Macrostructures and mechanical properties of ultrasonic-assisted friction stir welding joint of 2024-T3 aluminium alloy

In friction stir welding of aluminum alloys, tunnel defect may occur due to insufficient plastic material flow caused by lower heat input in the weld region. The inadequacy in heat input is due to improper selection of friction stir welding tool and process parameters. Ultimately, such defects degrade the properties of weld and may pose serious concerns towards the integrity and safety of the weld component. In order to improve the properties of weld joints, an ultrasonic-assisted friction stir welding device has been configured where ultrasonic energy is transferred from an ultrasonic unit directly into one of the workpieces near the tool. Using this configuration, ultrasonic-assisted friction stir welding was conducted on 6 mm thick 2024-T3 aluminum alloy sheets. The macrostructure and mechanical properties of these welds were compared with the welds of this alloy prepared by conventional friction stir welding using identical process parameters. The results show that the welding speed can be increased while satisfactory weld quality is still ensured. The ultrasonic energy transferred in this configuration could enlarge the volume of weld nugget zone. Also, the influence of ultrasonic energy on the suppression or elimination of the tunnel defect is quite apparent. However, any beneficial effects of ultrasonic vibration on the tensile strength and the elongation of the joint were less obvious in this configuration.     

AZ91D薄板搅拌摩擦焊

实现了厚度为2.2 mm铸造镁合金AZ91D薄板的搅拌摩擦焊和钨极氩弧焊,分析了搅拌摩擦焊工艺参数对焊接接头成形的影响和接头组织变化,考察了搅拌摩擦焊接头的力学性能.在搅拌头旋转速度为1 380 r/min时得到了比较理想的焊接接头,而1 960 r/min的转速过大.接头不同区域所受的机械力和热量不同,显微组织明显不同.搅拌区晶粒细小,显微硬度和强度都有所提高.搅拌摩擦焊接头力学性能与热输入有关;与氩弧焊接头相比,搅拌摩擦焊接接头的性能更好.     

超声振动对6061-T4铝合金搅拌摩擦焊接头组织和性能的影响

利用自主研制的试验装置,通过工具头将超声振动能量施加在搅拌头前方的待焊工件上,研究了超声振动能量对减少焊接缺陷、改善搅拌摩擦焊接头组织和力学性能的影响.对6 mm厚度6061-T4铝合金板进行了超声振动强化搅拌摩擦焊工艺试验,并与相同工艺条件下的常规搅拌摩擦焊进行了对比.结果表明,超声振动能够减小焊速/转速比较大时的焊缝内部隧道型缺陷,增大材料对接混合区宽度和焊核区体积,细化焊核区和热力影响区微观组织,提高接头抗拉强度和焊核区显微硬度.     

Microstructure and Mechanical Properties of Dissimilar Double-Side Friction Stir Welds Between Medium-Thick 6061-T6 Aluminum and Pure Copper Plates

It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for medium-thick plates due to the inherent high heat generation rate at the shoulder-workpiece contact interface in conventional friction stir welding. Thus, double-side friction stir welding is innovatively applied to join 12-mm medium-thick 6061-T6 aluminum alloy and pure copper dissimilar plates, and the effect of welding speeds on the joint microstructure and mechanical properties of Al/Cu welds is systematically analyzed. It reveals that a sound Al/Cu joint without macroscopic defects can be achieved when the welding speed is lower than 180 mm/min, while a nonuniform relatively thick intermetallic compound (IMC) layer is formed at the Al/Cu interface, resulting in lots of local microcracks within the first-pass weld under the plunging force of the tool during friction stir welding of the second-pass, and seriously deteriorates the mechanical properties of the joint. With the increase of welding speed to more than 300 mm/min void defects appear in the joint, but the joint properties are still better than the welds performed at low welding speed conditions since a continuous uniform thin IMCs layer is formed at the Al/Cu interface. The maximum tensile strength and elongation of Al/Cu weld are, respectively, 135.11 MPa and 6.06%, which is achieved at the welding speed of 400 mm/min. In addition, due to the influence of welding distortion of the first-pass weld, the second-pass weld is more prone to form void defects than the first-pass weld when the same plunge depth is applied on both sides. The double-side friction stir welding is proved to be a good method for dissimilar welding of medium-thick Al/Cu plates.     

