Microstructure evolution, mechanical property response and strengthening mechanism induced by compositional effects in Al–6 Mg alloys

Abstract

Based on the compositional design concept, an Al–6 Mg–0.8Mn (–0.2Sc) alloy with a good combination of strength and ductility was obtained by hot extrusion deformation with a large extrusion ratio. The microstructure evolution and mechanical property of an Al–6 Mg alloy with adding Mn and/or Sc elements were investigated. The results showed that the addition of Sc element resulted in the grain refinement and promoted the precipitation of nano-sized Al6Mn phases in the Al–6 Mg–0.8Mn–0.2Sc alloy. After hot extrusion, the number of nano-sized Al6Mn phases decreased with the morphology transforming into the rhomboidal/plate-like shape. The combined effect of nano-sized Al6Mn phases and Al3Sc dispersoids offered a strong pinning effect on both grain boundaries and dislocations, leading to a significant refinement for recrystallized grains. Strengthening mechanism analysis indicated that the grain boundary and dislocation strengthening play important roles in enhancing the yield strength of the alloy. In addition, the uniform distribution of solid solution Mg atoms and high recrystallized fraction contributed to the high ductility of the extruded alloy. The aim of this work is to provide a strategy to acquire Al–Mg alloys with excellent mechanical performance.