Optimizing the thermal treatment for restoration of brittle archaeological silver artifacts

Abstract

Abstract Archaeological silver artifacts are often found to be brittle because of long-term corrosion. However, the restoration of brittle archaeological silver artifacts by thermal treatment has never been quantitatively and systematically studied due to the lack of sufficient experimental samples. Herein, the simulated Ag–Cu alloy flake samples with intergranular corrosion consistent with those brittle archaeological silver artifacts were prepared through two-step annealing and accelerated aging in Fe(NO3)3 + AgNO3 solution. The changes in the microstructure and mechanical strength (σbb, Eb, and HV) of the brittle samples after thermal treatments were studied with the help of SEM–EDS, metallographic observation, three-point bending tests, and microhardness tests. In addition, the most suitable conditions for the restoration of the brittle samples were summarized by the temperature–time (T-t) map obtained from a series of comprehensive thermal treatments. Moreover, the differences in microstructures and mechanical strength between the brittle samples annealed in an aerobic/anaerobic environment were revealed. This work provides an important reference for the restoration and conservation of brittle archaeological silver artifacts.

Keywords

• Embrittlement
• Archaeological silver artifacts
• Thermal treatment
• Conservation
• Intergranular corrosion