Strengthening mechanisms in a Zr-modified 5083 alloy deformed to high strains

The effect of extensive grain refinement through equal-channel angular processing (ECAP) at 300 °C on the mechanical properties was examined in a Zr-modified 5083 aluminum alloy. It was shown that any increase in the yield stress (YS) by increasing the number of pressings was attributed to additional contributions from three strengthening mechanisms: (i) grain boundary strengthening related to the size of the crystallites bounded by deformation-induced high-angle boundaries (HAB), (ii) dislocation strengthening related to highly increased dislocation density and (iii) solute strengthening related to promoting dynamic strain aging (DSA) by intense plastic straining. Grain size strengthening is the primary contributor to the increase in the YS as a result of ECAP. Dislocation strengthening plays an important but minor role in strengthening the alloy after ECAP. No ECAP effect on the dispersion strengthening was observed. However, a dispersion of nanoparticles was found to cause an increase in the YS through grain refinement and the accumulation of lattice dislocations during ECAP. It was found that the deformation-induced low angle boundaries (LABs) play an insignificant role in the strengthening of the material.