Simultaneously enhancing mechanical and bonding property of Cu-Ni-Si/1010 steel bimetal laminated composites via annealing

Abstract

Annealing is an effective method for improving mechanical properties of bimetallic laminated composites (BLCs). The temperatures of 400 °C, 450 °C, 500 °C, and 550 °C were selected to investigate microstructure evolution and mechanical behaviors of Cu-Ni-Si/1010 steel BLC. Microstructure analysis shows that the size and volume fraction of nano-strengthening δ-Ni₂Si phase increase with temperature in Cu-Ni-Si. Annealing ameliorates the elemental enrichment at the interface by promoting the diffusion of Ni and Si elements into 1010 steel. The uniaxial tensile results indicate that yield strength, ultimate tensile strength, and elongation of BLCs increase first and then decrease with increasing annealing temperature. The strength improvement is attributed to the enhanced precipitation strengthening of Cu-Ni-Si and heterogeneous deformation-induced strengthening, and the ductility improvement results from the increased plastic deformation ability of 1010 steel. Tensile shear test indicates that fracture occurs at the Cu-Ni-Si side when the annealing temperature is below 450 °C, and when the temperature is higher than 500 °C the interface begins to debond. The thickening of the diffusion layer and the strengthening of Cu-Ni-Si with increasing temperature enhance the shear strength, however, excessively high temperatures lead to the formation of interfacial voids, resulting in the weakening bonding strength. Overall, the BLC after annealing at 450 °C exhibits the excellent mechanical performance. This study provides a new approach for enhancing the strength and plasticity of BLCs that are not suitable for deformation.