EXPERIMENTAL INVESTIGATION USING BEST TOOL PARAMETERS ON MICRO FRICTION STIR WELDING OF DISSIMILAR ALLOYS (Al6061-Al5251)

Abstract

A term micro friction stir welding is introduced when dealing with joining of base materials having thickness less than 2mm. This study investigates the effect of square shaped pin profile and welding parameters with mild steel as fixture back plate material on the welded joints formed with dissimilar alloys. Using AA 6061-O and AA 5251-H22 base material of different thicknesses, three different welding parameters namely rotational speed, traverse speed and coupons position have been taken into consideration. The welding joint is created in square butt joint configuration at rotational speed 1675 rpm, 2850 rpm and traverse speed at 60 mm/min and 80 mm/min by keeping the rotation of tool anti clockwise throughout the experiment. Both mechanical testing i.e. tensile and hardness etc. and microstructure analysis have been performed after T-6 thermal treatment to tensile samples. The results showed that the optimal parameters are 2850 rpm and 60 mm/min on which maximum tensile strength recorded as 104 MPa when 5251-H22 is at advancing side whereas highest average micro hardness value recorded in NZ is 84.41HV. In NZ micro hardness trend increased by increasing rotational speed and decreased by increasing traverse speed for both advancing side (AS) and retreating side (RS). However, micro-hardness of NZ is found greater than the hardness of base material (6061-O & 5251-H22).