Fig. 1. Microstructures of GLWZ8431 alloy in the (a) as-cast, (b) T4-treated and (c, d) as-extruded conditions. Note that Fig. 1(a-c) shows the OM images, while Fig. 1(d) shows the SEM image of the studied alloy.

Fig. 2. X-ray diffraction patterns of GLWZ8431 alloy in the as-cast, T4 treated and as-extruded conditions.

Fig. 3. Microstructures of GLWZ8431 alloy in the T4-treated condition. Note that Fig. 3(a) and (b) shows the HAADF-STEM images of α-Mg matrix and the corresponding SAED pattern with B//[0001]α, Fig. 3(c) shows the BF-TEM image of bulk Mg3RE phase and corresponding SAED pattern with B// $[\bar{1}11]_{Mg_{3}RE}$, and Fig. 3(d) shows the HAADF-STEM image and EDXS mapping of selected area in Fig. 3(c).

Fig. 4. EBSD result of as-extruded GLWZ8431 alloy. (a) IPF map; (b) Grain boundary map; (c) Twin map; (d) Pole figure. Note that ETs refers to the extension twins, CTs refers to the contraction twins and STs refers to the secondary twins.

Fig. 5. (0001) and ($10\bar{1}0$) pole figures of as-extruded GLWZ8431 alloy.

Fig. 6. TEM images of Mg3RE phase variants in the as-extruded GLWZ8431 alloy: (a and d) BF-TEM image and corresponding SAED patterns of bulk Mg3RE particles; (b and e) BF-TEM image and corresponding SAED patterns of fine Mg3RE particles; (c) HAADF-STEM image and EDXS-Mappings of Mg3RE phase variants.

Fig. 7. (a) HAADF-STEM image and EDXS-Mappings of spot Mg3RE particles; (b and c) Electron microdiffraction patterns of spot Mg3RE particles.

Fig. 8. HAADF-STEM images and corresponding FFT patterns show the typical ${{\beta }_{1R}}$ phase precipitates in the studied alloy: (a-c) general view in the $[11\bar{2}0]_{α}$ orientation and (d-h) general view in the [0001]α orientation; (d) HAADF-STEM image and EDXS mapping results of ${{\beta }_{1R}}$ phase in the [0001]α orientation; (g and h) details of ${{\beta }_{1R}}$ phase in the [0001]α orientation.

Fig. 9. BF-TEM images of the as-extruded alloy deformed to a total strain of 2% at (a) 25 °C and (b) 200 °C. B//$[11\bar{2}0]_{α}$. Note that red arrows point to the basal dislocations, while the white arrows point to the non-basal dislocations.

Fig. 10. BF-TEM images under two-beam conditions of the as-extruded alloy deformed to a total strain of 2% at (a-c) 25 °C and (d-f) 200 °C. Note that red arrows point to the non-basal <c+a> dislocations, black arrows point to the basal <a> dislocations, and blue arrows point to the non-basal <a> dislocations.

Fig. 11. Tensile stress-strain curves of as-extruded GLWZ8431 alloy at 25 °C, 150 °C and 200 °C.

Fig. 12. EBSD results of as-extruded GLWZ8431 alloy after tensile tests at (a, d and g) 25 °C, (b, e and h) 150 °C and (c, f and i) 200 °C. (a-c) IPF map; (d-f) Grain boundary map;(g-i) Twin map. Note that ETs refers to the extension twins, CTs refers to the contraction twins and STs refers to the secondary twins.

Fig. 13. Fracture surfaces of as-extruded alloy after tensile tests at (a) 25 °C, (b) 150 °C and (c) 200 °C. Note that the white arrows refer to bulk Mg3RE particles, while the black arrows refer to cracks.

Fig. 14. (a) OM image and (b-d) HAADF-STEM images show the microstructures at the bottom of the extruded ingot in the [0001]α orientation.

Fig. 15. CRSS increment of slip systems due to Orowan strengthening by ${{\beta }_{1R}}$ phase. The five slip systems are represented by different colors of markers.