Orbital friction stir lap welding in tubular parts of aluminium alloy AA5083

In this study, orbital friction stir lap welding of 360?mm diameter AA5083-H321 tube to 350?mm diameter AA5083-O flange was investigated. The influence of rotational and travel speed of tool with triangular frustum pin on the metallurgical structure and mechanical properties of orbital friction stir lap welded samples were studied. The results indicated that defect free orbital lap joints are successfully obtained using tool rotational speed of 650 and 800?rev?min^?1 with a constant travel speed of 40?mm?min^?1. The strengthening mechanism in the stir zone is solid solution strengthening and dislocation looping. The maximum joint strength was achieved at a welding speed of 650?rev?min^?1 and 40?mm?min^?1. Failure of tensile shear test samples occurred far from the friction stir welding zone.     

Joint characteristics and dissimilar materials joining of pure-Al/5083 by friction stir welding

Friction stir welding (FSW)^1,2, developed in 1991 by The Welding Institute, UK is a joining process which overthrew welding concepts which existed at the time; its application has been progressed not only for soft alloys including aluminium, but also, in recent years, for steel.³ Sato and others carried out friction stir welding on 1080-O and 5083-O materials and investigated variations in the hardness.⁴ Ten years or so have passed since the development of friction stir welding, the process has been globally investigated and widely employed in various sectors such as vehicles, ships and the aerospace industry. Furthermore, investigations have also been carried out into the manufacture of dissimilar metal joints. For example, Enomoto studied 2024/AC4C cast alloy and reportedly obtained satisfactory joints.⁵ Li and others have investigated 2024/6061 and reported that both alloys are distributed at the weld zone in a stratified and complex manner.⁶     

Variations in stir zone and thermomechanically affected zone of dissimilar friction stir weld of AA5083 and AA6082 alloys

Variations in composition, microhardness (in the thermomechanically affected zone) and texture in the tool domain of the dissimilar friction stir weld of AA5083-O and AA6082-T6 alloys were investigated. The contents of the major alloying elements in the weld zones were determined using inductively coupled plasma?atomic emission spectroscopy. It was observed that a slight drop in the content of the alloying elements results from the friction stir welding process with the Mg content being the most affected amongst the major alloying elements in the two alloys. By relating the mass fractions of the major alloying elements in the parent metals of both alloys to those of the stir zone, the relative proportions of the two alloys in the stir zone were estimated with the results showing that at least 60% of the materials in the stir zone are from the retreating side of the weld. It was also revealed that the changes in the hardness profile in the thermomechanically affected zone of the retreating side are predominantly influenced by changes in grain size in that domain. Finally, the investigation further revealed that the texture component in the tool shoulder domain is different from the texture component in the tool pin domain.     

Force generation during friction stir welding of AA2024-T3

Force measurement in friction stir welding (FSW) provides a significant insight into the process in terms of machine and tool limitations and design. In the present research the tool forces were investigated experimentally using a rotating component dynamometer and through the development of a finite element model. The model correlated well with experimental temperatures and tool forces and was capable of predicting tool forces for different welding parameters, predicting regions were tool failure is likely to occur and identifying tool pin designs which can process the workpiece more efficiently.     

搅拌摩擦焊接工艺参数对AA6061-B4C焊接接头抗拉强度的影响（英文）

搅拌摩擦焊(FSW)是一种固态连接技术,可用来连接高强度铝合金及多种陶瓷颗粒增强金属基复合材料(MMCs)。搅拌摩擦焊获得的陶瓷增强金属基复合材料焊缝优良,在增强体与基体间没有发生有害反应。对搅拌摩擦焊接工艺参数对AA6061-B4C焊接接头抗拉强度的影响进行研究。采用4因素5水平的中心复合设计来控制实验的次数。构建一数学模型来分析搅拌摩擦焊工艺参数对接头抗拉强度的影响。结果表明,在旋转速度1000r/min、焊接速度1.3mm/s、轴向力10kN、增强相含量12%的条件下,搅拌摩擦焊得到的焊接接头的抗拉强度最大。根据构建的模型采用广义简约梯度算法进行优化以得到最大的抗拉强度。金相分析表明,在焊接接头中出现了多种区域,如焊合区、热力影响区和热影响区。在焊合区观察到大量的被细化的铝基体晶粒以及粒径明显减小的B4C颗粒。在热力影响区出现塑性变形、热影响和被拉长的铝晶粒。     

