Surface vacancy pits and vacancy diffusion in aluminum

Abstract

The width of regions depleted of vacancy pits, (1) near various grain boundaries, were measured in aluminum for several temperatures of pit formation. These measurements, combined with the measured temperature-time relation during pit formation, allow one to evaluate the activation energy, . E m , for vacancy diffusion. In the present study it was found that E m = 17 + 1 rm kcal/mole for aluminum. Boundaries with disorientation angles ranging from 2° to 50° were found to be equally effective sinks for vacancies, which indicates that this property is not sensitive to the details of boundary structure. A comparison of the pit density with the dislocation density shows that these pits do not necessarily nucleate at the intersections of dislocations with the surface.