Non-basal Slips Mediated Dynamic Recrystallization Promote Synergistic Strengthening and Toughening of Centrifugal Casting Mg–1.1Mn–0.5Al Alloy via High Strain Rolling

The synergy of excellent yield strength and ductility has always been a dilemma for conventional rolled magnesium alloys. In this paper, the contributions of alloying elements, deformation twinning and recrystallization to strengthening and toughening of the high strain rolled Mg–1.1Mn–0.5Al (wt%) alloys with variable rolling passes (1, 2, 4 and 7) at low temperature (473 K) were revealed. The results showed that the pyramidal slips mediated dynamic recrystallization was prone to promote synergistic strengthening and toughening of the high strain rolled Mg–1.1Mn–0.5Al alloy. The progressive microstructure evolution was characterized with increasing rolling passes by the dominant { 10 1 ¯ 2 } tension twins, the balanced distribution of { 10 1 ¯ 2 } , { 10 1 ¯ 1 } , { 10 1 ¯ 3 } , { 10 1 ¯ 1 } - { 10 1 ¯ 2 } , { 10 1 ¯ 3 } - { 10 1 ¯ 2 } and { 10 1 ¯ 2 } - { 10 1 ¯ 2 } multi-system twins, the mixed twinning dynamic recrystallization, discontinuous dynamic recrystallization, continuous dynamic recrystallization and the complete recrystallization grains, finally resulting in significant grain refinement to 4.72 μm. It was experiment confirmed that the massive evenly distributed compression twins accompanied by the high slips activity were able to coordinate local plastic deformation with each other so as to accommodate high strain rolling, promote strain softening effect and accelerated recrystallization rather than become a source of cracks during high strain rate rolling. Thanks to the micro and nano sized α-Mn and Al 8 Mn 5 precipitates, which brought out an activation of non-basal slip and accelerated recrystallization additively, the recrystallized Mg–1.1Mn–0.5Al alloy with excellent yield strength (~ 311 MPa), ultimate tensile strength (~ 378 MPa) and fracture elongation (~ 20.4%) were obtained via 7 passes rolling without annealing. Graphical Abstract