Tuning tribological, mechanical and electrical properties of Ag-X (X=Al, In, Sn) alloys

Abstract A new design concept for silver based alloys with a hexagonal structure as electrical contact materials with enhanced tribological properties has been investigated. The correlations between the phase composition and the tribological properties have been investigated in the Ag-Al, Ag-In and Ag-Sn systems. In each system, alloys with different chemical compositions were prepared by melting in evacuated ampoules. Characterisation techniques such as: optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopies (SEM and TEM) have been used to evaluate the microhardness, tribological properties and contact resistance of the samples. The phase compositions of the synthesized Ag-Al and Ag-Sn alloys were in agreement with the phase diagrams and the metastable hcp phase was observed in the Ag-In system. The friction coefficients and wear rates of all the hcp-Ag-X (X = Al, In, Sn) alloys were considerably lower than pure Ag or fcc-Ag alloys. This is attributed mainly to easily shearing basal planes in the hcp structure. The Ag-Sn alloys showed high contact resistances, making them less suitable for a sliding electrical contacts. In contrast, the Ag-In alloys showed much lower contact resistance, making them better alternatives for practical applications.