Investigation of Supersaturated Silver Alloys for High Hardness Jewelry Application

Sterling silver is one of the most widely used precious metal alloys in jewelry industry. 92.5 wt% silver content is the standard for sterling products, while 7.5 wt% is reserved for other alloying elements. Because the mechanical properties of pure silver such as yield strength and hardness are extremely low. In the bounds of 7.5 wt% solute addition, different approaches have been introduced in order to improve the properties of sterling silver. For example, to increase the hardness of the jewelry pieces, metallurgists introduced age hardening, cold working, and surface treatments. We reported on the trend of intrinsic hardness increase of the alloyed silver matrix and possibilities to supersaturate the silver matrix by different alloying elements. Relationship between the hardness increase and ability for each solute species to distort the mean lattice parameters as functions of solute percent increase (at%) had been identified. Similar trends were observed for supersaturation and Lindeman-like melting behaviors. When solutes were added to the lattice, the lattice distortion was inevitable. Once the distortion exceeded a certain threshold, the lattice collapsed and led to a local melting event. When comparing with the solute addition (at%) our findings confirmed the same trends for the supersaturation rate (dC(critical)/d chi),the mean lattice distortion rate (dL(khl)/d chi), the increase rate in microvickers hardness (dHv/d chi), and the Lindeman melting behavior particularly the rate of drop in solidus temperatures (dT(solidus)/d chi).