International Journal of Engineering Trends and Technology (IJETT) – Volume-44 Number-3 -February 2017 Dissimilar Materials of Friction Stir Welding - Overview K. Nagendra Kumar1, P. Ravikanth Raju2 1Asistance Professor, Department of Mechanical Engineering, Bhaskar Engineering College, Yenkapally, Moinabad (M), R.R.(Dist), Hyderabad-500075, Telangana State, India. 2Department of Mechanical Engineering, Anurag Group of Institutions, Venkatapur (V), Ghatkesar (M), R.R. Dist -500088, Telangana State, India Abstract - Friction Stir Welding is a joining process welding of metal-to-polymer is given greater which involves the deformation of materials. In this emphasis in this section than metal to- metal and process tool will generate the pressure and polymer-to-polymer welding, since metal-to- temperature and form solid state weld. This process polymer is a novel technique and there are fewer is suitable for joining different materials, different publications in this area [15]. The schematic mechanical and chemical properties, and different representation of FSW process is shown in Fig. material structures. Fusion welding processes 1. exhibits poor weldability by Welding of dissimilar aluminium alloys. Because of thin oxide layer formation, oxide layer tends to thicken at higher temperatures on the surface of aluminium alloys. This review addresses the Friction stir welding overview which includes the basic concept of the process, microstructure formation, influencing process parameters, typical defects in FSW process and some recent applications. The paper will also discuss some of the process variants of FSW such as Friction Stir Processing. Keywords - Tool rotational speed, Friction Stir welding, dissimilar aluminium alloy. 1. INTRODUCTION Fig 1: FSW Process [14] FSW was invented in UK in December, 1991 at The shoulder is pressed against the surface of the The Welding Institute (TWI). FSW is a new solid materials being welded, while the probe or pin is state welding technology that has created a forced between the two components by a downward worldwide attraction especially in automobile and force. The rotation of the tool under this force aerospace industries as compared to conventional generates a frictional heat that decreases the fusion welding techniques for the welding of light resistance to plastic deformation of the material. weight alloys. For reducing the weight of automobiles the use of lightweight material is most 1. FSW of AZ31 Mg Alloy to 6061 Al alloys: effective. The tool rotation and weld direction are Dissimilar friction stir welding between AZ31-O similar on one side called as Advancing Side (AS) Mg and 6061-T6 Al alloys was investigated using 3 and opposite on the other called as Retreating Side mm thick plates of aluminium and magnesium. (RS). Friction stir welding operations were performed at It is big challenge to weld aluminium alloys with different rotation and travel speeds. The rotation the help of conventional fusion welding processes. speeds varied from 600 to 1400 r/min, and the travel Conventional fusion welding techniques are speed varied from 20 to 60 mm/min. Defect-free susceptible to various welding defects like cracks, weld was obtained with a rotation speed of 1000 voids, porosity etc. It’s a matter of concern, because r/min and travel speed of 40 mm/min. Tensile test of thin oxide layer formation, high thermal results indicated that the tensile strength of the conductivity, high coefficient of thermal expansion, welded specimen is about 76% of AZ31 Mg alloy solidification shrinkage and high solubility of and 60% of the 6061 Al alloy in tensile strength hydrogen and other gases in molten state [14]. [15]. Parts made by combining dissimilar materials such as metal-to-metal, polymer- to-polymer, and metal-to-polymer are now days in high demand. The ISSN: 2231-5381 http://www.ijettjournal.org Page 116 International Journal of Engineering Trends and Technology (IJETT) – Volume-44 Number-3 -February 2017 2. The Influences of The Friction Stir Welding on 5. Friction Stir Welding of Dissimilar Aluminium Aluminium 6063 and 7075: Alloys (6061&7075) By Using Computerized Numerical Control Machine: In this research the influence of the friction stir welding on hardness of aluminium 6063 and 7075 Friction stir welding, a solid state joining was studied. The parameters which influence on technique, is widely being used for joining Al alloys welding are rotational speed of 2000 rpm, welding for aerospace, marine automotive and many other speed of 50-200 mm/min and tilt angle pin tool of applications of commercial importance. FSW trials 2°. As the result we found maximum tensile strength were carried out using a computerized numerical is105 MPa for welding speeds to 100 mm/min. For control machine on (Al 6061 & 7075) alloy. The the hardness test results showed that the highest tool geometry was carefully chosen and fabricated to measured hardness is 152 HV at weld centre was have a nearly flat