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.
Highlights
Silver, because of its excellent ductility, malleability and aesthetic appearance, has been widely used in the production of ancient artifacts [1]
Preparation of the simulated Ag–Cu alloy flake samples To study the effect of thermal treatments on brittle archaeological silver artifacts, we need to prepare simulated Ag–Cu alloy flake samples with intergranular corrosion
In our former work [10], we studied the composition and microstructure of a brittle archaeological silver artifact unearthed from Guizhou Province, China, and found intracrystalline red-brown particles with high Cu and O contents in the dark field, which can be considered key evidence of whether the simulated samples we prepared conform to the similar microstructure of archaeological silver artifacts [37]
Summary
Because of its excellent ductility, malleability and aesthetic appearance, has been widely used in the production of ancient artifacts [1]. Thermal treatment is a common and effective method for the restoration of brittle archaeological silver artifacts at present, regardless of the conservation concept controversy that it might bring about. Liu et al Heritage Science (2022) 10:21 high-temperature torch to directly anneal the surface of the silver fragments to reduce embrittlement and restore their mechanical strength and bending resistance. This approach has been found to be effective in terms of restoration results, our preliminary research has shown that such a thermal treatment method (by hightemperature torch) may lead to some subsequent potential problems (Additional file 1: Fig. S1). Due to the lack of sufficient experimental materials for quantitative study, no systematic research has been carried out far
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