Effect of Cr on the Microstructure and Mechanical Properties of Cu-Ni-Si Alloys

A systematic study was conducted on the influence of Cr on the property evolution and precipitation behavior of Cu-Ni-Si alloys. Results indicate that Cu-Ni-Si alloys containing 0.33 at% Cr exhibit superior mechanical properties after three-stage cryogenic rolling and aging, achieving a tensile strength of up to 862 MPa. The addition of Cr induces competitive precipitation behavior between Cr and Ni for Si. It promotes the precipitation of Cr3Si phases at various scales while suppressing the formation of Ni3Si phases. Concurrently, it enhances the precipitation of fine nanoscale precipitation-hardening phases Ni2Si, optimizing the alloy’s precipitation hardening effect. Furthermore, the addition of Cr suppresses dislocation annihilation. The formation of finer precipitates pins the dislocations introduced during cryogenic rolling and impedes their motion, thereby enhancing the alloy’s strength and hardness. The alternating and staggered distribution of soft and hard microzones in the Cr-containing alloy results in more uniform overall properties of the sample. However, the reduced proportion of soft microzones slightly decreases the alloy’s electrical conductivity.