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).
