Particle size dependent Ag precipitation at different temperature and the resultant oxidation behavior of Cu-5Ag powders

Ag precipitation and the resultant oxidation behavior of Cu-5wt.%Ag powder of various particle sizes were investigated. During low-temperature aging (250 ℃), Ag precipitation along grain boundaries (GBs) in particle surface is closely dependent on particle size. The depth of Ag precipitation-free area (Ag-PFA) are 0 μm, 1.17 μm and 2.78 μm for S, M and L samples, respectively. While for high-temperature aging (550 ℃), the Ag precipitation was independent on particle size. This is ascribed to that Ag diffusion in particles at low temperature is dominated by both surface diffusion and GB diffusion, while at the higher temperature, the volume diffusion also becomes dominant. The formation of a continuous 3D-Ag network along GBs in particle surface can significantly improve the oxidation resistance of powders.