Experimental evaluation of forming limit diagram and mechanical properties of nano/ultra-fine grained aluminum strips fabricated by accumulative roll bonding

In this research, for the first time, forming limit diagrams (FLDs) of ultra-fine grained Al/Al samples produced by accumulative roll bonding (ARB) process were evaluated. The samples were successfully prepared through ARB up to the 7th pass. Mechanical properties, tensile fracture surfaces, and crystallite size of samples were investigated. The level of the FLD and elongation at first decreased and then increased, continuously. The results of tensile testing revealed that by increasing the number of ARB passes, the tensile strength increased continuously. Microhardness of Al strips increased and reached a value of 51 VHN after the seventh pass. Results of X-ray diffraction demonstrated that crystallite size decreased from 1 341 nm for annealed condition and it reached to 175 nm for ARBed samples after the 7th pass. SEM images showed that the fracture mode in the ARBed samples was a shear ductile fracture with elongated sophomoric shear dimples