Evaluation of mechanical properties and microstructure for Al/Ni %5 produced by cross accumulative roll bonding process

In recent years, different SPD methods have been attention of researchers to produce metal matrix multi-layered composite and to achieve good mechanical properties and microstructure. Among SPD methods, CARB process is inspired by ARB which has the ability to produce metal composites with better mechanical and microstructural properties. In this investigation, for the first time, aluminum composite matrix consisting of 5% pure nickel powder was produced by CARB in eight pass. Microstructure and mechanical properties of produced composite were evaluated in the different cycles of CARB process by optic and scanning electron microscopy, elemental analysis, uni-axial tensile test, microhardness, respectively. Results of microstructure showed that the bonding between the layers in the first passes is weak and there is a porosity in structure but by increasing the passes and after 8 pass, in produced composite, distribution of nickel powders and oxide layers has better than previous cycles, and porosity reduced. By increasing the number of CARB passes, tensile strength and microhardness increased continuously. The reason for this increase is due to the governing mechanisms in the process of SPD, and the nickel powder did not contribute much to this increase. Also, the amount of elongation after a severe drop in the initial sandwich, increased by increasing the pass until the end of the eighth cycle, continuously with a low increase rate. The tensile strength and microhardness increased 3.88 and 2.5 times, respectively, compared to the annealed sample