Annealing Behavior of Accumulative Roll Bonding Processed Aluminum Composites

Accumulative roll bonding (ARB) is an effective method to produce ultrafine-grained (UFG) sheet materials with high strength. In this work, the ARB process up to five cycles was performed to the starting materials AA1050 and AA6061 and produced three different laminates: AA1050/AA1050, AA6061/AA6061, and AA1050/AA6061. The grain size of AA1050 and AA6061, in all laminates, was reduced significantly after ARB deformation. Meanwhile, a remarkable enhancement in the hardness was achieved. The materials were annealed at different conditions and the microstructures and mechanical properties of the materials were investigated. Static annealing was carried out at temperatures of 100-400 degrees C for 30 min in order to examine the thermal stability of the aluminum alloy. The grain size and hardness evolution of both the AA1050 and AA6061 alloys, in all the three laminates, showed a similar change with the annealing temperature. Annealing induced hardening was observed at 100 degrees C for all the materials examined, and the microstructure of the alloys stayed almost the same as the as-deformed alloys. The materials softening started after annealing at 150 degrees C, and the hardness decreased rapidly between 150 and 300 degrees C and then stayed stable. The change of the hardness values with the annealing time at low temperature was nearly negligible. The hardness and grain size values of the AA1050 and AA6061 in both the monotonic laminates and composite are similar.