Effect of Co Addition on Microstructure and Properties of Cu-Ni-Si Alloy

Cu-Ni-Si system alloys have been the research hotspots because of high strength and high electrical conductivity in recent years. In this study, the influence of Co addition on microstructure and properties of Cu-Ni-Si alloys were investigated by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The result shows that the hardness of alloys increase firstly, gradually decline and leveled off while reaching a certain peak with the prolongation of aging time, which the electrical conductivity gradually increased. The best integrated performance is obtained at 500 degrees C aging for 4 h, which reaches the peak value of 233 HV and the conductivity was 37.3% IACS, the ultimate and yield strength reached 583 and 496 MPa, At the same time, the ductility of Cu-Ni-Si-Co alloy reached 12.9%. The phases of (Ni, Co)(2)Si precipitated with the addition of Co, which strengthens the alloy and enhances the mechanical properties. However, the formation of Co2Si phase leads to Ni element dissolved in the matrix, which gives rise to the reduction of conductivity.