Microstructural evolution and mechanical properties of rapidly solidified thin-strip continuous cast AA5182 Al-Mg alloy under varying heat inputs in friction stir welding

Rapidly solidified thin-strip (TS) continuous cast AA5182 Al-Mg alloy was welded for the first time by the friction stir welding (FSW) technique. The response of solute supersaturation that formed during TS casting to thermomechanical processing during FSW was investigated. The analysis demonstrated that the re-precipitation of the intergranular β-Al₃Mg₂ was strongly affected by weld heat input. Similarly, the microstructural evolution associated with FSW significantly impacted mechanical behavior. It was observed that heat generation results in the formation of a high volume of β-Al₃Mg₂ intermetallic particles and tunneling defects at the advancing side of the stir zones, as well as grain coarsening. Mitigation of solute supersaturation in the stir zone, linked to excess β-phase evolution and consequently solute depletion in the aluminum matrix, was manifested as the simultaneous work-hardening and ductility decline as well as in the stress drop of inhomogeneous plastic flow observed in the tensile specimens.