The effect of hydrostatic pressure up to 9.5 kbar on the annealing rate of the excess resistivity in quenched aluminum was measured in two annealing regions. One was at —65°C following quenches from 580°C and the other at 0°C following quenches from 331°C. Effective activation volumes for motion were determined to be (3.0±0.3)×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^3$ and (2.8±0.3)×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^3$, respectively. These results were interpreted in terms of vacancy and divacancy motion. The -65°C anneal value represents the motion of divacancies. The 0°C anneal value cannot unambiguously be assigned to a single type of defect. However, assignment of a single-vacancy motional volume close to the 0°C anneal value is consistent with these and diffusion results if it is assumed that there is a divacancy contribution to self-diffusion in aluminum, or that the motional volume is temperature-dependent.

• Received 4 September 1969

DOI:https://doi.org/10.1103/PhysRevB.1.3922