Enhancing ductility and post-aging strength of tailor welded blanks through pre-aging friction stir welding

Achieving superior ductility, microstructure, and strength simultaneously in tailor-welded blanks remains challenging. To address this, pre-aging blanks before friction stir welding was proposed. Systematic studies were conducted on the microstructure, ductility, and post-aging strength of pre-aged 2219 aluminium alloy after friction stir welding. Uniaxial tensile tests evaluated the ductility of tailor-welded blanks at room and cryogenic temperatures, along with their mechanical properties after artificial aging. Microstructural characterization and Vickers hardness measurements elucidated the strengthening mechanisms between the welded region and base material. No abnormal grain growth was observed in the welded region post pre-aging welding; instead, a finer grain structure prevailed. Ductility of the tailor-welded blanks initially increased and then decreased with increasing rotational speed. Excellent elongations, 27.8% at room temperature and 32.4% at cryogenic temperatures, were obtained at a rotational speed of 1300 rpm, reaching 91.5% of the base material. This attributed to the finer grain boundary strengthening in the welded regions. After artificial aging, a joint efficiency of 93.5% was achieved, owing to effective compensation of the reduction in precipitation strengthening caused by the welded heat input through finer grain strengthening. This approach represents a novel method for preparing ultrawide blanks for forming integral large-sized aluminum alloy components.