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1.
Comparison of 2A12 aluminium alloy joint by ultrasonic assisted friction stir welding and friction stir welding
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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. 相似文献
2.
Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding 总被引:1,自引:0,他引:1
Ultrasonic vibration enhanced friction stir welding (UVeFSW) is a recent modification of conventional friction stir welding (FSW), which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy (2024-T4) was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases. 相似文献
3.
《Science & Technology of Welding & Joining》2013,18(1):81-86
AbstractThe influence of tool design on the energy output, microstructural features and overlap shear strength properties of friction stir spot welds made of AZ31 base material is examined. The mechanical properties of AZ31 friction stir spot welds made using three-flat/threaded tools are superior to those in joints made using a tool with a threaded pin at all tool rotational speed settings. It is proposed that the failure load properties are optimised when the friction stir spot welding operation is carried out in such a manner that it produces a large bonded width, a small v/t ratio (the height of the hook region above the sheet intersection divided by the thickness of the upper sheet) and a hook region, which is curved outwards from the tool axis. 相似文献
4.
Exploring material flow in friction stir welding using stacked structure of 2024 and 6061 aluminum alloys
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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). 相似文献
5.
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. 相似文献
6.
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. 相似文献
7.
对6061-T6铝合金点焊接头进行单点疲劳试验,确定6061-T6铝合金回填式搅拌摩擦点焊的疲劳断裂原因,得出6061-T6铝合金的S-N曲线以及条件疲劳极限.通过对载荷水平为1.5 kN的6061-T6 RFSSW疲劳试样进行金相分析以及断口扫描分析,得到了6061-T6铝合金疲劳断裂原因以及疲劳断口特征.结果表明,6061-T6点焊接头中的钩状缺陷和上下板结合处缺口尖端的应力集中是造成疲劳破坏的主要原因,疲劳裂纹始于上下板搭接处焊点的钩状缺陷外边缘,即缺口尖端处;在焊接过程中,应通过优化工艺参数尽量减小钩状缺陷的尺寸以及降低缺口处的应力集中,从而提高焊点的疲劳寿命. 相似文献
8.
H. Badarinarayan Q. Yang S. Zhu 《International Journal of Machine Tools and Manufacture》2009,49(2):142-148
Friction stir spot welding is performed on 5083 Al alloy using tools with a conventional cylindrical pin and the proposed triangular pin. Partial metallurgical bond (called as ‘hook’) is formed in the weld region between the overlapped metal sheets. The tool-pin geometry significantly affects the hook shape. Under the same process condition, welds made with the cylindrical pin have a continuous hook which bypasses the stir zone and points downward towards the weld bottom. By contrast, for welds made with the triangular pin, the hook is directed upwards and then arrested at the periphery of the stir zone. The difference in the hook shape could be attributed to the asymmetric rotation of the triangular pin that may cause the material in the vicinity of the pin to move back and forth in the radial direction resulting in the hook being broken-up (dispersed) in the stir zone. In addition, the triangular pin results in a finer grain structure in the stir zone compared to the cylindrical pin. Static strength of welds made with the triangular pin is twice that of welds made with the cylindrical pin, which is attributed to the finer grain size as well as tensile failure mode as a result of the arrested hook. 相似文献
9.
Friction Stir Welding of Discontinuously Reinforced Aluminum Matrix Composites:A Review 总被引:1,自引:0,他引:1
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. 相似文献
10.
H. Badarinarayan Y. Shi X. Li K. Okamoto 《International Journal of Machine Tools and Manufacture》2009,49(11):814-823
Friction stir spot welding is performed on 5754 Al alloy to investigate the effect of tool geometry on hook formation. Partial metallurgical bond (called as ‘hook’) is formed in the weld region between the overlapped metal sheets. The tool geometry is found to significantly affect the hook formation. First, welds are made to compare the effect of three shoulder profiles: concave, convex and flat (all having threaded cylindrical pins) on the hook geometry and static strength. The inherent concave profile resulted in a higher effective top sheet thickness that produced the highest weld strength. Next, with the concave shoulder profile selected, the effects of two different pin profiles: cylindrical and triangular are evaluated. Under the same process condition, welds made with the cylindrical pin have a continuous hook which bypasses the stir zone and terminates close to the keyhole. By contrast, for welds made with the triangular pin, the hook is directed upwards and then arrested at the periphery of the stir zone. The difference in the hook shape can be attributed to the material flow. Prior study shows that the static strength of welds made with the triangular pin is twice that of welds made with the cylindrical pin. 相似文献
11.
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,... 相似文献
12.
