Papers by Keyword: Friction Stir Welding (FSW)

Abstract: Microstructure characterization and defects formation of a joint fabricated by friction stir welding on two plates of Al 6061 were studied. In this study, plates were in the height of 2mm and input parameters were pin profile (square and cylindrical shape), rotating speed (800 and 1600 rpm) and traverse speed (40, 80 and 120 mm/min). Also, some experiments were conducted and the effects of input variables on the microstructure of the samples are studied by using an optical microscope. Based on the results, a sound defect-free weld could be achieved by optimizing the ratio of traverse speed to rotational one, due to the influence of this ratio on the amount of heat generated during the FSW process. It has been also concluded that higher ratios of traverse speed to rotating speed can result in poor welds.

Abstract: By means of optical and scanning electron microscopy the surface layer structure of aluminum alloy AMg5 samples with introduced copper part after adhesive frictional contact with AISI 420 steel counterbody was studied. It is revealed that under plastic deformation and material fragmentation in the frictional contact zone a complex mixture of different phase layers is formed due to the formation of different flows of aluminum alloy and copper during friction. Mechanical mixing of a material occurs on all length of a friction path with different intensity depending on distance to copper fragment. Both laminar and turbulent flows of material are formed in the surface layer, as well as a wide range of solid solutions, intermetallic phases and mechanical mixtures.

Abstract: The paper presents the results of experimental development of the technology of friction stir welding to obtain a nonseparable connection of a special aerospace aluminum, titanium and magnesium alloys, high-temperature steels. Regularities and models of heat balance in the welding zone have been determined, which make it possible to predict the technological possibilities of high-speed friction welding. It is established that high-speed friction welding by mixing allows to obtain a high-quality connection at lower loads on the design of the equipment. On the basis of studies of macro-and microstructure, microhardness, level of residual stresses and strength tests, technological recommendations on the choice of welding conditions and conditions were obtained. Presented of experimental and industrial development of special equipment, high-speed friction welding, design and manufacturing of high hardness tools of complex spatial shapes for welding aircraft materials.

Abstract: The paper present some general aspects regarding results obtained by ISIM Timișoara at FSW of steel alloys, with wide use in important industrial fields. The paper also contains information on own contributions of ISIM Timișoara in the field of FSW.Until the present, ISIM Timisoara has responded to some specific requests from the industry, for applying of the FSW process to light alloys and industrial copper Cu 99.The paper presents some general elements regarding the results obtained to welding steels having wide use in industry and which can substantiate industrial applications.The experimental welding programs were developed using the techniques of application of the FSW process, made by ISIM Timisoara: FSW welding machine, welding tools for steels, monitoring systems of the welding process FSW, respectively system for applying of the FSW-TIG hybrid welding process.Sintered tungsten carbide P20S tools with smooth shoulder and pine in 3 constructive variants: smooth conical, smooth cylindrical and pine with four flat recesses (pyramid trunk) were used.It has been shown that the welding tools made of P20S tungsten carbide, with sharp edges, are more resistant and present the best solution for FSW applications.Experimental programs have shown that by observing specific process conditions, the FSW process can be applied with excellent results when welding steel.

Abstract: Experiments have been performed for the butt welding of 160 mm x 90 mm x 2 mm sheets of EN AW 5754 aluminium alloy, where the friction stir welding (FSW) has been used.Referring to the parent metal, the chemical composition and the form of wrought products of the aluminium alloy EN AW 5754 is presented, according to the standard EN 573-1:2005, respectively EN 573-3:2013. The mechanical properties of EN AW-5754 (Al Mg3) sheets are presented, according to EN 485-2:2016. The experiments have been conducted on the own equipment for friction stir welding, type FSW-4kW-10kN, to execute 8 (eight) FSW test pieces, according to EN ISO 25239-4. A quenched FSW tool, own-made of C 45 grade steel, EN 10083, has been used. The parameters of the FSW tests are shown. As main parameters, the rotational speed of the FSW tool was in the range n = 800 – 1200 rev/min, respectively the travel speed was in the range v = 50 – 200 mm/min. The run of the joining experiments is described and the joining test pieces are presented in figures. The ultimate tensile strength of the parent metal (σ_min,pm) is based on the specified minimum tensile strength of the ”O” condition of the parent material, respectively this value is also required for the weld, that is σ_min,w = 190 MPa. The specimens T1.0, T1.1, T2.1, T2.2, T3.1, T3.2, T4.1, T4.2, T5.1, T5.2 și T6.1 are adequate and accepted by this tensile test. The specimens T1.2, T6.2, T7.1, T72. and T8.1 can be accepted, if higher properties are achieved with a full postweld treatment. Another possibility is a lower extent of the minimum tensile strength of the weld that shall be in accordance with another design specification, for example σ_min,w = 145 MPa. By the correlation of the FSW parameters with the results of the tensile test, the ranges for the main parameters with adequate values of the ultimate tensile strength are established: n = 800 – 1000 rev/min and v = 50 – 100 mm/min. By the conclusions, the main aspects of the execution of the FSW test pieces, as well as the results of the tensile tests are selected. The involved industrial areas of the applications are: electro-technique, electronics, manufacturing, shipbuilding and automotive industries. The FSW process is ecological, because it neither uses, nor produces hazardous substances. The references consist of 12 titles.

