Abstract:Cu-Ni-Si alloys are commonly used in lead frame, electrical contacts, connectors and other components. However, the traditional preparation process is complex. Vacuum die casting technology provides a new way to produce high-performance copper alloys with a simpler process. In this paper, a Cu-Ni-Si-Co-Zr alloy was prepared using vacuum die casting and the effects of solution aging (SA) and direct aging (DA) on the microstructures and properties were investigated. The results showed that after the SA treatment (solid solution for 1.5 h at 900 ℃ and aging for 7 h at 500 ℃), a large number of massive and netted micron-sized Zr-containing phases and nano-sized acicular phases precipitated in the alloy, contributing to a microhardness of (215.2±3.8) HV, tensile strength of (552.3±16) MPa, and conductivity of (41.9±0.2) %IACS. Notably, after the DA treatment (aging for 6 h at 500 ℃), the alloy grains were refined. The hardness increased to (237.1±4.2) HV, the tensile strength was (632.4±20) MPa, and the conductivity decreased to (33.0±0.3) %IACS. This study discussed the effects of different heat treatment processes on the microstructure and properties of vacuum die casting copper alloys. It provided theoretical guidance and data support for the development of high-performance copper alloys.