• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.5
• /
• pp.1547-1551
• /
• 2010

We newly propose the silver alloys of Ag-5wt%Ge-2.5wt%Cu(Ge1) and Ag-5wt%In-2.5wt%(In1) to overcome the tarnish and mechanically weak problems of the conventional sterling silver Ag-7.5wt%Cu (Cu1). We check the castability, surface color stability during process and wearing, and work hardening with plastic deformation of all three silver alloys. Our newly proposed silver alloys of Ge1 and In1 showed improved castability, anti-tarnish stability, and work hardening property compared to the conventional sterling silver, which implied that these alloys might be more appropriate for the high-end silver jewelry.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.382-389
• /
• 2019

A novel folding process is proposed using a repeated cold-die forging and annealing to form a sterling silver ring. Sterling silver plate was cut into a doughnut shape, and lattices with 0.43-mm line-width were imprinted on it. The sample was folded by forging using dies with slopes of $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$ and annealing. For comparison, samples were also fabricated without annealing. Strain was identified by measuring the length of lattices. Vernier calipers, a Vickers hardness tester, an optical microscope, and a UV-VIS colorimeter were used to determine the size, hardness, microstructure, and body color. Without annealing, cracks occurred. However, successful deformation was possible when annealing was used. The results of macro strain measurements show that the outer diameter and width decreased, while the inner diameter and thickness increased after the final process. The maximum strain was increased 0.128 toward the parallel direction. The Vickers hardness decreased after annealing and increased after the folding process. The microstructure results showed that the grain size increased after annealing but decreased after folding. The color difference based on the Lab index was under 10 for all processes. Eventually, a doughnut-shaped silver plate was successfully deformed into a ring shape by the folding process.