Significant improvement in the mechanical properties of an extruded Mg–5Bi alloy through the addition of Al

Abstract

This study demonstrates that the addition of Al to an Mg–5Bi alloy effectively promotes dynamic recrystallization during hot extrusion and significantly improves the mechanical properties of the extruded alloy. When the Al content increases from 0 wt% to 9 wt%, the area fraction of recrystallized grains increases from 69.3% to 100%, which can be attributed to the greater number of recrystallization nucleation sites due to grain refinement of the billet, enhanced particle-stimulated nucleation due to the greater abundance of undissolved particles, and the facilitation of dislocation accumulation due to the lower stacking fault energy. The addition of Al also simultaneously improves the microstructural homogeneity, tensile and compressive strength, ductility, and yield symmetry of the extruded alloys. The tensile yield strength × elongation value of the extruded material dramatically increases from 412 to 3489 MPa∙% with the addition of 6 wt% Al to the Mg–5Bi alloy. The variation in dynamic recrystallization and dynamic precipitation behaviors with changes in Al content and the association between the microstructural characteristics and mechanical properties of the extruded alloys are discussed in detail.