Effects of Nb addition on the properties and microstructure of Cu-Ni-Si-Mg alloy

Abstract

In this paper, the effects of Nb addition on the mechanical properties, electrical conductivity and microstructure of the Cu-Ni-Si-Mg alloy were investigated. The results show that, after the secondary aging at 460 °C for 120 min, the alloy with 0.2 wt% Nb exhibits the best comprehensive properties with a hardness of 245.9 HV, a tensile strength of 747.28 MPa, a breaking elongation of 8.6%, and an electrical conductivity of 47.74 %IACS. The addition of Nb element can promote the precipitation of Ni 2 Si phase. The Nb-doped alloy has a higher quantity of precipitates and a smaller size of precipitates. The Nb element promotes the transition of the Ni 2 Si phase from a coherent to an incoherent relationship with the matrix in the Cu-Ni-Si-Mg alloy. In the initial stage of precipitation, the precipitation activation energy of the alloy with 0.2 wt% Nb is 46.86% lower than that of the alloy without Nb. The addition of Nb increases the proportion of Σ3 n ( n = 1, 2, 3) grain boundary in the Cu-Ni-Si-Mg alloy. Furthermore, after the secondary aging, the Nb addition increases the recrystallized texture and recrystallized grains and decreases the cold-rolled texture and defects in the alloy. • The Nb addition improves the mechanical properties and conductivity of CuNiSiMg alloy. • The Nb addition promotes the Ni 2 Si phase from coherent to incoherent relationship. • The alloy with 0.2 wt% Nb reduces the precipitation activation energy by 46.86%. • The CuNiSiMgNb alloy has more Σ3 n ( n = 1, 2, 3) CSL boundaries.