未焊合.针对这三种类型的缺陷,用搅拌摩擦焊接方法进行补焊,以此研究补焊接头的焊缝成形和力学性能.结果表明,采用搅拌摩擦补焊方法能够消除沟槽、孔洞和未焊合等搅拌摩擦焊接缺陷;在优化的补焊工艺参数下,能够获得焊缝成形良好的补焊接头,其性能与优质原始接头的性能相当;补焊接头在拉伸测试中均在焊缝的后退侧发生断裂,拉伸断口具有明显的韧窝特征.     

Finite element analysis of the effect of micro-pore defect on linear friction welding of medium carbon steel

Micro-pore is a very common material defect. In the present paper, the temperature fields of medium carbon steel joints with and without micro-pore defect during linear friction welding （LFW） were investigated by using finite element method. The effect of micro-pore defect on the axial shortening of joints during LFW was examined. The x- and y-direction displacements of micro-pore during the LFW process were also studied. In addition, the shape of micro-pore after LFW was observed. The heat conducted from the weld inteace to the specimen interior. The fluctuation range of the temperature curves for the joint with micro-pore is larger than that without micro-pore. Position of micro-pore changes with the change of the friction time. The circular shape of micro-pore becomes oval after welding.     

铝合金无减薄搅拌摩擦焊工艺优化及特征分析

为提高无减薄搅拌摩擦焊接头力学性能,基于响应面法对参数进行优化,建立了响应面模型,并对模型进行回归分析. 结果表明,无减薄搅拌摩擦焊是成形优良的焊接工艺,而且焊接参数对接头拉伸性能影响明显,其中主轴转速及焊接速度对其影响更为显著. 在无缺陷条件下,提高主轴转速的同时选取适中的焊接速度,以得到性能更优的焊接接头. 焊接参数为主轴转速1 000 r/min,焊接速度200 mm/min、轴肩下压量0.25 mm时,接头的抗拉强度最大为363 MPa,为母材的94.3%,断后伸长率11.2%. 而且相比于常规搅拌摩擦焊,无减薄搅拌摩擦焊在厚度方向上的性能更加均匀.     

T2纯铜大载荷超低速搅拌摩擦焊接头强韧化机理

采用大载荷超低速搅拌摩擦焊工艺对2 mm厚的T2纯铜进行焊接,利用光学显微镜、扫描/透射电子显微镜、电子背散射衍射、硬度测试以及静拉伸试验对焊接接头的微观组织和力学性能进行研究. 结果表明,焊接热循环得到显著改善,有效抑制了由焊后余热带来的退火软化作用,彻底消除热影响区. 搅拌区由含有大量孪晶组织的超细晶构成,搅拌区抗拉强度和断后伸长率分别较母材提高了94%和69%. 文中提供了一种简单有效的方法,可同时提高纯铜搅拌摩擦焊搅拌区的强度和韧性.     

搅拌摩擦成型对铝基复合材料性能影响

采用搅拌摩擦成型技术对铸造SiC颗粒增强铝基复合材料进行改性，从组织、力学性能和摩擦磨损性能方面进行对比分析。结果表明:搅拌摩擦成型技术能修复缺陷组织、细化晶粒，搅拌时的剪切力使得SiC颗粒被打碎并分散均匀，提高材料的力学性能，抗拉强度和屈服强度分别提高14%和16%；搅拌摩擦成型修复后材料摩擦系数的稳定性得到显著提高。     

热源同轴辅助搅拌摩擦焊工艺特性分析

研究了激光同轴辅助搅拌摩擦焊中激光/搅拌摩擦焊的热量分配对不同系列铝合金焊缝成形、接头力学性能及显微组织的影响,并得到了相应的优化能量分配条件.结果表明,加入激光辅助热源可有效扩大工艺参数窗口,特别是流动性差的5A06和2219铝合金,焊接速度可提升30%以上.激光辅助热源对6061及5A06铝合金焊接接头性能影响较小,对2219铝合金搅拌摩擦焊接头的性能影响明显,焊接热输入增大后,接头性能下降,但总得来说,加入激光辅助热源能够在更小的焊接热输入下获得更高的接头性能.     

异种铝合金摩擦焊接移动速度和旋转速度的优化(英文)

在摩擦焊接过程中的热效应导致的高模量使铝合金容易变形、强度降低。对船用异种铝合金进行了搅拌摩擦焊接。确定5052-0和6061-T6铝合金在焊接时移动速度和旋转速度的最优条件。得到铝合金最佳焊接条件为移动速度61mm/min和旋转速度1600r/min。     

铝/铜异种材料搅拌摩擦焊接工艺的优化

搅拌摩擦焊(FSW)是近几年发展较快的新型摩擦焊接技术.国内外研究较多的是铝合金及异种铝合金的搅拌摩擦焊接,但对铝/铜异种搅拌摩擦焊接的研究尚不多见.在此通过大量试验,分别在900-1500 rpm、20-50mm/min范围内调整搅拌旋转速度和焊接速度,优化焊缝的成形质量.结果表明,优化工艺参数可以实现铝/铜异种金属...     

搅拌摩擦加工制备纳米RE/Al2O3增强铝基复合材料

铝基复合材料因其优异的物理性能及机械性能已得到广泛应用.文中通过在2219-O铝合金内部添加不同比例的RE/Al₂O₃纳米粉末,利用搅拌摩擦加工技术,制备铝基复合材料.并对搅拌区进行金相、拉伸、硬度、SEM,EDS和XRD等试验.结果表明,搅拌区金属在搅拌头强烈的搅拌摩擦作用下发生显著的塑性变形和连续动态再结晶,形成细小的等轴晶粒,并具有明显的洋葱环组织.复合材料的抗拉强度为母材的163%、屈服强度为母材的195%,同时硬度也明显增加.但是不同稀土比例对金属基复合材料的组织形貌和力学性能影响不大.大块复合材料制备过程粉末添加及隧道型缺陷的控制是关键.