Simultaneous enhancement of mechanical properties and electrical conductivity in Cu-Ni-Si alloy by constrained groove pressing and aging treatments

In this work, the Cu-Ni-Si alloy sheets with a thickness of 1.5 mm were prepared by constrained groove pressing (CGP) and aging treatments. The results show that the combination of CGP and aging treatments can simultaneously improve the mechanical properties and electrical conductivity of alloy. The sample subjected to 10 passes of CGP treatment and aged at 460 °C for 1 h exhibits optimal comprehensive properties, with a hardness of 234.8 HV, an ultimate tensile strength of 773.5 MPa, an electrical conductivity of 38.1 %IACS, and a favorable breaking elongation of 15.7 %. Compared to the peak-aged sample without CGP treatment, the hardness, ultimate tensile strength and electrical conductivity increase by 12.4 %, 15.1 % and 5.5 %, respectively. The CGP treatment can refine the grain size of alloy and increase the dislocation density, thereby promoting the precipitation of solute atoms during the aging process. The aged sample subjected to CGP treatment has a higher quantity of δ-Ni₂Si precipitates, and the formation of Ni₃Si₂ precipitates is inhibited. After aging treatment, the proportion of Σ3 grain boundary increases in the sample subjected to CGP treatment. Compared to random grain boundaries, the adjacent grains on both sides of Σ3 grain boundaries have a smaller Schmid factor mismatch, which helps to improve intergranular deformation compatibility. Moreover, the scattering effect of Σ3 grain boundaries on electrons is smaller. Therefore, the higher proportion of Σ3 grain boundary can improve the ductility and electrical conductivity of Cu-Ni-Si alloy.