The Microstructure Characteristics Evolution of Bulk High-Purity Silver for High Relief Application

Silver products with high relief have become popular in the silver decoration industry. However, it is difficult to obtain these products through conventional processing at ambient temperature. The aim of this work is to solve this problem by increasing the deformation temperature. Detailed studies were conducted on the evolution of microstructure characteristics in bulk high-purity silver by electron backscatter diffraction (EBSD) to achieve high-relief applications at elevated temperatures. The high temperature sample is mainly composed of recrystallized and substructured grains, exhibiting a more stable state than the ambient temperature sample. More than 70% annealing twins are observed in the hot-working sample. They are characterized by the amount of sigma 3(n)-type triple grain boundary junctions within large grain clusters formed by multiple twinning. These particular boundaries improve the intergranular corrosion resistance and degradation, which is significantly essential for high-purity silver jewelry exposed to sweat and air. The closed multi-coining processes at different temperatures were conducted subsequently. The performance of workpieces demonstrates that increasing the deformation temperature is a viable alternative for producing durable high-relief silver products.