Effect of microstructure and residual stresses, generated from different annealing and deformation processes, on the corrosion and mechanical properties of gold welding alloy wires

Abstract

Gold welding alloys, which are used in the production of both hollow and solid gold chains, affect the optical and mechanical properties of various gold products because the corrosion resistance of the individual links depends on these properties. It is important that welding alloys with high corrosion resistance do not degrade during or after the production process. The mechanical properties of gold welding alloy wires are strongly influenced by the alloy microstructure, which has a key role in both the machinability and the quality of the wires. In the presented work, various physical and mechanical properties of gold originating from different industrial deformation processes are evaluated. Specifically, various plastic deformation grades caused by different annealing and rolling steps are analyzed. The change of the temperature, time, and velocity parameters in the annealing and lamination processes leads to the formation of different levels of residual stresses in the material, which can generate a variation in the corrosion properties of the gold wires. The change in microstructure, due to the different annealing and rolling steps, is analyzed by optical microscope (OM) and SEM observations. The residual stresses are evaluated using XRD analysis, and the variations of the mechanical properties by micro-hardness tests. The corrosion resistance is evaluated by potentiodynamic polarization tests, in which an electrolyte solution is used to simulate human sweat. Small grain size and high homogeneity of the microstructure are preferred for the final products. In this study, the samples that have been produced are shown to have lower levels of residual stresses and feature higher corrosion resistance and more favorable mechanical properties.