The Zener relaxation and vacancy-controlled atomic mobility in AgZn solid solutions-II The kinetics of vacancy annealing

Abstract

AgZn alloys containing 24-33 at.% Zn have been down-quenched from temperatures of 200°C or below to aging temperatures of 90°C or above, to produce initial quenched-in vacancy concentrations in the range 5 × 10-9 - 10-11 mole fraction. The subsequent decay of the vacancy supersaturation has been determined from analysis of Zener relaxation data obtained by a delayed creep method. In high purity well-annealed specimens, the vacancy decay occurs inhomogeneously and with kinetics that correspond well to the simple migration of vacancies to fixed sinks. In such samples the mean vacancy lifetime is as large as 2 × 1010 jumps. A small amount of plastic deformation or a less thorough preparatory anneal reduces the lifetime by 2 decades. Vacancy trapping effects due to oxygen and tin were looked for but not found. On the other hand, bismuth at a concentration of 10-4 was discovered to modify the annealing behavior in a manner indicating strong vacancy trapping. The vacancy-trap binding energy is estimated to be 0.3 eV. It is thought that the traps may consist of bismuth pairs, rather than single bismuth atoms. © 1968.