Microstructure and mechanical properties of caliber rolled Mg-Y-Zn alloys

The microstructural evolution and mechanical properties were investigated using a caliber rolled Mg-5Y-2.5Zn (in at.%) alloy. Deformation kink bands could be induced by the caliber rolling process, which is the same as that of conventional wrought processed (extruded or rolled) Mg-Y-Zn alloys. The number of rolling passes was an influential factor for the microstructure, i.e., the bending angle of the long periodic stacking ordered (LPSO) phase associated with deformation kink bands. The mechanical properties of strength and hardness also depended on the number of rolling passes. These properties were improved with increased number of rolling passes (up to 6 passes). The yield strength and hardness before the rolling process were 260 MPa and similar to 90 Hv. On the other hands, after caliber rolling, these properties showed over 500 MPa and 129 Hv, respectively, for the alloy with 6 rolling passes. Microstructural observations revealed that such good properties resulted from the existence of deformation kink bands and dense dislocations induced by caliber rolling. Controlling the morphology of the LPSO phase associated with deformation kink bands was found to be an effective strategy; the bending angle of this phase of more than 20 degrees is outstanding for further improving the mechanical properties.