Au-25Cu-25Ni-25Pd medium-entropy alloy with high strength and low electrical resistivity

A new non-equiatomic Au-25Cu-25Ni-25Pd (wt%) medium-entropy alloy was designed and prepared. Firstly, the phase transformation, microstructures and mechanical properties during ageing were investigated. The Au-25Cu-25Ni-25Pd MEA exhibited excellent working property with cold deformation of 90%, and cold deformation can largely improve the hardness which presented work hardening effect. After ageing at 450–650 °C for 1 h, phase decomposition was experimentally detected, producing Ni-rich and Cu-rich phases both with FCC structure, and the microstructure of phase decomposition showed lamellar structures. Meanwhile, spinodal structure, L10 and short-range ordered structures with 1/2{311} reflections formed in the alloy. The hardness and ultimate tensile strength of the samples deformed and then aged at 450 °C for 1 h can reach 449 HV and 1389 MPa, respectively. Moreover, the alloy has a low electrical resistivity after low-temperature ageing. Spinodal structure and ordering structures can strengthen the alloy and decrease the electrical resistivity simultaneously. This study paves the way for less-noble-metal medium-entropy electrical contact alloys.