The Anti-tarnishing, Microstructure analysis and Mechanical properties of Sterling silver with silicon addition

บทคัดย่อ

An investigation on the anti-tarnish properties of 0-0.5%wt silicon-added sterling silver was preformed. Mechanical properties such as hardness and tensile strength were also studied. It was found that the surface of as-cast specimens using an investment (lost wax) process became brighter with increasing silicon content. The Anti-tarnish properties of silicon-added silver alloys obtained by inserting specimens under the atmosphere of sulfur was also improved when compared to the silver alloy without silicon. The Anti-tarnish properties also depend on the silver content. For example, an alloy with 95%wt Ag was better tarnish resistant than the 92.5%Ag alloy. However microstructural analysis indicated that with increasing silicon content the microstructure of the silicon-added specimens had a tendency to be a network structure which was formed by the copper silicon rich phase occurring at the grain boundary of the alpha grain (Ag rich phase). As a result, the hardness increased gradually and the ductility decreased significantly with only a 0.04% by weight increase in the amount of silicon.