Achieving ultrahigh strength in binary Al-10Mg alloy through heavy cryogenic rolling

Abstract

Al-Mg alloys with high Mg contents have attracted considerable interest given enhanced strength and simultaneously reduced density by high Mg solute concentrations. In the present study, we proposed a strategy of strengthening Al‐10wt%Mg binary alloy via heavy cryogenic rolling at liquid nitrogen temperature. Both cryogenic plastic deformation and a high concentration of Mg solute effectively suppress dynamic recovery during rolling, creating nanoscale and ultra-fine laminated grains containing a high density of dislocations in a nearly single-phase solid solution. The as-rolled Al‐10wt%Mg exhibits an average 0.2% offset tensile yield strength of 619 MPa, and average engineering and true ultimate tensile strengths of 689 and 726 MPa, accompanied by average uniform elongation of 5.3% exceeding the threshold value of 5% required for structural engineering applications. The high strength stems from enhanced solid-solution strengthening of a high concentration of Mg solute, significant grain boundary strengthening of nanoscale and ultra-fine laminated grains, and strong dislocation strengthening. The appreciable ductility can be primarily attributed to a high concentration of Mg solute that can retard dynamic recovery processes during tensile testing by impeding dislocation motion, thus enhancing dislocation accumulation and work-hardening ability. A high concentration of Mg solute combined with cryogenic plastic deformation to a high strain magnitude provides a new avenue to achieve ultrahigh strength and good ductility in non-age-hardened Al-Mg alloys.