Relationship between Cluster-Arranged Nanoplate Formation and Mechanical Properties of Dilute Mg-Y-Zn Alloys Prepared by Combination of Low-Cooling-Rate Solidification and Extrusion Techniques

High-strength dilute Mg-Y-Zn alloys with cluster-arranged layer/nanoplate (CAL/CANaP) precipitates were developed via combined processes of low-cooling-rate solidification and extrusion techniques. The effects of CANaP morphology and deformation kink bands installation on the tensile properties of the extruded Mg-Y-Zn alloys were investigated. A slow-cooling solidification process with a cooling rate range of 0.1-0.01 K center dot s11 produces a CAL-aggregated region in the a-Mg matrix. The CAL-aggregated region comprises long-period stacking ordered (LPSO) nanoplates with an intergrowth structure and the solo-CAL precipitates. The area fraction of the CAL-aggregated region increased with decreasing cooling rate. The microstructure of the extruded Mg99.2Y0.6Zn0.2 alloys prepared from low cooling rate-solidified ingots consisted of three characteristic regions: (i) dynamically recrystallized (DRXed) fine a-Mg grains, (ii) worked coarse a-Mg grains with a CAL-aggregated region, and (iii) worked blocky LPSO grains. The strength and ductility of the extruded Mg-Y-Zn alloys may be controlled by the volume fractions of the worked and DRXed grains, respectively. It is desirable to control the CANaP thickness and spacing to ,-1 mu m and ,-0.8 mu m or more, respectively, to promote DRX. Conversely, it is necessary to control the CANaP thickness and spacing to ,-1 mu m and ,-0.8 mu m or less, respectively, to form the worked grains in which kink bands are introduced.