Manufacturing of high-strength multilayered composite by accumulative roll bonding

Abstract

In this study, high strength Al/Mg composite was produced using Al 5052 and Mg AZ31B by applying three passes of the accumulative roll bonding (ARB) process at room temperature. For this purpose, microstructure, plastic instability, and mechanical properties were assessed by optical microscopy, x-ray diffraction (XRD), uniaxial tensile test, and Vickers microhardness. The microstructure showed that by rising the exerted strain, grains were drawn in the rolling direction and grain refinement in Mg layers occurred. The crystallite size for Al after first and second ARB passes reached 192 nm and 173 nm, respectively. The lamellar structure was also maintained after the second pass; however, necking, fracture, and waveform formation in Mg layers were quite visible. The results of mechanical properties showed that by increasing the number of ARB passes, the values of UTS and microhardness for both Al and Mg layers increased sharply at the zero pass and gradually at first and second ARB passes, respectively. Also, the maximum UTS reached 475 MPa, which was at least a 100% improvement compared to previous researches. Variation of microstructure and mechanical properties during ARB process are related to many factors such as severe plastic deformation, locking of dislocations, continuous recrystallization, lamellar structure and two mechanisms of work hardening and grain refinement at initial and last ARB cycles play a central role.