Forming Quality and Microstructure Evolution of AA6061‐T6 Aluminum Alloy Joint during Flow Drill Screwing Process

Abstract

Flow drill screwing (FDS) is the optimal process to realize the single‐side connection of metal sheets. However, the plastic deformation and high fractional temperature during the plate connection process significantly impact the mechanical properties and microstructure of the metal sheets. Herein, the AA6061‐T6 sheet is connected by the FDS process, and the forming quality and microstructure evolution of the alloy are studied. The results show that the plate and the screw are mechanically connected. Obvious plastic deformation and recrystallization occur in the aluminum alloy around the screw, resulting in a fine‐grained zone near the joint interface. The recrystallization phenomenon in the central bushing region promotes the intermolecular fusion between the plates. The high temperature in the connection process partially promotes the dissolution of the strengthening phase, resulting in a decreased strength of the alloy matrix near the screw. The softening zone and hardening zone appear in the plates after the connection, and the hardness values are 55.8% and 105.7% of the alloy matrix.