Dynamic recovery in aluminum

Abstract

Dynamic recovery was studied in pure aluminum specimens deformed in tension at temperatures between 200° and 573° K, and strain rates between 0.004 and 2 min −1. The dislocation interactions and substructures were observed by means of thin-foil transmission electron microscopy. Activation energies were obtained for dynamic recovery and for tensile deformation. The values for deformation are ΔH d = 22.5 ± 3.5 kcal/ mol (at low temperatures) and ΔH d = 37.5 ± 2.5 kcal/ mol (at high temperatures). These two activation energies are related to the rate-controlling controlling processes of cross-slip and dislocation processes of cross-slip and dislocation climb, respectively. Thus, the activation energy for dynamic recovery, ΔH r = 22 ± 2.8 kcal/ mol, corresponds to the cross-slip of screw dislocations, which leads to the formation of stable dislocation networks and dislocation-free subgrains. At higher deformation temperatures, dislocation climb predominates, and subboundary disintegration and coalescence of subgrains are observed.