An error back propagation (BP) neural network prediction model was established for the shunt current compensation in series resistance spot welding. The input variables for the neural network consist of the resistivity of the material, the thickness of workpiece and the spot spacing, and the shunt rate is outputted. A simplified calculation for the shunt rate was presented based on the feature of the constant-current resistance spot welding and the variation of the resistance in resistance spot welding process, and then the data generated by simplified calculation were used to train and adjust the neural network model. The neural network model proposed was used to predict the shunt rate in the spot welding of 20# mlid steel (in Chinese classification) (in 2. 0 mm thickness) and 10# mild steel (in 1.5 mm and 1.0 mm thickness). The maximum relative prediction errors are, respectively, 2. 83%, 1.77% and 3.67%. Shunt current compensation experiments were peoCormed based on the neural network prediction model proposed to check the diameter difference of nuggets. Experimental results show that maximum nugget diameter deviation is less than 4% for both 10# and 20# mlid steels with spot spacing of 30 mm and 50 mm. 相似文献
13.
Cockcrofi-Latham fracture criterion was applied to predict the fracture of high strength steels. A Marciniak-type biaxial stretching test of the four classes of high strength steels was carried out to measure the material damage limit of Cockcrofi-Latham fracture criterion. Furthermore, in order to improve the simulation accuracy, the local anisotropic parameters depending on the plastic strain (strain dependent model of anisotropy ) were measured by digital image correlation method and incorporated into Hill' s anisotropic yield condition by authors. To confirm the validity of Cockcrofi-Latham fracture criterion, the uniaxial tensile tests based on JIS No. 5 tensile specimen were performed. The force-displacement history and fracture happening strokes were predicted with high accuracy. Then, Cockcrofi-Latham fracture criterion was applied to predict the failure of four types of spot welded joints. To simulate the local bending and warping deformations around the heataffected zone, the discrete Kirchhoff triangle element was adapted. FEM results for four classes of high strength steels and four types of spot welded joints had a good correlation with experimental ones. 相似文献
14.
《Science & Technology of Welding & Joining》2013,18(3):164-170
In this study, pinless friction stir spot welding of 1.8 mm thick 2198-T8 aluminium–lithium alloy plates was carried out. The change of the angle between the nugget edge and the surface, and the relationship between this angle and joint mechanical property were analysed. The results show that the angle increases rapidly initially and then approaches 45°, which is due to the extrusion of nugget material and its flow along the surrounding ‘cold’ metal during welding. The tensile strength is determined by the nugget edge angle and hook defect. Tensile loads reach a higher value when the nugget edge angle approaches 45° but have a slight decrease with the hook angle changing from obtuse to acute. The maximum tensile/shear strength could be 8.57 kN at the rotation speed of 1500 rev min??1 and the dwell time of 12 s. 相似文献
15.
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 σ0.2 = 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. 相似文献
16.
In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability. 相似文献
17.
采用回填式搅拌摩擦点焊技术对7075-T6铝合金进行了点焊试验.对接头进行了显微组织、显微硬度、剪切和十字形拉伸测试.结果表明,接头显微组织可分为焊核区、热力影响区、热影响区及母材;在焊缝中发现了钩状缺陷、孔洞、未焊合、未完全回填及粘连韧带等缺陷;焊缝区显微硬度呈W形分布,焊点中心呈V形分布;在旋转频率为1 400 r/min,焊接时间为4s时,接头的抗剪强度达到最大值125.6 MPa,为母材强度的39.6%;接头的十字形拉伸载荷随工艺参数的变化规律比较复杂,最大十字形拉伸强度可达43.9 MPa. 相似文献
18.
选用3 mm厚的7075–T6铝合金为研究对象,研究了根部带有螺纹的搅拌针对搅拌摩擦焊搭接接头钩状缺陷及拉剪载荷的影响. 结果表明,搅拌针上的螺纹可明显改变焊接过程中的材料流动;塑性材料在搭接面上部集中,挤压搭接界面,焊后搭接接头的钩状缺陷向下弯曲;搭接面处焊核区的宽度较搅拌针的直径明显增大. 因搅拌针端部无螺纹,焊接速度较大时接头底部会由于材料无法及时填充而产生孔洞缺陷. 随着搅拌头焊接速度的升高,搭接接头的拉剪载荷先上升后下降,最高载荷在焊接速度为40 mm/min时取得,为23.333 kN. 相似文献
19.
Guang-Da Sun Li Zhou Ren-Xiao Zhang Ling-Yun Luo Hao Xu Hong-Yun Zhao Ning Guo Di Zhang 《金属学报(英文版)》2020,33(4):551-560
Refill friction stir spot welding was employed to produce 6061-T6 aluminum alloy joints with different sleeve plunge depths.The interface characteristics of joint-line remnant and hook are investigated by optical and scanning electron microscopy.The joint-line remnant consists of primary bonding region and secondary bonding region,and two types of hook can be identified as downward hook and upward hook.Tensile shear results demonstrate that joint-line remnant and hook make interaction effects on tensile shear properties.The optimal joint is achieved when sleeve plunge depth was 2.0 mm with the corresponding failure load of 8673.4 N.Three different types of fracture mode are exhibited in joints produced at different sleeve plunge depths,which are closely related with the morphology of interface characteristics. 相似文献
20.
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. 相似文献