welded interface (cylindrical & welding speed 50 mm/min [6]. taper) pin profile. Important process parameters that control the quality of the weld are a) rotation speed 3. Friction Stir Welded Cast and Wrought (1600&1250rpm) b) traverse speed (120mm/min) Aluminium Alloy Joint: and c) tool tilt angle 2 and these process parameters During the FSW process, the non consumable tool were optimized 0 to obtain defect free welded joints. rotates to plunge and travels along the weld line to The main aim in this work was to find the produce a high quality of joint. FSW process mechanical properties of friction stir welding of eliminates the fusion welding problems such as dissimilar aluminium alloys (6061&7075) by using crack, porosity and solidification shrinkage. The aim CNC vertical milling machine. The limitations of of the work was to evaluate the microstructure and FSW are reduced by intensive research and mechanical properties of friction stir welded development. Its cost effectiveness and ability to AA6061 cast and wrought aluminium alloy joint. In weld dissimilar metals makes it a commonly used FSW, the process parameters such as welding speed welding process in recent times [16]. of 50 mm/min, rotational speed of 800 rpm and axial force of 8 kN was used to make the joint. Two 6. Friction Stir Welding of Aluminium Alloy to samples were welded by keeping one sample of Steel: wrought alloy as an advancing side and cast alloy in Butt-joint welding of an aluminium alloy plate to retreating side and another sample of weld is a steel plate was easily and successfully achieved. produced by keeping the plate alternatively on both The maximum tensile strength of the joint was about sides. The welded samples were characterized by 86% of that of the aluminium alloy base metal. using metallurgical microscopy and universal tensile Many fragments of the steel were scattered in the testing machine [13]. The microstructures of 6061- aluminium alloy matrix, and fracture tended to occur T6 cast Al alloy and 6061-T6 wrought Al alloy is along the interface between the fragment and the shown in Fig. 2. aluminium matrix. A small amount of intermetallic compounds was formed at the upper part of the steel/aluminium interface, while no intermetallic compounds were observed in the middle and bottom regions of the interface. A small amount of intermetallic compound was also often formed at the interface between the steel fragments and the aluminium matrix. The regions where the intermetallic compounds formed seem to be fracture Fig 2: Microstructures of 6061-T6 cast Al alloy (a) and paths in a joint [1]. 6061-T6 wrought Al alloy (b). 7. Tool Geometry on Friction Stir Welding of AA 4. Effect of Heat Input on The Properties of 6061 and Az61: Dissimilar Friction Stir Welds of Aluminium and Friction Stir Welding Process (FSW) is a solid Copper: state welding method developed by The Welding The effect of heat input on the resulting properties Institute (TWI). This research work involves the of joints between aluminium and copper produced friction stir welding of two dissimilar metals namely with the friction stir welding process. The welds AA6061 and AZ61. The geometry of the tool in were produced using three different shoulder Friction Stir Welding (FSW) plays a principle role in diameter tools, viz., 15, 18 and 25 mm by varying quality of the weld. In this study several FSW tools the rotational speed between 600 and 1200 rpm and have been considered for the fabrication of a number the traverse speed between 50 and 300 mm/min in of butt joints. The tool geometry names are as order to vary the heat input to the welds [10]. follows: (i) Straight threaded tool, (ii) Taper Threaded tool, (iii) Inverse tapered tool, (iv) Concave shaped fluted tool. These geometries are ISSN: 2231-5381 http://www.ijettjournal.org Page 117 International Journal of Engineering Trends and Technology (IJETT) – Volume-44 Number-3 -February 2017 analysed for the identification of sound weld through influence of these parameters on the mechanical ANSYS [11]. performance of the weld has been investigated in terms of hardness and tensile testing [20]. 8. Optimization of AA6061-AA7075 Dissimilar 11. Friction Stir Welding of Dissimilar Joint Friction Stir Welding Using The Taguchi Between Semi-Solid Metal 356 and AA 6061- Method: T651 by Computerized Numerical Control In this study, the Taguchi method was utilized to Machine: determine the optimum process parameters for The investigation is on effect of welding dissimilar friction stir welding between AA6061 and parameters on the microstructure and mechanical AA7075 aluminium alloys. The Taguchi L9 properties of friction stir welded butt joints of orthogonal array and optimization approach was dissimilar aluminium alloy sheets between Semi- applied on three levels of three critical factors, Solid Metal (SSM) 356 and AA 6061-T651 by a namely rotational speed, transverse speed and tool Computerized Numerical Control (CNC) machine.