Enhancement of toughness by grain boundary control in magnesium binary alloys

The mechanical properties, i.e., strength and toughness, were investigated on five fine-grained Mg-0.3 at% X (X=Al, Ca, Sn, Y and Zn) alloys by two different processes: extrusion and caliber rolling. The extruded and caliber rolled alloys had the same texture distribution, but different grain boundary structures. The caliber rolled alloys, which had high fraction of low-angle grain boundaries, showed higher toughness and larger void size as compared to those of the extruded alloys, regardless of the alloying elements. The low-angle grain boundaries played a role in suppression of micro-void nucleation site. Thus, the control of grain boundaries is an effective method to enhance the mechanical properties in magnesium alloys, especially toughness. Importantly, the addition of aluminum or zinc elements in the caliber rolled alloys was the most effective in improving the strength and toughness balance among the well-known binary alloying elements.