Recovery kinetics of nanostructured aluminum: Model and experiment

A model is suggested which, for a deformed and partially annealed material, can factor out the recovery component of the flow stress for conditions where recrystallization occurs simultaneously with recovery processes. The model is applied in an analysis of the isothermal rates of recovery of hardness upon annealing of commercial purity aluminum at temperatures between 140 and 220°C of samples cold rolled to strains 2 and 4.

This analysis is successfully validated by a microstructural characterization. The recovery rates are described by a first-order chemical reaction rate equation with an activation energy that varies from 89kJmol−1 at the onset of recovery to 125kJmol−1 at its conclusion. The recovery rate increases significantly with an increase in strain, thereby markedly reducing the thermal stability of the material deformed to the largest strain.