High-temperature creep of nickel under conditions of grain-boundary diffusion of impurities from the surface

Abstract

Comparative investigations of the effect of diffusion streams of copper atoms (a weakly segregating impurity) and silver atoms (a strongly segregating impurity) from the surface in the high-temperature plastic deformation of nickel have been carried out. It has been established that in the high-temperature plastic deformation of nickel, when there are diffusion streams of copper and silver from the surface, there is a reduction in the creep resistance of nickel due to an increase in the contribution of grain-boundary slip to the overall deformation. Two stages, characterized by different values of the rate sensitivity factor m, are observed on the curve of the stress against the rate of deformation over a certain temperature range for each impurity. In the region of deformation rates of$\dot \varepsilon< 2.5 \cdot 10^{ - 6}$ sec⁻¹, m≊0.2, and for$\dot \varepsilon > 2.5 \cdot 10^{ - 6}$ sec⁻¹, m becomes less than 0.05.