TEM and DSC Investigation of the Recovery of a Recycled Aluminum Processed by Equal Channel Angular Extrusion

TEM investigation was performed on a recycled aluminum processed by Equal Channel Angular Extrusion. The aluminum contains many inclusions which were identified to be rich in iron and silicon.This has a substantial effect in dragging recovery. ECAE was performed via routes B and C using a die formed by two channels characterized by the well defined angles =90° and  = 90°. The evolution of the microstructure seems to be similar whether using route B or C. a high dislocation density was introduced since the first passage together with a high density of Frank dislocation loops. The latter are due to a by-passing of inclusions by cross-slip mechanism. Weak beam experiments enable us to investigate the early stages of recovery consisting in the formation of dislocation walls and few dislocation cells. A partial arrangement of dislocations was observed since the first passage through the die. The formation of dislocation cells began already before annealing and progresses at more elevated temperatures. The substantive recovery seems to push recrystallization process to high temperatures. By contrast, DSC investigations show a significant difference: The amount of energy deduced from the area of the peak relative to recrystallization is higher when using route C.