Dynamic recrystallization behavior and strengthening mechanism of quasi-precipitate-free dilute Mg–Bi–Sn alloy

Abstract

In this study, a dilute Mg–0.5Bi–0.5Sn alloy system was designed and subjected to extrusion at a low temperature of 250 °C. The dynamic recrystallization behavior and strengthening mechanism of the extruded alloy were discussed in detail. At the initial stage of the extrusion process, the dynamic recrystallized grains were formed through twinning-induced dynamic recrystallization (TDRX), continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). In the middle stage of extrusion, the emergence of CDRX and DDRX were synergistic. In the later stage of extrusion, DDRX and CDRX were exclusive and DDRX was the dominant mode. For the dilute extruded Mg–0.5Bi–0.5Sn alloy, the ultimate tensile strength, tensile yield strength and elongation were 282 MPa, 212.4 MPa and 36.3%, respectively, reaching an excellent high strength-ductility balance. The enhanced strength has been an outcome resulting from grain boundary strengthening and texture strengthening, along with dislocation strengthening. Ductility enhancement is closely related to the easily activation of <c+a> slips, which can be ascribed to the relatively high Schmid factor.