Characteristics of Ultra-Fine Grained Al/Cu/Sn/Ni Multi-Layered Composite Produced Byaccumulative-Roll-Bonding (Arb) Process

The aim of the present study is to investigate the microstructure and mechanical properties of the Al/Cu/Sn/Ni multi-layered composite (MLC) processed by accumulative roll bonding (ARB) at room temperature over seventh cycle. Microstructural results by scanning electron microscopy show that the fracture of the nickel and the copper layers occurred in the first and third cycles of the ARB process, respectively. But the tin layer has remained without fracture up to the seventh cycle. In addition, the TEM images clearly show that during the third cycle of the ARB process, the occurrence of dynamic recovery (DRV) phenomenon and formation of sub-grain in the aluminum matrix of the MLC structure have occurred quite well. Furthermore, as the strain increases during the seventh cycle of the ARB process, the severe dynamic recrystallization (DRX) phenomenon has occurred in the aluminum matrix microstructure of the Al/Cu/Sn/Ni MLC. STEM images show that the grain size of the aluminum matrix during the seventh cycle has also been reached approximately below 350 nm. Tensile strength of the Al/Cu/Sn/Ni MLC during the seventh cycle of the ARB process was reached its maximum value (188 MPa), but the elongation of the Al/Cu/Sn/Ni MLC was decreased compared to the initial cycles and reached 6.5%. Also, with increasing the number of the ARB cycles, the hardness of the matrix and reinforcement layers has steadily been increased. The fracture surface of aluminum and copper layers during the initial cycles of the ARB process was ductile. But, with developing the ARB process, the fracture surface of these layers has been undergone brittleness. Besides, the fracture surface of nickel and tin layers has been brittle in all stages