Fig. 1. (a) A representative EBSD map of the homogenized Al-7Mg alloy, (b) a typical TEM-based orientation map (Nanomegas-ASTAR), (c) the corresponding KAM map, (d) the grain size distribution and (e) the GB misorientation angle distribution of the as-ECAPed Al-7Mg alloy; inserts in (a) and (c) are the corresponding grain size distribution and local misorientation angle distribution, respectively, while the one in the bottom right is the color coded map of crystal orientations parallel to ND.

Fig. 2. Misorientation profiles measured along lines L1-L4 in Fig. 1(b). The black lines show the point-to-point misorientation while the red lines show the point-to-origin misorientation.

Fig. 3. Typical TEM images of the as-ECAPed Al-7Mg alloy. The inserts in (a) and (b) are the corresponding grain size distribution and representative SAD pattern, respectively.

Fig. 4. XRD patterns of the Al-7Mg alloy: (a) in the as-homogenized state and (b) in the as-ECAPed state. For comparison, theoretical diffraction peak positions of pure Al (lattice constant a = 4.0412 Å [35]) are included and presented as vertical dotted lines.

Fig. 5. APT analyses of the as-ECAPed Al-7Mg alloy: (a) and (d) element distribution maps, where Al (blue) and Mg (pink) atoms are presented; (b), (c) and (e) concentration profiles showing the local Mg distribution along GBs.

Fig. 6. The microhardness evolution of the ECAPed Al-7Mg alloy annealed at different conditions: (a) at various temperatures for 30 min, (b) at 200 and 275 ℃ with increasing time and (c) at 300 ℃ with increasing time.

Fig. 7. Typical EBSD maps of the ECAPed Al-7Mg alloy annealed at: (a) 200 ℃ for 30 min, (b) 250 ℃ for 30 min and (c) 200 ℃ for 24 h. The insert in the bottom right is the color coded map of crystal orientations parallel to ND.

Fig. 8. Typical EBSD maps of the ECAPed Al-7Mg alloy annealed at 275 ℃ for (a) 75 min and (b) 8 h. The insert in the bottom right is the color coded map of crystal orientations parallel to ND.

Fig. 9. Typical EBSD maps of the ECAPed Al-7Mg alloy annealed at 300 ℃ for (a) 30 s, (b) 60 s and (c) 300 s. The insert in the bottom right is the color coded map of crystal orientations parallel to ND.

Fig. 10. XRD patterns of the ECAPed Al-7Mg alloy annealed at different conditions: (a) at 200 ℃ for 24 h, (b) at 250 ℃ for 30 min, (c) at 275 ℃ for 75 min and (d) at 300 ℃ for 30 s. For comparison, theoretical diffraction peak positions of pure Al (lattice constant a = 4.0412 Å) are included and presented as vertical dotted lines.

Fig. 11. TEM images of ECAPed samples annealed at: (a-c) 250 ℃ for 30 min and (d-f) 200 ℃ for 24 h. Inserts in (a) and (d) are the corresponding grain size distribution charts while these in (b) and (e) are the corresponding SAD patterns.

Fig. 12. (a) The change in average grain size with annealing time at 200-300 ℃ and (b) corresponding grain growth exponent at different temperatures.

Fig. 13. Representative KAM maps of ECAPed Al-7Mg samples annealed at: (a) 200 ℃ for 30 min and (b) 275 ℃ for 8 h.