Microstructure and mechanical property evolution of 99.1% recycled aluminum during equal Channel Angular Extrusion

Abstract

A 99.1% recycled aluminum was severely deformed by equal channel angular extrusion (ECAE) using two different processing routes BC and C, to study the evolution of the microstructure and associated changes of mechanical properties.The analysis of microstructure before and after ECAE for three orthogonal planes X, Y and Z, showed a significant variation of grain shape, which depend on the plane type and processing route. The analysis of X-ray diffraction peaks showed a significant broadening after ECAE. This is due to grain refinement and lattice distortions. A shift of the peaks is also observed, which was related to residual compressive stress caused by the ECAE. An important decrease of the lattice parameter was observed after the first passage, then it increases for subsequent numbers of passages; the increase is however, more important in the specimens extruded via route C. This is due to a high density of dislocations introduced by deformation via this route what generates a dynamic recovery during ECAE process. Changes in mechanical behavior are observed after ECAE. The yield stress and Vickers hardness increase with the number of passes. This is due to strain hardening.