Ultra-strong, ductile and thermally stable ultrafine grained 5083 Al alloy fabricated by high pressure torsion using pre-sintered powders

Abstract

This work developed a novel strategy that employed powder metallurgy, high pressure torsion and subsequent annealing treatment to prepare fully recrystallized ultrafine-grained (UFG) 5083 Al alloy. The fabricated specimens showed excellent thermal stability even at 773 K, which was mainly attributed to the fine Al6(Mn, Fe) precipitates and oxide dispersoids that reduced the driving force for grain boundary migration by pinning. The mechanical properties primarily depended on the grain size. The specimens with the average grain sizes ranging from 0.39 to 0.81 µm exhibited good balance of strength and ductility, and the highest yield strength (454 MPa) together with decent elongation (0.11) were achieved when the grain size is 0.39 µm. In addition to grain boundary strengthening, the dislocation source-limited hardening greatly contributed to the yield strength of the fully recrystallized UFG alloy. The extra-hardening mechanism as well as the unique features of deformation including distinct yield point and large Lüders band was investigated in detail.