Abstract:
To study mechanical properties for instance hardness and tensile strength, and tarnish resistance of sterling silver having 0 to 0.11 % silicon by weight (as from copper-silicon alloy) and 0 to 2.13% indium by weight. The sterling silver melts were prepared in air and argon at 1373 K. The samples were taken for chemical analyses, microstructure, mechanical properties and tarnish resistance testing. The tarnish resistance test were carried out by hanging the samples on a closed chamber containing saturated aqueous of sodium sulfide. The discoloration was evaluated by spectrophotometer. The results showed that effects of indium added sterling (1.03-2.09 % indium) in improving tarnish resistance was not noticeable. In addition, the alloy exhibited lower tensile stress and hardness due to lower copper content. The secondary structure was found to increase in voloume and was well dispersed as more indium was added. For sterling silver having silicon 0.09-0.11% by weight and indium 0.53, 1.09, 1.60 and 2.13%, the tarnish resistance of these alloy was found to increase as the amount of indium increased. The tarnish resistance was found to increase 33-40% compared with the common sterling silver (92.50% sterling silver) and 31.84-38.65% compared with the silicon added sterling silver (0.09-0.11% silicon). EDX revealed that both indium and silicon presented in both the matrix and the secondary structure.