Change In Microstructure and Mechanical Properties Of Four-Layer Stack ARB Processed Complex Aluminum Sheet with Annealing

The four-layer stack accumulative roll bonding (ARB) process using AA1050, AA5052 and AA6061 alloy sheets is performed up to 2 cycles without a lubricant at room temperature. The sample fabricated by the ARB is a multi-layer complex aluminum alloy sheet in which the AA1050, AA5052 and AA6061 alloys are alternately stacked to each other. The changes of microstructure and mechanical properties with annealing for the-ARBed aluminum sheet are investigated in detail. The as-ARBed sheet shows an ultrafine grained structure, however the grain diameter is some different depending on the kind of aluminum alloys. The complex aluminum alloy still shows ultrafine structure up to annealing temperature of 250℃, but above 275℃ it exhibits a heterogeneous structure containing both the ultrafine grains and the coarse grains due to an occurrence of discontinuous recrystallization. This change in microstructure with annealing also has an effect on the change of the mechanical properties of the sample. Especially, the specimen annealed at 300℃ represents abnormal values for the strength coefficient K and work hardening exponent n value.