AN EXPERIMENTAL STUDY ON FRICTION STIR WELDING OF ALUMINUM- MAGNESIUM ALLOYS FOR IMPROVED MECHANICAL PROPERTIES OF TAILOR WELDED BLANKS

Tailor welded blanks (TWB) are used in automotive and aerospace industries as they offer weight saving followed by cost saving and improved fuel economy. Being light in weight and having low cost, Aluminum alloys have piqued the interest of scientists. Friction Stir Welding (FSW) is a well-known accepted technique used since 1991 worldwide for Aluminum and its alloys. Due to friction stir welding, mechanical changes occur due to stirring action at the joint. Also the inter-metallic compounds, kissing bond formation, onion ring formation etc. are defects encountered in the nugget zone of welding. Hence, a novel technique is suggested to carry out the friction stir welding using a blend of techniques viz. double sided friction stir welding and multi objective optimization of process parameters. For experimentation, AA 5182 and AA 5754-Aluminum Magnesium alloys of 5000 series are used with sheet size of 1.5 mm thickness. Experimentation was carried out on a vertical machining center, with circular, square, and triangular tool pin profiles with a tool rotational speed range between 1500-1800 rpm and a welding speed range of 40 mm/min.-60 mm/min. For the analysis purpose, L9 orthogonal array was used and Grey Relational Analysis(GRA) was employed and ASTM standards were used for tensile testing. Base sample materials of AA 5182 and AA5754 are having ultimate tensile strengths of 289.58 N/mm2 and 220.75N/mm2respectively. The designed welded blank of the two materials recorded maximum ultimate tensile strength of 268.11N/mm2which was remarkable for FSW. Welded joint efficiency was found to be 92.73% and percentage elongation of TWB was found to be 44% as compared to the base metals.