Effect of Brushing Direction and Annealing on the Microstructure and Bonding Strength of AA6061 Aluminum Alloy Processed by Accumulative Roll-Bonding

Accumulative Roll-Bonding (ARB) process is a Severe Plastic Deformation (SPD) process run to produce Ultra-Fine Grained (UFG) sheets using intense plastic strains via rolling machine. In this research, the effect of surface condition (brushing) and annealing treatment on the fracture surface and bonding strength of the ARBed AA6061 sheets was investigated. In this regard, the specimen surfaces were first brushed in three different directions, i.e., Rolling Direction (RD), Transverse Direction (TD), and both RD and TD. The ARB process was conducted up to five cycles, and specimens were tested after the first, third, and fifth cycles. The annealing treatment was conducted for two hours at 415 °C after the first, third, and fifth cycles. The bonding strength and hardness profile in the cross-section (perpendicular to the rolling direction) were measured through peeling and hardness tests, respectively. The results show that RD is the most effective direction for brushing to achieve high bonding strength with the mean strength of 0.60 N/mm. The fracture surfaces of the specimen were observed using a Scanning Electron Microscope (SEM). The results represent the broad areas of mechanical bonding in the rolling direction. Further, post-annealing treatments are shown to increase the bonding strength