Multi-Pass Friction Stir Lap Welding of AA 6061-T6: Implication of Tool Pin Overlapping on Microstructure and Mechanical Properties of Joints

The present study focuses on the influence of a 5-pass overlapped friction stir lap welding AA6061-T6 mitigation defects and its simultaneous effect microstructure mechanical properties. Tool pin overlapping percentage 0%, 25%, 50% 75% was employed, from which it observed that significantly reduced at higher overlapping. Fine equiaxed grains were across all nugget zones in both top, bottom regions developed due to passes; grain size varied 8.5 µm 3.5 µm. became finer, increased percentage. microhardness processed zone during range 43 HV0.1 49 as compared base metal interpreted changes secondary precipitate distribution A maximum ultimate tensile strength 230 MPa achieved overlapping, whereas minimum 160 0% Fractography fracture surface showed ductile failure number dimples varying shapes sizes.