X-ray studies of structure defects in recycled aluminum alloy during equal channel angular extrusion: Dislocation density and stored energy

A recycled aluminum alloy was severely deformed by Equal Channel Angular Extrusion (ECAE) using the processing route Bc, to study the evolution of the micro structure and associated changes of mechanical properties. XRD patterns were analyzed to determine crystallite size, lattice strain and lattice parameter. As a result, ultrafine grains material has been obtained with microstructure showing a mixture of highly strained crystallites. High density of dislocations is achieved as a result of severe plastic deformation through the die. This can explain an important decrease of the lattice parameter observed after the first passage. Changes in mechanical behavior are also reveled after ECAE. This is due to strain hardening. Differential Scanning Calorimetry (DSC) results show overlapped exothermic peaks indicating the succession of the recovery, recrystallization and grain growth phenomena's. Moreover, we demonstrate that the energy stored during ECAE can be related to the dislocation density introduced by severe plastic deformation.