Anelastic Study of Nanocrystalline Gold Prepared by Gas Deposition Method

Abstract
To pursue insight into the characteristic mechanical property of nanocrystalline (n-) Au prepared by the gas deposition method, we investigated anelastic properties after 20 MeV proton irradiation at 1.5 to 5 K. No dislocation pinning is observed during irradiation and warm-up after irradiation, suggesting that the dislocation density is negligibly low in the present high-density n-Au specimens. Instead, the Young's modulus E_b at 1.5 K shows a decrease during the early stage of irradiation which is followed by an increase in the later stage of irradiation. The magnitudes of the early decrease and the later increase in E_b are variable among the specimens but they are reproducible for repetition of irradiation when the effects of preceding irradiation are canceled by annealing. The combination of these results, the effects of annealing on E_b and the irradiation data compiled for the bulk Au suggests that the strong changes in E_b are due to probable local shear deformations of certain agencies existing in the grain boundary regions.