Room-temperature grain boundary diffusion data measured from historical artifacts

Abstract Diffusion processes in typical metals are considered to be slow at room temperature but there are many applications for which very long-term use is envisaged and stability needs to be assured over a timescale of 10 000 years, where even slow processes can be important. It is clearly impractical to make diffusion measurements under controlled conditions for this length of time, so it is common to perform accelerated tests at higher temperatures and extrapolate the necessary information from the measurements so obtained. We have tested the validity of this type of extrapolation for room-temperature, grain boundary diffusion in the copper–silver system, by measuring low-temperature diffusion profiles in antique samples of Sheffield Plate. We present experimental measurements and analysis, along with a comparison to modern diffusivity data extrapolated in the usual manner.