Effects of silicon and thermo-mechanical process on microstructure and properties of Cu–10Ni–3Al–0.8Si alloy

• Cu–10Ni–3Al–0.8Si alloy with ultra-high strength was designed.
• The addition of silicon hindered the precipitation of large NiAl phase.
• Tensile strength and electrical conductivity were 1180 MPa and 18.1% IACS.
• Nano-scale Ni2Si and Ni3Al improved the strength and electrical conductivity.

Cu–10Ni–3Al–0.8Si alloy with ultra-high strength was designed and its microstructure was studied using optical microscopy, scanning electron microscopy, transmission electron microscopy. The alloy went through a set of thermo-mechanical process: solution treated at 950 °C for 4 h, then cold-rolled by 50% and aged at 450 °C for 8 h, followed by 60% cold-rolling and aging at 450 °C for 8 h. After these treatment, the tensile strength was 1180 MPa, yield strength was 1133 MPa and electrical conductivity was 18.1% IACS, respectively. The comprehensive properties, especially the electrical conductivity of the designed alloy, were much higher than those of traditional Cu–Ni–Al alloys. The addition of silicon in the designed alloy hindered the precipitation of large-scale NiAl phase and improved the strength of the alloy. The orientation relationships between δ-Ni2Si, Ni3Al precipitates and copper matrix were: [001]Cu‖[001]Ni3Al‖[001]δ,(110)Cu‖(110)Ni3Al‖(010)δ,(11¯0)Cu‖(11¯0)Ni3Al||(100)δ, respectively.