5083铝合金搅拌摩擦焊接头微弧氧化表面防护

采用微弧氧化技术在5083铝合金搅拌摩擦焊接头表面制备一层均匀的陶瓷膜。通过扫描电镜（SEM）、X射线衍射（XRD）和显微硬度测试分析了微弧氧化膜的形貌、相组成和显微硬度,并采用浸泡方法研究了微弧氧化膜对焊接接头耐腐蚀性能的影响。结果表明,接头表面微弧氧化膜均匀致密,铝合金焊缝区的显微硬度低于母相区,但微弧氧化膜的硬度比铝合金基体提高一个数量级,并且不同区域对应的微弧氧化膜硬度相同。在0.2 mol/L NaHSO3＋0.6 mol/L NaCl溶液中浸泡3天后,未氧化处理的焊接样品表面出现孔蚀,而微弧氧化处理的样品表面没有观察到腐蚀迹象。     

Microstructure and mechanical properties of friction stir welded aluminium alloys with special reference to AA 5083 and AA 6082

Abstract

Aluminium alloys AA 5083 and AA 6082 have been friction stir welded and the mechanical properties and microstructures of the welds have been evaluated. Alloy AA 5083 mainly fractured near the centre of the weld, while fracture in AA 6082 mainly occurred in the heat affected zone. The tensile strength of welded joints in AA 6082 was lower than the base material strength, but still met classification societies' requirements. Hardness was approximately constant across the welded zone in AA 5083, while a minimum in hardness was found in the AA 6082 welds. The location of the fracture closely matched the minimum hardness region. Very fine scale precipitation in AA 6082 was significantly affected by the weld thermal cycle. In the zone of lowest hardness, the hardening precipitate (β″-Mg₅Si₆) had transformed to the non-hardening β′-Mg_1.7Si. This is probably the main reason for the minimum in hardness, the fracture location, and the decreased tensile strength. Results are compared to a similar investigation of aluminium alloy AA 7075.     

AA5083铝合金的搅拌摩擦焊接工艺参数对搅拌头受力和热输入的影响(英文)

采用系统实验设计方法研究AA5083铝合金搅拌摩擦焊接工艺参数对搅拌头受力和热量输入的影响,得到了用来设计搅拌摩擦焊搅拌头和焊机的经验模型。当采用计算机来控制搅拌摩擦焊接时,这些模型可用来确定AA5083这类铝合金的摩擦焊接工艺参数、编制焊接程序及工艺参数控制。结果表明:影响轴向力和热量输入的重要参数是搅拌头转速、焊接速度和搅拌头轴肩直径,而影响纵向应力的重要参数是焊接速度和探头直径。     

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。     

Knowledge discovery for friction stir welding via data driven approaches

Abstract

For a comprehensive understanding towards friction stir welding (FSW) which would lead to a unified approach that embodies materials other than aluminium, such as titanium and steel, it is crucial to identify the intricate correlations between the controllable process conditions, the observable internal process variables, and the characterisations of the post-weld materials. In Part 1 of this paper, multiple correlation analyses techniques have been developed to detect new and previously unknown correlations between the internal process variables and weld quality of aluminium alloy AA 5083. Furthermore, a new exploitable weld quality indicator has, for the first time, been successfully extracted, which can provide an accurate and reliable indication of the as welded defects. All results relating to this work have been validated using real data obtained from a series of welding trials that utilised a new revolutionary sensory platform called ARTEMIS developed by TWI Ltd, the original inventors of the FSW process.     

Microstructure and wear behavior of AA6061/SiC surface composite fabricated via friction stir processing with different pins and passes

In this investigation,the effects of pin geometry and number of passes on macrostructure,microstructure,wear rate and also microhardness profile of 6061-T6 aluminum alloy surface composites fabricated via friction stir processing(FSP) were discussed by reinforcement particles of silicon carbide(SiC).The results show that after each FSP pass,a modify distribution of SiC particles is acquired and the increase in the number of passes reduces the average grain size in stir zone(SZ).Furthermore,it is discovered that pin geometry and pass number play a dominant role in the grain size of SZ and distribution of SiC particles in SZ.It is found that after each FSP pass,wear rate is improved due to the uniform distribution of SiC particles in surface of Al/SiC composite.Additionally,the results show that the square pin and smooth(straight)cylindrical pin have the highest and lowest resistance to wear,respectively.     

