TEM and stress relaxation analysis of 99.1% aluminum processed by Equal Channel Angular Extrusion

Abstract

Relaxation experiments were performed on 99.1% aluminum in addition to transmission electron microscopy and mechanical tests to follow the evolution of the microstructure and the mechanical properties changes after equal channel angular extrusion (ECAE). After deformation, weak beam investigations were conducted on selected specimens. The microstructure of deformed material shows the presence of almost parallel and elongated grains. Moreover, newly created subgrains separated by dislocation walls are observed. The tensile and Vickers hardness experiments for deformed samples showed an improvement of mechanical properties compared with the unextruded one. The activation volume, obtained from relaxation tests decreases with increasing the number of passes. This is due to change in mechanism from dislocation-dislocation interaction in coarse grains material (N = 0) to dislocation-grain boundary or grain deformation in ultra fine grains material (N≥1).