Annealing-Induced Grain Refinement and Hardening in Ultrafine-Grained Al and Al-Mg Alloys

This work shows that the elongated grains that contain subgrains in bulk ultrafine-grained Al and Al-(2.5, 5 and 7.5)at.%Mg samples, fabricated by mechanical alloying and rapid powder consolidation, recrystallize to develop finer equiaxed matrix grains during subsequent annealing. The annealing also promotes formation of nanoscale oxide particles. The high number density oxide nanoparticles and fine recrystallized grains warrant high thermal stability and enhanced strength of the annealed samples while maintaining the good ductility of their as-extruded counterparts. The present experimental findings offer an exciting pathway in developing high thermal stability ultrafine-grained Al-Mg based alloys with a notable combination of high strength and good ductility.