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Mechanical behaviour of friction stir welded AA7075-T651 joints considering the effect of tool geometry and process parameters

ABSTRACT Obtaining high-strength aluminium alloy welded joints considering the effect of tool geometry and process parameters still needs attention. In this study, AA7075-T651 aluminium alloy plates were joined using friction stir welding (FSW). The mechanical behaviour of joints was investigated considering the effect of tool rotation, welding speed, and stirred pins having two different geometries (conical pin and conical threaded pin). The welded joints were characterised by their tensile strength, microhardness, microstructure, and percentage elongation. Welds exhibited superior tensile properties when conical threaded pins were used. The optimised FSW process parameters revealed higher tensile strength of 177 MPa, the microhardness of 136 HV, and surface roughness of 15 μm with the conical threaded pin at tool rotation and welding speed of 1740 rpm and 40 mm/min, respectively. No significant difference in the microhardness was observed with both tools. The highest joint efficiency and percentage elongation of 34% and 17.4% were observed with the conical threaded pin.