20mm厚2219铝合金可回抽搅拌摩擦焊接及接头组织和性能分析

为了解决封闭环缝的焊接匙孔问题,研究了采用可回抽搅拌摩擦焊接进行匙孔消除的焊接工艺. 在厚板可回抽焊接过程中,搅拌针末端的瞬时空腔问题受体积效应影响将更为显著且更难控制. 研究了不同回抽焊接长度下20 mm中厚板2219铝合金可回抽焊接接头的内部质量、组织形貌和力学性能. 结果表明,在焊接速度100 mm/min、搅拌头转速400 r/min的参数组合下,回抽焊接区长度为200 ~ 500 mm时,可获得无内部缺陷的可回抽搅拌摩擦焊焊缝;回抽焊接区接头横截面上存在2个焊核,靠近焊缝上表面的焊核大小随着回抽过程不断减小;一次焊接、重复焊接和可回抽焊接接头的拉伸性能依次降低,且可回抽焊接接头的力学性能随着回抽距离的增长而有所提升;在实际工程应用中回抽距离500 mm为较优的参数选择.     

5A06铝合金静止轴肩搅拌摩擦焊T形接头组织与性能

采用静止轴肩搅拌摩擦焊方法实现了10 mm厚5A06铝合金T形接头的焊接. 通过低主轴转速匹配高焊接速度与高主轴转速匹配低焊接速度两组不同的焊接参数,结合拉伸试验、宏观与微观金相分析、电子背散射衍射(electron backscattered diffraction,EBSD)分析与扫描电镜(scanning electron microscope,SEM)断口分析,研究了热输入对焊接接头力学性能与组织的影响. 结果表明,在两组焊接参数下均可获得无孔洞缺陷的全焊透T形接头,焊缝表面光滑平整,几乎无减薄发生;热输入不同会改变搅拌针与周围材料的摩擦形式,引起焊缝出现弱结合缺陷,并影响接头抗拉强度; 在高主轴转速匹配低焊接速度时,焊缝中心重叠区顶部易产生弱结合缺陷,导致接头抗拉强度较低,为198 MPa,拉伸试样断裂在筋板. 在低主轴转速匹配高焊接速度时,焊缝无缺陷存在,接头抗拉强度为287 MPa, 拉伸试样断裂在底板.     

Mechanical properties of friction stir welded armor grade Al–Zn–Mg alloy joints

The influence of different welding speeds and rotary speeds on the formation and mechanical properties of friction stir weld joints of armor grade aluminum alloy was presented. The developed weld joints were characterized by bend tests, micro-hardness tests, tensile tests, optical and scanning electron microscopies. Mechanical properties (i.e., micro-hardness, ultimate tensile strength and elongation to fracture) increased with the increase in rotary speed or decrease in welding speed. The effect of welding speed on micro-hardness of heat affected zones was more profound than the rotary speeds. The welding speeds and rotary speeds influenced the mechanical properties and their effects on various mechanical properties of the friction stir welded joints can be predicted with the help of regression models.     

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.     

搅拌头机械载荷在搅拌摩擦焊接中的作用的数值分析

利用数值模拟技术分析搅拌头机械载荷在焊接过程中的作用,通过对比只考虑热载荷,考虑热载荷和搅拌头的下压力,综合考虑热载荷、搅拌头下压力和工作扭矩三种条件下的应力,应变和变形,结果发现,搅拌头下压力使焊后残余应力值大幅下降;搅拌头的工作扭矩是焊后残余应力、应变不对称分布的重要影响因素;并且搅拌头机械载荷使得薄板焊后残余变形的模式发生了完全相反的变化,由不考虑搅拌头载荷时的马鞍状变成了反马鞍状.     

焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响

文中研究了转速和热输入特征值WP一定两种条件下焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响. 结果表明,转速一定时,接头抗拉强度随焊接速度的增加呈先增大后减小的趋势;热输入特征值WP一定时,随着焊接速度的增加,接头的抗拉强度持续减小;接头呈现出三种断裂方式,分别为发生于热影响区的Ⅰ型断裂、发生于焊核区的Ⅱ型断裂和发生于热力影响区的Ⅲ型断裂;Ⅰ型断裂和Ⅱ型断裂为韧性断裂;Ⅲ型断裂为包含韧性断裂和脆性断裂的混合型断裂;接头拉伸断裂位置并非总出现在硬度最低处;焊接速度小于1 000 mm/min时,WP ≤ 1有利于提高接头力学性能,而焊接速度大于1 000 mm/min时,WP > 1更有利于提高接头力学性能.     

