High Temperature Internal Friction in Cu-Ag Alloys

Abstract

Internal friction measurements by an inverted torsional pendulum apparatus with the frequency of about 1 Hz were carried out in the temperature range of 300 to 850°C for Cu-0.71% Ag, -1.77% Ag, and -3.55% Ag alloys.
In 0.71% Ag alloy a grain boundary peak was observed at about 550°C; the activation energy was estimated at 37±5 kcal/mol. In 1.77% Ag alloy a peak appeared at 660°C, but it showed no grain size dependence. In 3.55% Ag alloy, besides a grain boundary peak at about 550°C, another peak was observed at 710°C on heating and at 660°C on cooling. The latter peak, the height of which depended on the frequency and the cooling rate, was supposed to be a precipitation peak other than the relaxation-type peak. The height of the peak at 550°C decreased with increasing cooling rate, presumably due to the suppression of grain boundary migration by supersaturated solute atoms near the grain boundary.