Fig. 1. (a) SEM-EBSD inverse pole figure (IPF) micrograph of the β solution-treated Ti-7333 alloy indicating the microstructure with equiaxed β grains; (b) TEM bright-field micrograph showing the distinct dislocation lines distributed within the β matrix (as highlighted by white arrows in Fig.1(b)) and the corresponding Selected Area Electron Diffraction (SAED) patterns with (b1) [101]β and (b2) [111]β zone axes, respectively, indicating only β phase detected after the β solution treatment.

Fig. 2. Micrographs of the β solution-treated Ti-7333 alloy after aging treatment at 500 °C for different times: (a) aging treatment for 2 min showing the formation of grain boundary α precipitates (b) aging treatment for 5 min showing the generation of the V-shaped or triangular clusters formed by orientated intragranular α precipitates with a lath-like morphology; (c) aging treatment for 15 min showing the formation widmanstätten α precipitates nearby grain boundaries.

Fig. 3. (a) The variation of volume factions of α precipitates and (b) the corresponding hardness of aging-treated Ti-7333 alloy during aging treatments.

Fig. 4. (a) TEM bright-field micrograph of the β solution-treated Ti-7333 alloy after aging treatment at 500 °C for 2 min showing intragranular α precipitates located nearby the dislocations, and the inset giving the corresponding SAED patterns with ${{[01\bar{1}]}_{\beta }}$ zone axis; (b) corresponding dark-field micrograph of intragranular α precipitates obtained using ${{(01\bar{1}0)}_{\alpha }}$ reflection as indicated by the red circle in the inset of Fig. 4(a).

Fig. 5. (a) TEM bright-field micrograph of the β solution-treated Ti-7333 alloy after aging treatment at 500 °C for 5 min showing that the V-shaped clusters located nearby dislocations and composed of two orientated lath-like intragranular α precipitates; (b) TEM bright-field micrograph of the alloy after aging treatment at 500 °C for 15 min showing that the V-shaped or triangular clusters composed of different orientated intragranular α precipitates.

Fig. 6. BSE micrographs of the β solution-treated Ti-7333 alloy after aging treatment for 3 h at different temperatures: (a) 450 °C; (b) 500 °C and (c) 550 °C.

Fig. 7. Crystallographic analyses of α precipitates of the β solution-treated Ti-7333 alloy after aging treatment for 5 min at 500 °C: (a) SEM-EBSD IPF micrograph showing a intragranular α precipitate; (b) {11 11 13}β pole figure of the β grain; (c) {110}β and <111>β pole figures of β grain; (d) {0001}α and $<11\bar{2}0>$ α pole figures of the intragranular α precipitate.

Fig. 8. Crystallographic analyses of α clusters of the β solution-treated Ti-7333 alloy after aging treatment at 500 °C for 5 min: (a) BSE micrograph showing the V-shaped or the triangular clusters composed of α variants; (b) BOR plane and directions pole figures of β grain; (c) BOR plane and directions pole figures of the V-shaped α cluster (as highlighted in the inset); (d) BOR plane and directions pole figures of the triangular α cluster (as highlighted in the inset).

Fig. 9. X-ray diffraction pattern of the β solution-treated Ti-7333 alloy after aging treatment at 550 °C for 5 min.

Fig. 10. Crystal defects analyses of the β solution-treated Ti-7333: (a) TEM bright-field micrograph showing the distinct dislocation lines distributed within β grains (as highlighted by red dotted lines) and the Kikuchi line patterns (the inset) indicating the orientation of the β grain; (b) corresponding <112>β pole figure of the β grain superimposed with the trace of dislocation lines as indicated in Fig.10(a).