Fig. 1. Engineering stress-strain curves of solid solution treated (ST) sample and solid solution treatment plus aging (STA) sample: (a) overall stress-strain curve; (b) close-up image of dash line area in (a) to show the elastic region.

Fig. 2. Microstructures of the alloy after ST and STA heat treatment: (a) solid solution treated at 800 ℃; (b) solid solution treated at 800 ℃ followed by 570 ℃/6 h aging.

Fig. 3. Bi-modal structures of Ti-5Al-4Zr-8Mo-7 V alloy after 800 ℃ solution treatment and 570 ℃ aging: (a) overall image shows primary α (αp), fine and coarse secondary α (αs); (b, c) the detailed substructures of coarse and fine αs with SAED pattern inserted, respectively.

Fig. 4. Composition of Al and Mo in α phase and β matrix: (a) distribution of Al, Mo in αp and β matrix; (b) Al, Mo in lamella αs and β matrix.

Fig. 5. Dislocations in β matrix at ε = 0.03 after 800 ℃ solid solution treatment: (a) B ≈ [001], g=[010]; (b) B ≈ [001], g=[$\bar{11}$ 0].

Fig. 6. Dislocation morphologies in β matrix at 8% tensile strain: (a) B ≈ [$\bar{1}$ 11], g=[$\bar{11}$ 0]; (b) B ≈ [$\bar{1}$ 11], g=[$\bar{11}$ 0].

Fig. 7. Dislocation morphology in β matrix at 20 % tensile strain: (a) B ≈ [00 1], g=[100]; (b) close-up image of (a).

Fig. 8. Wavy slip in transformed β phase of 570 ℃ aged Bi-modal structure with 3% strain: (a) B ≈ [$\bar{1}$ 22], g=[01 $\bar{1}$]; (b) detailed dislocation configuration under g=[01 $\bar{1}$].

Fig. 9. Dislocation configurations in transformed β phase of 570 ℃ aged Bi-modal structure with 10 % strain: (a) B ≈ [013], g=[200]; (b) different region under B ≈ [013], g=[200].

Fig. 10. Plastic deformation in globular αp with 3% strain under different g: (a) B ≈ [1 $\bar{2}$ 1 $\bar{3}$], g=[0 $\bar{1}$ 11]; (b) B ≈ [1 $\bar{2}$ 1 $\bar{3}$], g=[1 $\bar{1}$ 01]; (c) high dislocation density at αp edge; (d) low dislocation density in the center of αp.

Fig. 11. Dislocation morphology in globular αp with 8% strain under different operation vector g. (a), (b) and (c) is under g=[$\bar{1}$ 011] with electron beam B ≈ [01 $\bar{1}$ 1]; (d), (e) and (f) is under g=[0001] under B ≈ [01 $\bar{1}$ 0]. (b), (e) and (c), (f) display the dislocation morphologies of edge and center region in αp, respectively.

Fig. 12. Plastic deformation of globular αp after tensile test under g=[$\bar{1}$ 011], B ≈ [01 $\bar{1}$ 1]: (a) core-shell structure of αp; (b) dislocation morphology in the hard shell area; (c) dislocation in the soft core area.