Annealing-induced strengthening and stabilization in ultrafine-grained Al and Al–Mg alloys prepared by rapid powder consolidation

Abstract

Annealing usually softens Al–Mg based alloys due to grain coarsening. This work shows that annealing induces strengthening in bulk ultrafine-grained Al and Al-(2.5, 5 and 7.5) at.% Mg samples fabricated by mechanical alloying and rapid powder extrusion. Experimental investigation of the microstructure of the annealed samples reveals that the annealing promotes in-situ formation of nanoscale dispersoids which strongly suppresses grain growth and recrystallization. The in-situ formed nanodispersoids warrant high thermal stability of the ultrafine-grained matrix microstructure and improve the strength of the as-extruded samples while maintaining their good ductility. The present findings offer an exciting pathway in developing thermally stable ultrafine-grained Al–Mg based alloys with a notable combination of high strength and good ductility. © 2021 Elsevier B.V