Microstructure and mechanical properties of ultra-fine grains (UFGs) aluminum strips produced by ARB process

Accumulative roll-bonding (ARB) process is a severe plastic deformation process capable of developing grains below 1 μm in diameter and to improve mechanical properties. In this study, strips of a commercial pure aluminum were ARB-processed to eight cycles, and their microstructures and mechanical properties were investigated. XRD and TEM studies of the strips showed grain refinement, and the TEM micrograph of the alloy ARBed for eight cycles showed ultra-fine grains (UFGs) of high-angle grain boundaries ∼360 nm in size. The ambient tensile strength and microhardness of the ARB-processed samples increased with the number of ARB cycles. Whereas, the elongation dropped abruptly at the first cycles, above which it remained nearly constant. With increasing ARB process, the bending strength increased and sliding wear resistance decreased. SEM fractography of fractured surfaces after tensile tests revealed that failure mode in ARB-processed aluminum was shear ductile rupture with elongated small dimples.