Microstructure Evolution and Mechanical Properties of Nano-structured Al-0.2 wt%Zr Alloy Fabricated by Accumulative Roll Bonding (ARB) Process

An Al-0.2 wt%Zr alloy was subjected to an accumulative roll bonding (ARB) process up to a strain of 8.0. The process led to ultrafine-grained materials with a mean grain size of 400 nm by 10-cycle ARB process, which was studied by atomic force microscopy (AFM). The Vickers microhardness measurements showed that the hardness value monotonously increased the number of ARB cycles and then reached a constant value of about 45 HV. Yield strength and tensile strength increased during the ARB process and reached to 125 and 158 MPa, respectively, after 10-cycles ARB process. The total elongation and uniform elongation were 65 and 48% before the ARB process and decreased after 10-cycle ARB to 17.5 and 6.5%, respectively. Also, after the tensile test, the fracture surfaces were studied by scanning electron microscope (SEM) and the result showed that the fracture mode in the 0 cycle (before ARB) and 1 cycle was ductile and changed to brittle with further ARB processing from 3 up to 10 cycles.