Fig. 1. Optical micrographs of the as-extruded alloys observed at (a-b) longitudinal and (c-d) transverse sections: (a, c) FE sample, (b, d) FHE sample. (The areas marked by red and blue elliptical dotted lines represent the unDRXed grains and DRXed grains, respectively. The phases marked by red and blue arrows represent the plate-shaped LPSO phases and the block-shaped LPSO phases, respectively.).

Fig. 2. (a-d) EBSD results and KAM maps (e, f) of the as-extruded alloys obtained from (a, b) longitudinal and (c-f) transverse sections: (a, c, e) FE sample and (b, d, f) FHE sample.

Fig. 3. Mean KAM values of the (a-c) FE sample and (d-f) FHE sample: (a, d) whole regions; (b, e) unDRXed regions; (c, f) DRXed regions.

Fig. 4. TEM bright-field micrographs and corresponding SAED patterns taken from the (a, b) unDRXed and (c, d) DRXed regions of the as-extruded alloys: (a, c) FE sample, (b, d) FHE sample. (The broken block-shaped LPSO phases are marked by blue arrows, and the yellow arrows represent β phases.).

Fig. 5. SEM micrographs of the (a) FH sample and (b) FHE sample taken from the transverse sections, and (c-e) EBSD analysis of the selected area and the corresponding (0001) pole figure.

Fig. 6. Inverse pole figures of the as-extruded alloys along extrusion direction: (a-c) FE sample and (d-f) FHE sample.

Fig. 7. Age-hardening curves of the extruded alloys at 200 ℃.

Fig. 8. Microstructure observation of the peak-aged (a, c, e) FEA and (b, d, f) FHEA samples on the transverse sections: (a, b) SEM micrographs, (c, d) EBSD IPF maps, (e, f) Kernel Average Misorientation maps.

Fig. 9. TEM bright-field images and corresponding SAED patterns taken from the (a, c) DRXed and (b, d) unDRXed regions of the peak-aged alloys: (a, b) FEA sample, (c, d) FHEA sample.

Fig. 10. Tensile nominal stress-strain curves of the samples tested at RT.