Fabrication of Al/Al2Cu in situ nanocomposite via friction stir processing

The aim of present work is fabrication of Al/Al₂Cu in situ nanocomposite by friction stir processing (FSP) as well as investigation of FPS parameters such as rotational speed, travel speed, number of FSP passes, and pin profile on the microstructure, chemical reaction, and microhardness of Al based nanocomposite. The Al₂Cu particles were formed rapidly due to mechanically activated effect of FSP as well as high heat generation due to Al-Cu exothermic reaction. The microstructure of the nanocomposites consisted of a finer grained aluminium matrix (～15 µm), unreacted Cu nanoparticles (～40 nm), and reinforcement nanoparticles of Al₂Cu. Irregular morphology of Al₂Cu is attributed to the local melting during FSP. Pin diameter has a higher effect on the microstructure and hardness values. The hardness measurements exhibited enhancement by 57% compared with the base metal.     

Themo-elasto-viscoplastic modelling of friction stir welding

Abstract

A coupled two-dimensional Eulerian thermo-elasto-viscoplastic model has been developed for modelling the friction stir welding process. First, a coupled thermo-viscoplastic analysis is performed to determine the temperature distribution in the full domain and the incompressible material flow around the spinning tool. Next, an elasto-viscoplastic analysis is performed outside the viscoplastic region to compute the residual stress. Both frictional heat and plastic deformation heat generation are considered in the model. Furthermore, this is the only known model computing residual stress accounting for plasticity caused by both thermal expansion and mechanical deformation due to material spinning. The computed residual stress is verified by comparing to experimentally measured data.     

Thermal modelling of friction stir welding

The objective of the present work is to present the basic elements of the thermal modelling of friction stir welding as well as to clarify some of the uncertainties in the literature regarding the different contributions to the heat generation. Some results from a new thermal pseudomechanical model in which the temperature-dependent yield stress of the weld material controls the heat generation are also presented.     

搅拌摩擦焊应用及焊接设备简介

介绍了搅拌摩擦焊的工艺过程，分析了搅拌摩擦焊焊缝及焊接过程的优缺点。对搅拌摩擦焊的应用和常用搅拌摩擦焊设备作了简要的描述。     

Effect of welding parameters on mechanical and microstructural properties of AA6082 joints produced by friction stir welding

The effect of processing parameters on mechanical and microstructural properties of AA6082 joints produced by friction stir welding was analysed in the present study. Different welded specimens were produced by employing a fixed rotating speeds of 1600 rpm and by varying welding speeds from 40 to 460 mm/min. The joints mechanical properties were evaluated by means of tensile tests at room temperature. In addition, fatigue tests were performed by using a resonant electro-mechanical testing machine under constant amplitude control up to 250 Hz sinusoidal loading. The fatigue tests were conducted in axial control mode with R = σ_min/σ_max = 0.1, for all the welding and rotating speeds used in the present study. The microstructural evolution of the material was analysed according to the welding parameters by optical observations of the jointed cross-sections and SEM observations of the fractured surfaces were done to characterize the weld performances.     

Simulation of 3D material flow in friction stir welding of AA6061-T6

This paper reports the numerical simulation of the 3D material flow in friction stir welding process by using finite element methods based on solid mechanics. It is found that the material flow behind the pin is much faster than that in front of the pin. The material in front of the pin moves upwards and then rotates with the pin due to the effect of the rotating tool. Behind of the pin, the material moves downwards. This process of material movement is the real cause to make the friction stir welding process continuing successfully. With the increase of the translational velocity or the rotational velocity of the pin, the material flow becomes faster.     

自持式搅拌摩擦焊研究

文中综述了自持式搅拌摩擦焊的研究现状和存在的不足,主要涉及自持式搅拌摩擦焊原理、搅拌头结构、微观组织、温度场以及力学性能等几方面内容。指出了自持式搅拌摩擦焊接头的焊缝成形、温度场分布以及力学性能等特征。在此基础上提出了进一步的研究方向。     

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.