Effect of Mg microalloying on the microstructure and properties of conductive Cu-Ni-Al alloy with ultra-high strength

Building upon the high-performance Cu-13.3Ni-6.7Al alloy, we investigated the effects of microalloying with four different Mg concentrations: 0.25 at%, 0.50 at%, 1.00 at%, and 2.00 at% on the microstructure and properties of ultra-high strength, conductive Cu-Ni-Al alloys. Notably, the alloy containing 1.00 at% Mg, after aging treatment at 500°C for 24 hours, exhibited superior comprehensive properties. The ultimate tensile strength and electrical conductivity reached 1092 MPa and 16.4 %IACS, respectively, representing an 8.3 % increase in tensile strength and a 2.5 % increase in electrical conductivity compared to the Cu-13.3Ni-6.7Al alloy. At this optimal concentration, the grain size of the alloy was reduced from 1.5 μm to 1.3 μm, the precipitate size decreased from 9.9 nm to 9.0 nm, and the volume fraction of precipitates increased from 8.0 % to 8.8 %. These changes resulted in grain boundary strengthening, dislocation strengthening, and precipitation strengthening effects of 125 MPa, 155 MPa, and 690 MPa, respectively. The addition of Mg effectively lowered the interfacial energy of Ni ₃Al precipitates, thereby enhancing the nucleation rate of the precipitates and subsequently improving the alloy`s overall mechanical and electrical properties. This study provides valuable insights into the appropriate alloying elements for designing high-performance Cu-Ni-Al alloys.