Numerical studies on controlling of process parameters in friction stir welding

A thermo-mechanical model is developed to predict the material deformations and temperature histories in the friction stir welding (FSW) process. Based on this model, the effects of the welding parameters on temperatures and material behaviors are investigated. Numerical results indicate that the maximum temperature in the FSW process can be increased with the increase of the rotating speed. The increase of the welding speed can lead to the obvious increase of the efficient input power for FSW system. The material particles on the top surface do not enter into the wake and just pile up at the border of the wake at the retreating side and this is the reason for the formation of the weld fash in FSW. Both the increase of the rotating speed and the decrease of the welding speed can lead to the increase of the stirring effect of the welding tool, which can improve the friction stir weld quality. But when the rotating speed is increased, the weld fash becomes more obvious. When the welding speed becomes higher, the rotating speed must be increased simultaneously to avoid any possible welding defects such as void. The simultaneous increase of the rotating and the translating speeds of the welding tool can lead to the increase of the residual stress.     

Investigations on the Effects of the Tool Material,Geometry, and Tilt Angle on Friction Stir Welding of Pure Titanium

Friction stir welding (FSW) parameters, such as tool material, tool geometry, tilt angle, tool rotational speed, welding speed, and axial force play a major role in the weld quality of titanium alloys. Because of excessive erosion, tool material and geometry play the main roles in FSW of titanium alloys. Therefore, in the present work for the first time, tool material and geometry, tool tilt angle, cooling system and shielding gas effects on macrostructure, microstructure, and mechanical properties of pure titanium weld joint were investigated. Result of this research shows that Ti can be joined by the FSW, using a tool with a shoulder made of tungsten (W) and simple pin made of tungsten carbide (WC). The best conditions for welding were use of compressed air as a cooling system, tool tilt angle of 1°, and a stream of Argon as a shielding medium. Investigation on mechanical properties shows that the tensile strength and the yield strength of the welded joint in the best case could be similar to the corresponding strengths of the base metal.     

薄板AA2024铝合金无针搅拌摩擦焊搭接工艺与接头性能

文中研究了2024薄板铝合金无针搅拌摩擦搭接接头形貌及力学性能,分析了工艺参数对接头成形与力学性能的影响.结果表明,工艺参数对接头成形及力学性能影响显著.接头中Hook缺陷对接头性能影响较大.当旋转速度一定时,焊接速度的增大使得焊核深度减小,Hook缺陷尖端趋于圆滑过渡,接头的拉剪强度随之增大.当焊接速度一定时,随着旋转速度的增大,焊核深度先增大后减小,Hook缺陷尖端上翘的严重程度先加重后减弱,拉剪强度先降低后增加.搭接接头上下两板的横向显微硬度曲线都近似"W"形分布,最低值出现在上板的热影响区.     

工艺参数对复合搅拌摩擦点焊接头力学性能的影响

采用LF21铝合金研究了复合搅拌摩擦焊时焊接工艺参数(旋转速度、旋转半径)对焊接接头力学性能的影响.结果表明,当其它焊接参数一定时,焊点的力学性能随着搅拌头旋转速度的增加而增加,当搅拌头的旋转速度增加到1 200 r/min时,焊点的剪切力达到最大值为3.47 kN,随着搅拌头旋转速度的进一步增加,焊点的力学性能开始降低.改变旋转半径,焊点的力学性能随着旋转半径的增加而增加,当旋转半径达到0.5 mm时,焊点的剪切力达到最大值为3.47 kN,然后,随着旋转半径的继续增加,焊点的力学性能开始降低.LF21铝合金的复合搅拌摩擦点焊焊点的微观组织与直插式搅拌摩擦点焊不同的是,在塑性环的边上形成了一个由第二层塑性环形成的"耳朵形"区域.     

