Fig. 1. (a) Optical and (b) SEM micrographs of the homogenized AZ80 billet. davg denotes the average grain size.

Fig. 2. (a-c) Optical and (d-f) SEM micrographs of the extruded (a, d) AZ80-250, (b, e) AZ80-300, and (c, f) AZ80-350 alloys. fDRX denotes the area fraction of DRXed grains.

Fig. 3. EBSD results of extrusion butt of AZ80-250 alloy: (a) inverse pole figure (IPF) map; (b) grain orientation spread (GOS) map of the area marked in the schematic illustration of extrusion butt; (c-e) enlarged IPF maps of regions A, B, and C in (a); and (f) accumulative misorientation along the dotted line from point D to the grain boundary in (e). LABs, M, CT, and DT denote the low-angle boundaries, matrix, {10$\bar{1}$1} contraction twin, and {10$\bar{1}$1}-{10$\bar{1}$2} double twin, respectively.

Fig. 4. Number density and size distribution of unDRXed grains in the extruded alloys. The average and standard deviation of the size of unDRXed grains are listed in the inset table.

Fig. 5. Inverse pole figure maps showing the fine- and coarse-grained DRXed regions of the extruded (a) AZ80-250, (b) AZ80-300, and (c) AZ80-350 alloys. dfine-DRX and dcoarse-DRX denote the average grain sizes of the fine- and coarse-grained DRXed regions, respectively.

Fig. 6. ED inverse pole figures for the DRXed region of the extruded (a) AZ80-250, (b) AZ80-300, and (c) AZ80-350 alloys obtained from the EBSD results presented in Fig. 5.

Fig. 7. (a) Variation in the Al solubility limit (red line) with temperature for the equilibrium state of AZ80 alloy, as calculated using PANDAT software. The blue horizontal line in (a) represent the Al content of the AZ80 alloy (8 wt.%). (b) Electrical resistivity of the homogenized billet and extruded alloys and amount of Mg17Al12 precipitates in the extruded alloys. AZ80-H in (b) denotes the homogenized AZ80 billet.

Fig. 8. SEM micrographs showing precipitates of the extruded (a, d, g) AZ80-250, (b, e, h) AZ80-300, and (c, f, i) AZ80-350 alloys: (a-c) fine-grained DRXed region, (d-f) coarse-grained DRXed region, and (g-i) unDRXed region.

Fig. 9. (a) Average hardness of the unDRXed, fine-grained DRXed, and coarse-grained DRXed regions of the extruded alloys; (b) the variation in the relative contribution of each region to the overall hardness with extrusion temperature calculated from the area fraction and hardness of each region.

Fig. 10. Engineering stress-strain curves for the extruded alloys under (a) tension and (b) compression along the extrusion direction.

Fig. 11. Variation in the tensile yield strength (TYS), compressive yield strength (CYS), and yield ratio (CYS/TYS) of the extruded alloys with extrusion temperature. The green lines with arrows represent the difference between the TYS and the CYS.

Fig. 12. EBSD results of extruded AZ80-250 alloy: (a) inverse pole figure map and ED inverse pole figure of the unDRXed region; (b) GOS map of DRXed and unDRXed regions. SF{ 10$\bar{1}$2 } twin denotes the average Schmid factor for the {10$\bar{1}$2} twinning of the unDRXed region under compression along the extrusion direction.

Fig. 13. Optical micrographs showing {10$\bar{1}$2} twins formed during compression of the extruded (a, c) AZ80-250 and (b, d) AZ80-350 alloys subjected to 3% compression along the extrusion direction: (a, b) unDRXed region and (c, d) fine- and coarse-grained DRXed regions.