The Study on Microstructure and Mechanical Properties of Silver alloy 58.4% for Jewelry Manufacturing

Abstract

The research involved the characterization of the properties of silver alloys -bearing copper and zinc. The alloys composed of 58.4% silver 20.85-41.76% copper and 0-20.83% zinc, respectively. When comparing the characteristics of this alloy and sterling silver 925, the alloy specimen had mechanical properties better than the sterling silver 925. The alloy tests presenting the mechanical values of the hardness, shear bond strength, elasticity of the specimen were in a range of 54.6-95.3 HV1, 209.5-379.3 MPa., 100.6-193.8 MPa. and 32.1-51.7%, respectively. While the mechanical values of sterling silver 925 were 52.8 HV1, 193.5MPa., 96.0 MPa. and 29.8%, respectively. Besides these, the microstructure of the alloy specimen showed the dendrite structure. We found that this structure decreased when the concentration copper in the specimen increased. After adding zinc into the alloys, the high amount of zinc caused the zinc-rich (alpha) phase changed to Eutectic phase, together with the significantly increased area of alpha phase. These effects, therefore, brought up the better various mechanical properties of the alloys. At the same time, the another test specimen composed 58.67% Ag 39.20% Cu and 2.14% zinc. The color level of this specimen was close typically to the sterling silver 925, with the difference of Da at 0.236 and Db only at 5.268. Additionally, the higher copper concentration in the alloy provided a value tentatively increased but b value decreased. However, more remarkable results were that the zinc showed opposite effects from the copper.