Research on microstructural evolution, hardness, and electromagnetic shielding capabilities of Ni/Cu multilayered composites

The low-speed accumulative roll bonding (ARB) process is an effective way to achieve metal-based composites with ultra-fine-grained layers. In the current study, the effect of ARB pass and the number of layers in composite stacking were studied in Ni-based and Cu-based composites. According to the findings, by increasing the ARB pass, the reinforcing layers were broken and distributed in the matrix. Also, the size of grains in Ni and Cu layers decreased. On the contrary, the hardness of Ni and Cu layers increased. Comparing pass 1 and pass 7 showed that there were 105 HV and 24 HV growth in hardness of Ni and Cu, respectively. Furthermore, the hardness profile of layers showed the highest growth near composite surfaces and interfaces. The variations of hardness values showed fluctuations after ARB pass 7. Additionally, the shielding efficiency increased due to the increased number of Ni/Cu interfacial barriers. The maximum values of EMI shielding were 55 dB in Ni-based composites and 59 dB in Cu-based composites, respectively. However, by increasing the layers in composite stacking, better distribution of reinforcing layers in the matrix and higher shielding efficiency were obtained while less grain refinement and less hardness growth were observed. The maximum EMI shielding values were seen in Ni/Cu/Ni/Cu/Ni/Cu/Ni and Cu/Ni/Cu/Ni/Cu/Ni/Cu composites while the highest hardness growth was seen in Ni/Cu/Ni and Cu/Ni/Cu composites.