Orbital friction stir lap welding of AA5456-H321/AA5456-O aluminum alloys under varied parameters

This work aims at studying the effect of triflute pin tools on single-pass orbital friction stir lap welding of AA5456-H321/AA5456-O alloys by varying pin length, tool rotational, and travel speeds. The mechanical properties of welds were examined while the microstructures and fracture modes of welds were observed and analyzed via the aid of an optical microscope, scanning electron microscope, and energy dispersive X-ray spectroscopy. The results show that upward-thrust flow and intermingling of the alloys are directly improved with an increase in tool rotational speed. Strengthening precipitate dissolution (AA5456-H321) and grain size strengthening (AA5456-O) occur in the stir zones. Weld samples without volumetric flow defect/microvoids are obtained as the tool rotational speeds are increased. Optimum weld strength of 303 MPa was obtained at tool rotational and travel speeds of 900 rpm and 45 mm/min, respectively. Fracture location and nature of dimples are influenced by the level of tool rotational speed.