Friction Stir Welding on Dissimilar Metals Aluminum Alloy to Cuzn34 Brass
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Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-5, 2017 ISSN: 2454-1362, http://www.onlinejournal.in Friction Stir Welding On Dissimilar Metals Aluminum Alloy to CuZn34 Brass 1 K.Dayanand, & 2A.Joshi Gowri Shankar Asst. Professor, Mechanical Engineering, Swamy Vivakanadha Institute of Technology Abstract: In friction stir welding (FSW) a automated. It is also a cleaner and more efficient cylindrical, shouldered tool with a profiled probe is process compared to conventional techniques. rotated and slowly plunged into the joint line between two pieces butted together. The parts have to be clamped onto a backing bar in a manner that prevents the abutting joint faces from being forces apart. Frictional heat is generated between the wear resistant welding tool and the material of the work pieces This causes the latter to soften without reaching the melting point and allows traversing of the tool along with weld line. In this research, lap joining of aluminum alloy and BrassZn34 brass was produced by friction-stir welding during which the aluminum alloy sheet was placed on the BrassZn34. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis, and energy- dispersive X-ray spectroscopy (EDS) analysis were used to probe the microstructures and chemical compositions. In addition, the mechanical properties Fig.1. Schematic diagram of the of each sample are characterized using both shear and hardness tests. The optimum parameters resulted Friction Stir Welding process [2] in no visible welding cracks and defects. A dark area in the Al/BrassZn34 interface contained inter It was realized in the development of the FSW metallic compound. In addition, the results show that process that the tool design is critical in producing using high rotational speeds or low traverse speeds sound welds [3]. A basic and conventional design causes the growth of the interfacial inter metallic for a FSW tool is shown in Fig. 2 which consists of area. a threaded pin and a concave shoulder. FSW tools follow the same basic trends in terms of their 1. Introduction shapes and geometries. They are generally comprised of three generic features including a In late 1991 a very novel and potentially world shoulder, a probe also known as a pin and external beating welding method was conceived at TW1. The features on the probe. process was duly named friction stir welding (FSW), and TWI filed for world-wide patent protection in December of that year. TWI (The Welding Institute) is a world famous institute in the UK that specializes in materials joining technology. Consistent with the more conventional methods of friction welding, which have been practiced since the early 1950s, the weld is made in the solid phase, that is, no melting is involved. Compared to conventional friction welding. FSW uses a rotating tool to generate the Fig.2. A Schematic View of FSW Tool necessary heat for the process. Since its invention, (Timothy) the process has received world- wide attention and today two Scandinavian companies are using the FSW joints usually consist of different regions as technology in production, partiBrasslarly for joining illustrated in Fig. 3 following the terminologies used aluminum alloys. Also, FSW is a process that can be by Thread gill [5] which include; the unaffected Imperial Journal of Interdisciplinary Research (IJIR) Page 1109 Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-5, 2017 ISSN: 2454-1362, http://www.onlinejournal.in material or parent metal, the Heat-Affected Zone is determined based on the material being Brasst. (HAZ), the Thermo Excessive spindle speed will cause premature tool wear, breakages, and can cause tool chatter, all of 2.WORKING PRINCIPLE which can lead to potentially dangerous conditions. In friction stir welding (FSW) a cylindrical, Using the correct spindle speed for the material and shouldered tool with a profiled probe is rotated and tools will greatly affect tool life and the quality the slowly plunged into the joint line between two pieces surface finish. The speed at any point on the butted together. The parts have to be clamped onto a periphery (outside edge) of a Brasstter must always backing bar in a manner that prevents the abutting be equal to the ideal speed for the material for it to joint faces from being forces apart. Frictional heat is work at its optimum performance. The spindle generated between the wear resistant welding tool speeds may be calBrasslated for all machining and the material of the work pieces Thiscauses the operations once the welding speed is known. The latter to soften without reaching the melting point best speed depends on the following conditions. and allows traversing of the tool along with weld 1. Weld strength and quality of the weldment line. The maximum temperature reached is of the required- Higher quality of weld and strength can be order of 0.8 of the melting