Abnormal rapidly homogenized joining of aluminum alloys through a cross-scale diffusion

Rapidly homogenized joining has been a longstanding pursuit in the forming manufacturing of lightweight alloys structures. In this study, ultrasound energy was introduced into the joining process to accelerate cross-scale diffusion (direct grain migration rather than atomic-scale diffusion), and a homogeneous 6063Al joint was fabricated using a Zn-40Sn alloy at 360 °C in air. The network architecture joint composed entirely of α-Al grains was formed with a sandwich structure consisting of Sn@Al₂O₃/MgO as the grain boundary. The tensile strength of the joints was higher than that of the base metal in only a very short diffusion time (180 s). Physical effects of ultrasound in the Sn-Zn molten metal induced violent intergranular penetration, resulting in the decohesion and migration of the α-Al grains from the base metals and realizing a rapidly homogenized joining. This provides a foundation for full-strength joining of high-strength aluminum alloys with low thermal damage.