Mechanical and Micro-structural Study of Friction Stir Welding of Al-alloy International Journal of Applied Research In Mechanical Engineering (IJARME), ISSN: 2231 –5950 Volume-1, Issue-2, 2011 Mechanical and Micro-structural Study of Friction Stir Welding of Al-alloy Biswajit Parida * , Sukhomay Pal ** ,Pankaj Biswas *** , M M Mohapatra **** ,Sujoy Tikader ***** *,**,*** Mechanical Engineering, IIT Guwahati, India-781039. **** Mechanical and Industrial Engineering, IIT Roorkee, India-781039. ***** Haldia Institute of Technology, West Bengal, India-721604. Email: b.parida@iit.erner.in Abstract: The present study is on the development of friction stir welding (FSW) of commercial grade Al-alloy to study the mechanical and micro- structural properties. The proposed research will include experiments related to the effect of FSW optimum process parameter on weldability of Al alloy. The present paper has been subdivided in to two different sections: 1. Study of Mechanical properties and 2. Study of micro-structural properties. Section1 describes the tensile strength of welded sample and distribution of micro- hardness in different zones of FSW weld specimen and section2 contains the microstructure characterization of different zones of friction stir welds. Key words: FSW, weldability, mechanical properties, tensile strength, micro-hardness, microstructure. 1 Introduction: The history of joining metals goes back several millennia, with the earliest examples of welding from the Bronze Age and the Iron Age. From that time the process of welding gone through several modifications, world wars caused a major surge in the use of welding processes, with the various military powers attempting to determine which of the several new welding processes would be best. Many sophisticated welding methods for different alloys of variety applications are available now. Wang D. & Liu S. [1] studied the Friction stir welding of aluminum: In this, the Aluminum plates were friction stir welded at various rotation speeds (850 – 1860 rpm) and travel rates of 30 to 160 mm/min with welding forces ranging from 2.5 to 10 MPa using different dimension welding heads. From the experiments it has found that dimensions of the welding head are critical to produce sound weld. 10% higher micro-hardness is obtained than the parent metal. Scialpi A., et al. [2] studied the influence of shoulder geometry on microstructure and mechanical properties of friction stir welded 6082 aluminum alloy: In this work, the tool analysis has been carried out on AA 6082 T6 1.5 mm thick sheets and the welding process was carried out rotating the tool at 1810 rpm and at a feed rate of 460 mm/min. Three types of shoulder geometries have been taken into consideration. From the experiments it was concluded that TFC tool (tool with fillet and cavity) crown is the best in terms of crown quality. Fujii H., et al. [3] studied the effect of tool shape of friction stir welded aluminum alloys. Boz M. & Kurt A. [4] studied the influence of Stirrer Geometry on Bonding and Mechanical Properties in friction stir welding process: In this, the effect of stirrer geometry on the weldability and mechanical properties of welded aluminum plates using FSW process was investigated. Cabibbo M., et al. [5] studied the microstructure and mechanical property studies of AA6056 friction stir welded plates: In this work, the author has investigated the microstructure and mechanical properties of a friction stir welded 6056- T6 aluminum alloy plate by using polarized optical and transmission electron microscopy techniques. Sarsilmaz F. & Caydas U. [6] studied the statistical Analysis on Mechanical Properties of Friction Stir Welded AA1050/AA5083 couples: In this, the effect of friction stir welding parameters on the mechanical properties of Aluminum alloys as investigated. Sakthivel T., et. al. [7] studied the effect of Welding Speed on Mechanical Properties of Friction-stir Welded Aluminum: In this present investigation aluminum welds were made at various welding speed using the friction stir welding technique by using a hardened steel FSW tool. Adamowski J. & Szkodo M. [8] studied the friction-stir-welds (FSW) of Aluminum alloy AW6082-T6: In this paper the properties and micro-structural changes in friction stir welds in the aluminum alloy 6082-T6 in function of varying process parameters have been investigated. Softening of the material in the weld nugget and heat affected zone was observed i.e. the hardness of both the heat affected zone and the weld nugget is lower than that of the base metal. Rodrigues D. M., et al. [9] studied the influence of Friction Stir Welding Parameters on the Micro- structural and Mechanical properties of AA 6016-T4 Thin Welds: In this present work friction stir welds produced in 1 mm thick plates of AA6016-T4