temperature of the obtained at high speed operations. material. The plasticized material is transferred from 2. Material to be welded – Hard material required the leading edge of the tool to the trailing edge of the high speed operation. tool probe and is forged by the intimate contact of 3. Size of weld . Large welds require low speed the tool shoulder and the pin profile. It leaves a solid operation. phase bond between the two pieces. The process can 4. Thickness of the work piece to be welded. be regarded as a solid phase keyhole welding 4. Feed Rate technique since a hole to accommodate the probe is Feed rate is the velocity at which the generated, then filled during the welding sequence. Brasstter is fed, that is, advanced against the work (a) The process uses a rotating non-consumable pieced. It is expressed in units of distance per weld tool that plunges into the base material and revolution for turning and boring (typically inches moves forward. Friction heat caused by the rotating per revolution (ipr) or millimeters per revolution). It pin creates a plasticized tubular shaft around the pin. can be expressed thus for milling also, but it is often Pressure provided by the weld tool forces the express in units of distance per time for milling plasticized material to the back of the pin, cooling (typically inches per minute (ipm) or millimeters per and consolidation. Al alloy is diffiBrasslt to weld by minute). traditional methods, due to high thermal 5. Depth of Penetration conductivity, resulting in defects like porosity, cracks Depth of penetration depends upon the etc. Hence FSW is being increasingly used. The thickness of the material to be welded. It is expressed process is especially well suited to butt and lap joint in units of millimeters (mm). in aluminum since aluminum is diffiBrasslt to weld by are process, but is very simple to weld by FSW. MATERIAL SUITABILITY TWI (The Welding Institute) has 3.VARIABLES IN FRICTION STIR WELDING concentrated most of its efforts to The use of Friction FSW involves complex material movement Stir Welding (FSW) continues to grow. It is now a and plastic deformation. Welding parameters, tool mature process for joining aluminium and is seeing geometry, and joint design exert significant effect on repaid progress in many other engineering alloys. the material flow pattern and temperature Numerous organizations have benefitted from the distribution, there by influencing the micro economic advantages of the FSW process, and this structural evolution of material. In this section, a few symposium will provide the latest information from major factors affecting FSW/FSP process, such as industrial and academic experts from around the tool geometry, welding parameters, joint design are world in this and related technologies optimizing the addressed. The strength of Friction stir welding process for the joining of aluminium and its alloys. depends on the following three process parameters. Subsequent studies have shown the cast to cast and They are cast to extruded (wrought) combinations in similar 1. Spindle speed and dissimilar aluminium alloys are equally possible. 2. Feed rate The following aluminium alloys could be 3. Depth of penetration successfully welded to yield reproducible high integrity welds within defined parametric to clearances: Spindle Speed 2000 series aluminium (A1-Brass) The spindle speed is the rotational frequency of the spindle of the machine, measured in 3000 series aluminium (A1-Mn) revolutions per minute (RPM). The preferred speed Imperial Journal of Interdisciplinary Research (IJIR) Page 1110 Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-5, 2017 ISSN: 2454-1362, http://www.onlinejournal.in 4000 series aluminium (A1-Si) 10. MECHANICAL CHARACTERIZATION 5000 series aluminium (A1-Mg) The knowledge of the mechanical properties of the 6000 series aluminium (A1-Mg-Si) dissimilar friction stir welds between aluminium and 7000 series aluminium (A1-Zn) brass is of importance to enhance their use in the 8000 series aluminium (A1-Li) industries. Research have found that the maximum Ultimate 6. OTHER MATERIALS TensileStrength achieved in FSwelds of aluminium The technology of friction stir welding has and brass was about 296 MPa and it was obtained been extended to other materials also, on which when the tool rotational speed is 950 rpm, and the researches are going on. Some of them are as travel speed is 150 mm/min [13]. Akinlabi [36] also follows- measured the tensile test using different welding Brass and its alloys parameters, the results showed that the welds Lead produced had Weld joint efficiencies of between 73 Titanium and its alloys and 86%, and can be acceptable for design purposes. Magnesium and its alloys Galvao et al [34] stated that the welding condition, specifically the rotational speeds and the traverse Zinc speeds that results in obtaining welds with good Plastics surface appearance do not lead to the production of Mild steel sound dissimilar welds.