Characteristics of thin Al/steel/Al sandwich produced via accumulative roll bonding technique for electromagnetic shielding applications

Tri-layered Al/steel/Al composites with 0.2 mm thickness were produced by accumulative roll bonding (ARB) process at room temperature using Al-1050 sheets and a commercial low carbon steel DC01 up to four cycles. The effect of ARB cycles on the microstructure, mechanical properties and magnetic shielding of the ARBed sandwiches is investigated. The microstructural results obtained using SEM and EBSD techniques showed that the steel layers were necked and fractured as the strain increases and a small part of steel fragments was observed in some points of Al matrix. Further, the outer Al layers tend to disappear and to be replaced by steel layers, which may be due to the softening of the Al alloy resulting from the intermediate annealing performed at 400°C for 10 min between each ARB cycle. During ARB cycles a pronounced decrease of the grain size is observed in Al layers and the HAGB of both Al and steel layers showed a little increase with respect to primary sandwiches. The tensile tests revealed a significant reduce in tensile properties of the sandwich after 2 passes due to the fragmentation of steel inside the Al matrix. The shielding effectiveness (SE) of multi-layered Al/steel/Al composites is evaluated from 20 Hz to 20 KHz versus the cycle number. The SE of ARB processed sandwich showed a similar behavior as steel shielding at low frequency and gradually increases with increasing frequency.