Effect of the composition and production process parameters on the microstructure, residual stresses, and mechanical and corrosion properties of gold alloys used in industrial jewelry processes

Abstract

Gold alloys, used in the production of both hollow and solid gold chains, influence the optical and mechanical properties of various gold products. Also, the microstructure of the alloys strongly influences the mechanical properties, which have a key role in both the machinability and quality of the plates. In the present work, different compositions of gold alloys and various industrial deformation processes (annealing and rolling steps) were analyzed and optimized. The change in the production parameters and in the compositions of the alloys may lead to the formation of different levels of residual stresses within the material, which can generate a variation in the behavior of gold sheets. The microstructures after the different production processes were analyzed by OM and SEM observations, whereas the variation of mechanical properties by microhardness tests. The residual stresses were evaluated using XRD analysis and the corrosion resistance by potentiodynamic polarization tests. The results showed that with the optimized process, a higher homogeneity of the microstructure, with an increase of the quality of semi-finished products and without ruptures under roller trains, was obtained. Moreover, the grain refiner was changed and a totally non-magnetic gold alloy was developed. Finally, to improve the weldability of the final chains, a different gold welding alloy, with a lower melting point, was developed and optimized.