Effects of welding parameters and tool geometry on properties of 3003-H18 aluminum alloy to mild steel friction stir weld

Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding (FSW). A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor (HIF) achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2–0.4, by TMAZ at HIF of 0.4–0.8 and by intermetallics and/or defects at HIF>0.8.     

Microstructural characterization and mechanical properties of aluminum 6061-T6 plates welded with copper insert plate (Al/Cu/Al) using friction stir welding

Friction stir welding was used to join two aluminum 6061-T6 plates with an insert of a pure copper plate (Al/Cu/Al), and then the influence of the copper insert on the joint performance was studied. The dissimilar welding results were also compared with AA 6061 friction stir welds produced without copper insert (Al/Al). Optical and scanning electron microscopes were used for the microstructural observations of the welded samples. X-ray diffraction analysis was used to analyze phase component of the Al/Cu/Al specimen. A defect-free joint was observed for the Al/Cu/Al joint at a rotational speed of 950 r/min and a welding speed of 50 mm/min. Microstructural observation of the weld nugget zone (WNZ) demonstrates the formation of composite-like structure which promotes metallurgical bonding of aluminum and copper. XRD results show the formation of intermetallic compounds (IMCs), such as Al₄Cu₉ and Al₂Cu. Furthermore, it was observed that the hardness of the weld with the Cu insert plate is higher than that of other samples due to more dislocation density and a distinct rise in hardness values was observed due to the presence of IMCs. The ultimate tensile strength of the joint with copper insert plate is higher than that of the other sample due to the strong metallurgical bonding between Al and Cu.     

Effect of welding speed on microstructural and mechanical properties of laser lap weld joints in dissimilar Al and Cu sheets

Conventional fusion welding of aluminium and copper dissimilar materials is difficult because of poor weldability arising from the formation of brittle intermetallic compounds on the weld zone as well as different chemical, mechanical and thermal properties of welded joints. Joining of Al and Cu plates or sheets offers a metallurgical challenge due to unavoidable formation of brittle intermetallic compounds. Therefore, it is necessary to effectively suppress the formation and growth of Al–Cu intermetallic compounds. For welding of dissimilar Al and Cu sheets, no systematic work has been conducted to reduce these defects. Thus, this paper focuses on the effect of welding speed on the quality of a lap weld joint in the Al and Cu sheets with a single mode fibre laser. It was found that consequently sound strong weld joints could be produced by suppressing the formation of intermetallic compounds in the interface zone at extremely high speeds.     

Enhancing metallurgical and mechanical properties of friction stir lap welding of Al–Cu using intermediate layer

Abstract

In this paper, the material behaviour and mechanical characteristics of lap joint friction stir welding (FSW) between dissimilar alloys, namely, Cu and Al, is investigated. In order to produce welds of a higher quality, a layer of Cu is anodised on the aluminium alloy. The mechanical and the microstructural characterisations are performed on the welds, which are produced using various welding parameters. Scanning electron microscope with energy dispersive X-ray spectroscopy is used to identify the elemental compositions of phases that are formed. The results reveal that the use of the copper anodised layer prevented formation of brittle intermetallic compounds due to the direct FSW of 6061 aluminium alloy to copper and, as a result, enhanced the weld metallurgical and mechanical properties.     

Cu/Ti异种金属搅拌摩擦焊搭接接头组织与性能

文中采用搅拌摩擦焊法搭接T2工业紫铜和TA2纯钛,研究了搭接接头的宏观形貌和微观组织结构,并测试了接头力学性能.结果表明,当选用搅拌头旋转频率为800 r/min,焊接速度为40 mm/min的工艺参数配比时,可以获得焊缝表面成形良好,连接界面无缺陷的搭接接头.在焊核区,钛和铜以相间的条带结构形式相互混合、紧密连接在一起,形成了涡流状的钛铜双相金属混合区域,而且某些区域呈现出"机械互锁"的组织形貌.钛铜搭接接头抗剪切力可达到铜母材失效载荷的95%,断裂位置位于搭接接头铜板前进侧,为典型的韧性断裂.     

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.     

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.     

