Influence of solution-hardening on the mechanical properties and wear resistance of copper alloys

Abstract

Solid-solution hardening can increase the wear resistance of metals, involving two factors: the solute 1) pins dislocations, leading to increased hardness of the metals; 2) influences the atomic bond strength and thus Young's modulus, which also affects the resistance to dislocation generation and movement. Solute atoms generally increase hardness of the host metal but may increase or decrease its Young's modulus, which is related to the solute's electron work function (EWF). In this study, Cu (EWF = 4.65 eV) was hardened by solutes, Ni (EWF = 5.15 eV), and Mn (EWF = 4.1 eV), respectively. CuNi (10, 30, 60, 80 wt% Ni) and CuMn (2, 4, 6, 8 wt% Mn) alloys were prepared using an arc furnace. It is demonstrated that with Ni addition, both hardness and Young's modulus increased, while Mn addition led to a decrease in Young's modulus though the hardness was increased. As a result, the effect of Ni on the wear resistance of Cu is underestimated when predicted using the classic Archard equation, while that of Mn is overestimated. Such an issue of under- or over-estimation can be corrected using a wearing energy model, which takes into account the influence of Young's modulus on the wear resistance. The wearing energy model is a modified form of Archard equation, established by including wearing energy consumption via the relationships among atomic bond strength, Young's modulus, and EWF. Density functional theory (DFT) calculations on CuMn and CuNi alloys systems confirm a stronger metallic bond in CuNi with higher overall EWF, compared with that in CuMn showing a lower overall EWF.