Developing aluminium–zinc-based a new alloy for tribological applications

Abstract

In order to develop aluminium–zinc-based a new alloy for tribological applications, six binary Al–Zn and seven ternary Al–25Zn–(1–5)Cu were prepared by permanent mould casting. Their microstructure and mechanical properties were investigated. Dry sliding friction and wear properties of the ternary alloys were investigated using a pin-on-disc machine. Surface and subsurface regions of the wear samples were studied with scanning electron microscopy (SEM). The highest hardness and tensile strength were obtained with the Al–25Zn alloy among the binary ones. The microstructure of this alloy consisted of aluminium-rich α and eutectoid α + η phases. Addition of copper to this alloy resulted in the formation of θ (CuAl2) phase. The hardness of the ternary alloys increased with increasing copper content. The highest tensile and compressive strengths and wear resistance and the lowest friction coefficient were obtained from the ternary Al–25Zn–3Cu alloy. The dimensional change measured on ageing (stabilization) of this alloy was found to be much lower than that obtained from the copper containing zinc-based alloys. Microstructural changes were observed below the surface of the wear samples of the Al–25Zn–3Cu alloy. These changes were related to the heavy deformation of the surface material due to normal and frictional forces, and smearing and oxidation of wear material. Adhesion was found to be the main wear mechanism for the alloys tested.