Recovery of low-temperature flow stress in zone-refined aluminum single crystals

The recovery of flow stress in zone-refined aluminum single crystals, deformed at −196 °C in uniaxial tension along the 〈1 1 1〉 direction, has been measured at temperatures between 0 and 200 °C after straining to flow stresses ranging from 7 to 30 ksi (48-207 MPa). The corresponding strains ranged from 1.2 × 10−2 to 13.1 × 10−2. The effects of pre-stress and recovery temperature on structure and flow stress after recovery were systematically evaluated. The measured activation energy for recovery was found to increase linearly with the extent of recovery. The flow stress after recovery is found to be proportional to the reciprocal of the square root of the cell diameter. These results are used to provide, in a self-consistent manner, a new model for the recovery process.