Fig. 1. (a) Schematic diagram of the extrusion process for different samples; (b) the dimension of in-situ ER3.9 tension sample and (c) schematic of the in-situ tension device [20].

Fig. 2. SEM images of (a) the sample before SS, (b) the SS sample, and (c) EDS results of the precipitates at points A and B marked in (a); SEM images of the (d) ER12.8 sample, (e) ER6.4 sample, and (f) ER3.9 sample; optical micrographs of the (g) ER12.8 sample; (h) ER6.4 sample and (i) ER3.9 sample.

Fig. 3. EBSD inverse pole figure (IPF) maps, (0001) pole figures, and corresponding grain size distributions: (a)-(c) ER12.8 sample, (d)-(f) ER6.4 sample, and (g)-(i) ER3.9 sample.

Fig. 4. (a) Tensile true stress-true strain curves of the ER12.8, ER6.4, and ER3.9 samples; (b) development of tensile properties for various samples; (c) a comparison of strength and ductility between the present work and other extruded Mg alloys containing RE [[25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36]; (d) strain hardening rate as a function of true strain for various samples and the corresponding close-up view of the up-turns marked by a dotted box.

Fig. 5. SEM morphology of the fracture after tensile tests for (a) and (d) ER12.8 sample, (b) and (e) ER6.4 sample, and (c) and (f) ER3.9 sample.

Fig. 6. (a) Schematic diagram of the nucleation of DRX grain; (b) corresponding hot working stress-strain curve.

Fig. 7. Rare earth texture and rest texture component: (a) ER12.8 sample, (b) ER6.4 sample, and (c) ER3.9 sample.

Fig. 8. IPF maps (a) and GND maps (b) of ER12.8 sample at 0%, 2%, 4%, and 6% strains; the IPF maps (c) and GND maps (d) of ER3.9 sample at 0%, 2%, 4%, and 8% strains.

Fig. 9. Histogram distribution of GND density in ER12.8 sample (a), coarse grains (b), and fine grains (c) of ER3.9 sample at different strains; the change of GND density of ER12.8 sample (d) and coarse and fine grains of ER3.9 sample (f) at different strains; the increasing rate of GND density of ER12.8 sample (e) and coarse and fine grains of ER3.9 sample (g) at different strains.

Fig. 10. Evolution of heterogeneous texture between coarse and fine grains and SF distribution histograms of ER3.9 sample under 0%, 2%, 4%, and 8% strains: (a) and (b) coarse grains, (c) and (d) fine grains.

Fig. 11. (a) Superposition of SEM map on IPF map at Mg-13Gd. (b) Slip trace analyses on highlight grains 222, 326, 329, and 390 based on SEM map, EBSD maps, and theoretical slip trace directions after 5% strain. (c) Statistics of the identified slip activity in fine grains with 446 grains of Mg-13Gd sample and (d) corresponding SFs of the activated slip systems after 5% strain.

Fig. 12. Band contrast maps of (a) ER12.8, (b) ER6.4, (c) ER3.9 samples; (d) the misorientation map.

Fig. 13. (a) LUR tensile curves of ER12.8, ER6.4, and ER3.9 samples. (b) Partially enlarged hysteresis loops of different samples. (c) Schematic illustration of the partition of hetero-deformation induced stress (σHDI) and effective stress (σeff) in the loading-unloading cycle. The εae and εe are represented the anelastic recovery strain and the elastic recovery strain, respectively. The evolution of (d) HDI stress and (e) HDI hardening; (f) the effective stress of different samples with increasing tensile strain.

Fig. 14. Macroscopic strain distribution of (a) ER12.8, (b) ER6.4, and (c) ER3.9 samples during tension along ED; (d), (e), and (f) are corresponding average strain distribution curves along the designated paths L1-L6 at different tensile strains.

Fig. 15. (a) Optical micrographs of the selected region including coarse and fine grains marked by the black rectangle; (b) SEM images of speck markers used for DIC; (c) detailed distribution of the speck markers before and after deformation; (d) average strain distribution curves along ND; (e) microscopic strain (εxx and εxy) distribution in ER3.9 samples at different strains during tension along ED.

Fig. 16. TEM images of ER3.9 sample after 2% strain: (a) annular bright-field (ABF) image and (b) high-angle annular dark-field (HAADF) image of the microstructure in DRXed and un-DRXed regions; (c) and (d) are the corresponding magnification images, respectively.