Friction stir welding of AZ31 magnesium alloys processed by equal channel angular pressing

Equal channel angular pressing (ECAP) is an effective thermo-mechanical process to make ultrafine grains.An investigation was carried out on the friction stir welding (FSW) of ECAPed AZ31 magnesium alloys with a thickness of 15 mm.For different process parameters,the optimum FSW conditions of ECAPed AZ31 magnesium alloys were examined.The basic characterization of weld formation and the mechanical properties of the joints were discussed.The results show that the effect of welding parameters on welding quality was evident and welding quality was sensitive to welding speed.Sound joints could be obtained when the welding speed was 37.5 mm/min and the rotation speed of the stir tool was 750 r/min.The maximum tensile strength (270 MPa) of FSW was 91% that of the base materials.The value of microhardness varied between advancing side and retreating side because of the speed field near the pin of the stir tool,which weakened the deformed stress field.The value of microhardness of the welding zone was lower than that of the base materials.The maximum value was located near the heat-affected zone (HAZ).Remarkable ductile character was observed from the fracture morphologies of welded joints.     

异种搅拌摩擦焊AA5083-H111和AA6351-T6铝合金的力学和冶金性能(英文)

研究异种搅拌摩擦焊AA5083-H111和AA6351-T6铝合金的微观结构和力学性能。在3种不同的焊接速度(36、63、90 mm/min)下焊接AA5083-H111和AA6351-T6铝合金,分析焊接速度对接头力学和冶金性能的影响。结构表明,与其他焊接速度相比,焊接速度为63 mm/min时接头的力学性能和冶金性能较好。焊缝区由未混合区、机械混合区和混流区组成。所观察到的断裂模式为韧性纤维断裂。     

耐磨铝硅铜合金的双面搅拌摩擦焊

对10 mm厚的铝硅铜合金进行了双面搅拌摩擦焊接,研究了焊接接头的显微组织及力学性能.研究表明,铸态金属晶粒和硅粒子在双面搅拌摩擦焊接过程中得到细化,硅颗粒分布均匀化.反面焊道比正面焊道的晶粒细化和硅粒子均匀化作用更明显.异向焊接的接头强度较低,所有接头均断在焊缝的前进侧.同向焊接的接头强度较高,接头断裂位置取决于焊接参数.选用搅拌头旋转频率为950 r/min、焊接速度为10mm/min的参数焊接时,同向接头表面成形好、内部无缺陷,其强度可达母材的87.4%.     

工艺参数对搅拌摩擦焊洋葱圆环形成的影响

搅拌摩擦焊中焊缝材料的流动对焊件性能有很大影响，洋葱圆环是搅拌摩擦焊焊焊核区中材料流动的集中体现，文中对5mm厚的1060、3003铝合金板材进行了搅拌摩擦焊连接，通过对其焊核区腐蚀后的形貌观察分析研究了不同工艺参数下材料的流动形态，结果表明，工艺参数对搅拌摩擦焊焊核区洋葱圆环的形成有很大影响，采用较高的搅拌头转速和合适的焊接速度可获得稳定，质量良好的搅拌摩擦焊接头。     

铝合金超薄板无倾角微搅拌摩擦焊接头组织性能

以0.5 mm厚LF3薄壁铝合金微搅拌摩擦焊搭接过程为研究对象,采用超小轴肩搅拌工具,研究了其无倾角微搅拌摩擦焊接过程,重点分析了微观组织分布特点和接头力学性能.采用内聚花纹锥形超小轴肩搅拌工具,依靠轴肩及搅拌针花纹的材料内聚效果,降低了焊缝宽度,焊缝宽度仅为3 mm,为微小薄壁壳体的焊接封装问题提供了可行的解决方案.搅拌工具的超高旋转频率运动,将搭接界面进行了充分的搅拌、混合和破碎,优于传统搅拌摩擦焊的Hook搭接界面.微搅拌摩擦焊搭接接头承载能力平均达到母材承载能力的89.6%.     

Friction stir welding of aluminium casting alloys

The results of testing friction stir welding quality in relation to EN AC-43200 (AK9) and EN AC-45000 (AK64) aluminium casting alloys are presented. The test joints were made with the use of a welding machine constructed on the basis of numerically controlled milling machines. The assessment of the joint quality was made based on visual inspection, mechanical testing, weldment structure analysis and hardness tests. The purpose of the investigation was to discover the possibility of friction stir welding of casting alloys and the influence of welding conditions on joint properties and structure. The test results show good weldability of aluminium casting alloys by the FSW method. Sound welds can be obtained in a relatively wide range of welding parameters while the weld strength is satisfactory. In order to obtain the highest quality joints, the workpieces must be pressed onto the other, while the welding process cannot run with excessively high speed. The best mechanical properties of the joints were achieved when the friction process was conducted at a rotational speed of the mixing tool of 900 rpm.