Notes on work hardening and recovery

Abstract

Although the available data are not conclusive, they suggest that the annealing processes in cold worked metals may be subdivided into at least three distinct stages, which occur successively with increasing annealing time or temperature (apart from overlapping) in the following order: 1. (1) recovery (without interface migration), 2. (2) sub-boundary migration (gradual subgrain growth essentially without reorientation) 3. (3) grain boundary migration (“recrystallization” with local reorientation, i.e., the discontinuous growth of some crystal fragments with strongly deviating orientations). It appears that most of the stored energy of cold work and a minor component of the work hardening is released in recovery, while subgrain growth is capable of releasing the remaining larger portion of work hardening, which is connected with the sub-boundaries. However, the third stage of annealing (“recrystallization”) often sets in prematurely and then it takes over from subgrain growth the function of relieving a large fraction of the work hardening.