Fig. 1. SEM forging microstructure of the present received Ti-5553 alloy.

Fig. 2. Band contrast and IPF (inverse pole figure) orientation images of three IMs: (a) single β; (b) clavate α; (c) lamellar α.

Fig. 3. Stress-strain curves of the three IMs under strain rate of 0.001s-1: (a) overview; (b) initial yield region in (a) magnified.

Fig. 4. Work hardening rates (derivative of the true stress-true strain curves, dσ/dε) plotted as a function of the true strain, dε, for three IMs deformed under 0.001 s-1. The yellow dotted line represents dσ/dε = 0.

Fig. 5. Stress-strain curves of single β IM under the strain rate of 0.001s-1: (a) overview; (b) typical discontinuous yield behavior at 800 °C and 900 °C in (a) magnified.

Fig. 6. Stress-strain curves of the single β IMs at 600 °C: (a) overview; (b) initial yield region in (a) magnified.

Fig. 7. SEM images of the single β IM warm compressed at 600 °C to 0.7 at 0.001s-1: (a, b) obvious single- and multi-slip bands in β phase matrix; (c, d) larger magnification images of single- and multi-slip bands.

Fig. 8. SEM images of the single β IM warm compressed at 600 °C to 0.7 at 0.001s-1: (a, b) microstructure of different regions; (c, d) shear fracture in the lamellar α constituents.

Fig. 9. SEM images of the clavate α IM warm compressed at 600 °C to 0.7 at 0.001s-1: (a) slip bands; (b) α rotation relative to the direction of vertical deformation; (c, d) αs in the residual β matrix.

Fig. 10. SEM images of the lamellar α IM warm compressed at 600 °C to 0.7 at 0.001s-1: (a, b) the distortion of the lamellar α; (c, d) αs in the residual β matrix.

Fig. 11. SEM images of the single β IM warm compressed microstructure before, during and after yielding at 600 °C and 0.001s-1: (a) elastic deformation stage; (b) in the process of yielding; (c) after yielding. The sampling points a, b and c are marked in the stress-strain curves.

Fig. 12. Micrographs of the alloy warm compressed at 600 °C to 0.04 at 0.001s-1: (a) clavate α; (b) lamellar α.

Fig. 13. (a) SEM images of the clavate α IM warm compressed at 600 °C to 0.7 at 0.001s-1 (b) {110}, {112} and {123} pole figures of the β matrix in (a). The Schmidt factor values under the compression are indicated for each slip system. (c) The slip crystallographic schematic in the single β grain (Euler angles, (36.2°, 12.0°, 15.5°)) respect to the compressive loading.

Fig. 14. Representative TEM micrographs and SAED patterns of three different IMs warm compressed at 600 °C to 0.04 at 0.001s-1: (a-c) single β; (d-f) clavate α; (g-i) lamellar α.

Fig. 15. Crystal plasticity finite element simulations of three different IMs warm compressed at 600 °C to 0.04 at 0.001s-1: (a) single β; (b) clavate α; (c) lamellar α. (a2, b2, c2) mises stress; (a3, b3, c3) equivalent plastic strain; (a4, b4, c4) geometrically necessary dislocation.

Fig. 16. Four main deformation stages during the hot compression tests (example, single β IM compressed at 600 °C to 0.7 with 0.001s-1): (Ⅰ) Elastic-elastic (elastic); (Ⅱ-Ⅲ) Elastic-plastic (work-hardening); (Ⅱ) Slip bands forming; (Ⅳ) Plastic-plastic (softening).

Fig. 17. Photographs of the macroscopic deformation characteristics of the single β IM compressed at: (a) 600 °C, 0.7, 0.001s-1; (b) 600 °C, 0.7, 0.01s-1.