The Zener relaxation and vacancy-controlled atomic mobility in AgZn solid solutions—I Vacancy formation and migration energies

Abstract

New experiments are reported on the Zener relaxation in AgZn alloys (24–33 at.% Zn), both under conditions of vacancy equilibrium and after quenching from 200°C or below. The equilibrium measurements are concerned with the temperature dependence of the relaxation strength, the mean relaxation time, and the width of the relaxation spectrum. Small but interesting differences are noted between these results and those of earlier work. Using a novel “delayed creep method” for quenched specimens, it has been shown that the equilibrium vacancy concentration and the vacancy jump rate in these concentrated alloys are well represented by simple exponential functions of the reciprocal absolute temperature, involving respectively an effective formation and migration energy H ̄ f and H ̄ m . Over the range 24–33 at.% Zn, H ̄ f is found to drop slightly from 0.88 to 0.83 (±0.02) eV, while the corresponding values for H ̄ m are 0.56 and 0.54(±0.02) eV. These values are in striking contrast to previously reported values for similar alloys, but are judged to be more nearly correct. It now appears that the addition of Zn to Ag causes H ̄ f and H ̄ m to decrease in a manner such that their ratio H ̄ f H ̄ m maintains an approximately constant value of 1.5.