Abstract: This article presents the effect of weld zone shapes on microstructure and tensile properties of weld joints in friction stir welding. Experiments are conducted using four different tool pin profiles that are cylindrical, conical, cylindrical-conical and stepped-conical for analysing the weld zone shape. The weld zone shape properties are defined by characteristic length. Grain size and mode of fracture surface behavior are analysed by optical microscope and scanning microscope respectively and tensile strength is measured by universal testing machine. It is also observed that the weld zone shape of all pin profile tool is vase shape. In which, cylindrical, conical and cylindrical-conical pin profile tools produce basin dominant vase shape and stepped-conical pin profile tool produces cylinder dominant vase shape. The experimental result shows that the weld joint fabricated by stepped-conical pin profile tool produces the smallest grain, good ductile fracture mode and highest tensile properties as compared to other pin profile tool. This analysis shows that cylinder dominant vase shape produces high tensile properties and enhance ductile fracture mode in the weld joint.

Abstract: In recent years, increasing weld strength along with improved surface properties of the joint during friction stir welding (FSW) has gained noteworthy attention due to increasing applications concerning higher wear resistance and strength related factors. Accordingly, the exploration endures for new materials and ways which will probably increase weld strength along with imparting various improved surface properties to the weld. In spite of several modifications on FSW, its in-situ composite fabrication potential remains quite unfamiliar. In this study, we make available an up to date review of recent in-situ fabricated composites during FSW by using various reinforcements. In particular, the effect of various reinforcements and methodology on the weld strength and surface hardness is reported systematically. Moreover, the strengthening mechanisms accountable for the improvement in weld propeties have been reviewed, and the new potential applications of this new welding strategy are envisaged.

Abstract: In this study, multi objective optimization for improving the joining characteristics of dissimilar AA5083-AA6061 alloys during FSW has been presented. Tool rotational speed, feed and tilt angle are the input parameters whereas tensile strength and hardness are the responses. Experiments are planned and conducted as per Taguchi L₉ orthogonal array. Main effects plot and contour plot discloses the parametric influence over the responses. Hybrid GRA and PCA were deployed as tools to perform multi objective optimization. Results pointed out the fact that tilt angle played vital role in affecting the responses followed by feed and tool rotational speed. The optimum parametric settings obtained are speed 710 rpm, Feed 50 mm/rev, and Tilt angle 2^o.

Abstract: This paper reports friction-stir forming (FSF) of gear-racks of JIS A5083 aluminum alloy with semi-closed dies. FSF is a modified friction-stir process suggested by Nishihara in 2002. The process generates frictional heat and internal forces, enabling massive deformation of the material. It has been successfully utilized for mechanical joining and microforming, but seems to offer an opportunity for net-shape forming of bulk products as well. We put a material in a semi-closed gear-rack die and conducted friction stirring on its top surface. The material deformed and filled the cavity of the die due to high pressure and heat caused by friction stirring. This study investigates the forming conditions and the corresponding results, including the material fill ratio in the tooth. We also investigated the difference between this method and open-type FSF that had been conducted with an open-die structure.

Abstract: This study was conducted to investigate fatigue behavior of friction stir welding (FSW) butt joints for 6156-T6 aluminum alloy. The detail fatigue rating (DFR) values of 6156-T6 FSW joints is obtained based on statistical analysis of fatigue tests. The micrographs of weld structure were observed by optical microscope (OM), Fatigue fractography was researched under scanning electron microscope (SEM). The results indicate that DFR value of 6156-T6 FSW joints is 153.31MPa. Fatigue property of FSW butt joints is sensitive to the microstructural features, such as nugget zone (NZ), thermo mechanically affected zone (TMAZ) and heat affected zone (HAZ). The hardness distributions of the FSW joints reveal W-shaped profiles. Fractography shows that fatigue cracking is initiated at weak-bonding defects, which are located at the root site of the butt joint. The weak-bonding defects have obvious influence on the fatigue properties of friction stir welding.