Enhancing co-deformation ability of nanograined Ni-W layers in the Ni/Ni-W laminated composites

Abstract

Tensile properties and plastic deformation behavior of the Ni/Ni-W laminated composites with different thickness ratios of the Ni layer to the Ni-W layer were investigated systematically. Experimental results reveal that the strength/ductility synergy of Ni/Ni-W laminated composites with a large thickness ratio is improved compared with that of monolithic Ni, which is attributed to the enhanced co-deformation ability of the nanograined Ni-W layers with decreasing the Ni-W layer thickness. Ni-W layers with small original layer thickness achieve continuous thinning through the stable grain boundary sliding under the interface constraint. Furthermore, there is an evident transition of the fracture behavior from the co-existence of channel cracks and micro shear bands to micro shear bands for the Ni-W layers with decreasing the Ni-W layer thickness. Finite element simulations show that the decrease of the Ni-W layer thickness leads to the decrease in the sensitivity of the composites to defects, which is corresponding to the reduced stress concentration degree at the crack tip. Based on the energy criterion, the plastic deformation map controlled by the length scale and the flow stress for the Ni-W layers was evaluated. The finding may provide a potential strategy for the design and development of high-performance materials for high-temperature microelectromechanical systems.