转速对6061铝合金/纯铜异种金属搅拌摩擦焊接头组织与性能的影响

采用搅拌摩擦焊技术对4 mm厚6061-T6铝合金和纯铜进行连接,研究转速对铝铜异种金属接头组织与力学性能的影响。结果表明,当焊接速度为30 mm/min、搅拌头转速在1 200~1 800 r/min的范围内,可以获得表面成形良好、无缺陷的铝铜异种金属接头。大量破碎的铜被搅入焊核区,形成了组织结构复杂的区域。通过EDS和XRD分析,在焊核区内发现了Al_2Cu、Al_4Cu_9和Al Cu金属间化合物。在界面处,铝和铜发生相互扩散形成金属间化合物层,随着转速的提高,化合物层逐渐变厚。由于晶粒细化、固溶强化作用以及金属间化合物的生成,异种接头的焊核区平均显微硬度值高于铝铜两侧平均硬度,并且在焊核区出现硬度峰值点。随着转速的增加,接头抗拉强度呈现先增大后减小的趋势,所得最优接头抗拉强度为183 MPa,达到铜母材的71.8%,断裂位置位于铝侧热影响区,断裂方式为韧性断裂。     

State of the art about dissimilar metal friction stir welding

Friction stir welding is a rather recent welding process (patented in 1991 by Thomas et al., ‘Improvements to friction welding’ UK patent application no. 9125978.8, US Patent 5460317, 1995) that has shown great potential for welding dissimilar materials even of different metallic nature, e.g. Al to steel, Mg to steel, Al to Ti, Mg to Ti, Al to Cu, Al to Mg. This review presents the specific microstructural features and mechanical properties, in particular tensile strength, of such welds. A focus will be on the material flow and welding defects, on the intermetallic compounds, on constitutional liquation, on particularities related to dissimilar lap welding and finally on process modifications to improve dissimilar friction stir weldability.     

Dissimilar friction stir welding between 5052 aluminum alloy and AZ31 magnesium alloy

Dissimilar friction stir welding between 5052 Al alloy and AZ31 Mg alloy with the plate thickness of 6 mm was investigated. Sound weld was obtained at rotation speed of 600 r/min and welding speed of 40 mm/min. Compared with the base materials, the microstructure of the stir zone is greatly refined. Complex flow pattern characterized by intercalation lamellae is formed in the stir zone. Microhardness measurement of the dissimilar welds presents an uneven distribution due to the complicated microstructure of the weld, and the maximum value of microhardness in the stir zone is twice higher than that of the base materials. The tensile fracture position locates at the advancing side (aluminum side), where the hardness distribution of weld shows a sharp decrease from the stir zone to 5052 base material.     

Effect of Shoulder Size on Weld Properties of Dissimilar Metal Friction Stir Welds

This article reports a research study that shows the effect of shoulder diameter size on the resulting weld properties of dissimilar friction stir welds between 5754 aluminum alloy (AA) and C11000 copper (Cu). Welds were produced using three different shoulder diameter tools: 15, 18, and 25?mm by varying the rotational speed between 600 and 1200?rpm and the traverse speed between 50 and 300?mm/min to achieve the best result. Each parameter combination was chosen to represent different heat input conditions (low, intermediates and high). The welds were characterized through microstructural evaluation, tensile testing, microhardness measurements, x-ray diffraction analysis, and electrical resistivity. Microstructural evaluation of the welds revealed that the welds produced consisted of all the friction stir welding (FSW) microstructure zones with organized flow lines comprising mixture layers of aluminum (Al) and copper (Cu) at the Stir Zones. The average Ultimate Tensile Strength (UTS) of the welds considered ranged from 178 to 208?MPa. Higher Vickers microhardness values were measured at the joint interfaces of all the welds because of the presence of intermetallic compounds in these regions. The x-ray diffraction analysis revealed the presence of Al₄Cu₉ and Al₂Cu intermetallics at the interfacial regions, and low electrical resistivities were obtained at the joint interfaces. An optimized parameter setting for FSW of Al and Cu was obtained at the weld produced at 950?rpm and 50?mm/min with the 18-mm shoulder diameter tool.     

