Abstract: This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding (HRB) based on friction stir welding. The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum, and the tensile specimens fractured at the matrix after exceeding 1 Pa. Non-equilibrium grain boundaries were formed at the hot-rolled interface, and a large amount of Mg₂Si particles were linearly precipitated along the interfacial grain boundaries (IGBs). During subsequent heat treatment, Mg₂Si particles dissolved back into the matrix, and Al₂O₃ film remaining at the interface eventually evolved into MgO. In addition, the local IGBs underwent staged elimination during HRB, which facilitated the interface healing due to the fusion of grains at the interface. This process was achieved by the dissociation, emission, and annihilation of dislocations on the IGBs.