温度峰值影响6061铝/AZ31B镁异种材料FSW接头成形的规律

以6061-T6铝合金与AZ31B镁合金为研究对象,基于Abaqus软件进行了异种材料搅拌摩擦焊过程的温度场数值模拟,重点分析搅拌针偏置镁侧下的搅拌区温度峰值影响焊缝表面成形的规律。结果表明,当焊接温度峰值高于Al-Mg共晶温度时,搅拌针根部附近区域会出现较明显的黏着现象,其随着焊接速度的降低而加剧,这与焊接温度峰值的升高相关。随着焊接速度的增加,焊缝表面更易避免裂纹缺陷的产生。当搅拌头的转速为1200r/min且焊接速度为40mm/min时,6061铝/AZ31B镁异种材料焊接接头的表面成形良好。     

Materials flow and phase transformation in friction stir welding of Al 6013/Mg

Material flow and phase transformation were studied at the interface of dissimilar joint between Al 6013 and Mg, produced by stir friction welding (FSW) experiments. Defect-free weld was obtained when aluminum and magnesium were placed in the advancing side and retreating side respectively and the tool was placed 1 mm off the weld centerline into the aluminum side. In order to understand the material flow during FSW, steel shots were implanted as indexes into the welding path. After welding, using X-ray images, secondary positions of the steel shots were evaluated. It was revealed that steel shots implanted in advancing side were penetrated from the advancing side into the retreating side, whereas the shots implanted in the retreating side remained in the retreating side, without penetrating into the advancing side. The welded specimens were also heat treated. The effects of heat treatment on the mechanical properties of the welds and the formation of new intermetallic layers were investigated. Two intermetallic compounds, Al₃Mg₂ and Al₁₂Mg₁₇, were formed sequentially at Al6013/Mg interface.     

Microstructure,mechanical properties and failure behaviour of protrusion friction stir spot welded 2024 aluminium alloy sheets

The current study investigates the mechanical and microstructure properties of 2024 aluminium alloy welded by protrusion friction stir spot welding as a novel method to produce keyhole-free welds. Tool rotation speed and anvil protrusion height are used as effective variables of the process to obtain optimum conditions. Results illustrate that the keyhole-free welds with the joint show superior mechanical properties in protrusion friction stir spot welding compared to conventional friction stir spot welding. Failure mode changes from interfacial mode to circumferential mode by increasing the nugget zone depth and joint length, while the effect of nugget zone is considerable. Finally, welding at a rotation speed of 1600?rev?min^?1 and a protrusion height of 0.4?mm presents significant mechanical properties with more joint length.     

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.     

Repair welding process of friction stir welding groove defect

The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain an optimum repair welding process. The experimental results indicate that the groove defect can be removed by friction stir repair welding, and the offset repair welding process is superior to the symmetrical repair welding process. In the symmetrical repair welding process, a large number of fine cavity defects and an obvious aggregation of hard-brittle phase Al2Cu occur, accordingly the mechanical properties of the repair joint are weakened, and the fracture feature of repair joint is partially brittle and partially plastic. A good-quality repair joint can be obtained by the offset repair welding process, and the repair joint is fractured near the interface between the weld nugget zone and thermal-mechanically affected zone.     

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%.     

异种铝合金单层板与双层板对搭接搅拌摩擦焊

将一块厚4 mm的LF5铝板与两块厚2 mm的6063铝板组成并种铝合金对搭接复合接头,进行搅拌摩擦焊工艺试验并优化焊接参数,获得优质焊缝.重点研究搅拌头转速、搅拌针偏移量对复合接头抗拉强度的影响,并对焊缝表面及横截面宏观形貌、焊缝“洋葱环”组织形貌、焊缝缺陷等进行观察.分析在搅拌针选取不同偏移量的条件下,双层板一侧的...     

Tensile properties and mechanical heterogeneity of friction stir welded joints of 2014 aluminum alloy

1 INTRODUCTIONFriction stir welding ( FSW) is a new andpromising welding process that can produce low-cost and high-quality joints of many alloys[1 7]becauseit does not need consumable filler materialsand can eli minate some welding defects such ascrack and porosity . In the FSW process , thewelding temperature is lower than that in thefusion welding, and the metal is in the plasticstate ,so many fusion welding defects can be avoi-ded. At present , more and more researches havebeen focu…     

2014铝合金搅拌摩擦焊接头缺陷分析

采用搅拌摩擦焊方法对8mm厚的2014铝合金进行了焊接，分析了接头缺陷的种类及形成原因。研究结果表明：搅拌头形状及焊接工艺参数对接头缺陷的形成具有重要影响；缺陷主要有孔洞、裂纹、飞边和沟槽四种；焊接缺陷的产生是由于在搅拌摩擦焊接过程中焊缝金属经历了不同的热机过程所致，过热或者塑性材料流动不足都会导致焊接缺陷的形成。