Fig. 1 Initial microstructures of Ti750s high-temperature titanium alloy prior to thermal compression: a low-magnification SEM morphology; b high-magnification SEM morphology; c EBSD IPF map and d corresponding reconstruction of the prior β grains. Three directions in the three-dimensional space are defined in the alloy plate, viz., the compression axis (CA), rolling direction (RD), and transverse direction (TD). The EBSD IPF legends are provided as well

Fig. 2 Elemental distribution characteristics of silicides, referring to all elements contained in the alloy

Fig. 3 Stress-strain curves of Ti750s alloy compressed at various elevated temperatures at three strain rates: a 920 °C, b 950 °C, c 980 °C, d 1010 °C, e 1040 °C, f 1070 °C

Fig. 4 Hot processing map of Ti750s high-temperature titanium alloy at various strains of a ε = 0.1; b ε = 0.3; c ε = 0.5 and d ε = 0.7. The contour numbers represent the power dissipation rate η, while the shadow area indicates the plastic unstable zone

Fig. 5 Division of various deformation regions in hot processing map of Ti750s alloy at a true strain of 0.7. Six distinct regions were highlighted by dotted-line rectangles for further microstructural investigation

Fig. 6 Microstructural characteristics of region I in the hot processing map in Fig. 5: a 920 °C/0.1 s−1 and b 950 °C/1 s−1. The insets schematically illustrate the samples for microstructural observations cut from the core positions of the compressed samples

Fig. 7 EBSD characteristics of Ti750s alloy compressed at the condition of 920 °C/0.1 s−1: a IPF map and b misorientation angle distribution. Three-dimensional space of the samples and legend for EBSD IPF map were provided as well

Fig. 8 EBSD IPF map of primary α phase in Ti750S alloy subjected to 950 °C/1 s−1. Four representative regions marked I, II, III and IV were chosen for further crystallographic analysis in Fig. 9

Fig. 9 Crystallographic orientation characteristics of primary α phase chose in Fig. 8 at various regions: a I, b II, c III and d IV

Fig. 10 Pole figure of Ti750s high-temperature titanium alloy deformed at 950 °C/1 s−1: a β phase and b α phase

Fig. 11 SEM microstructural morphologies of region II in Fig. 5 at various deformation conditions of: a 950 °C/0.1 s−1, b 980 °C/0.1 s−1. The insets schematically illustrate the samples for microstructural observations cut from the core positions of the compressed samples

Fig. 12 Crystallographic characteristics of β phase in Ti750s alloys deformed at 980 °C/0.1 s−1: a IPF-X map, b IPF-Y map, c IPF-Z map, and d corresponding pole figure

Fig. 13 SEM microstructural morphologies of region III in Fig. 5 at various deformation conditions of: a 920 °C/10 s−1 at the low magnification; b within core zone in a; c within dead zone in a; d 950 °C/10 s−1 at the low magnification; e within core zone in d; and f within dead zone in d. The insets schematically illustrate the samples for microstructural observations cut from the positions of the compressed samples

Fig. 14 EBSD characterizations of zone IV and the corresponding reconstruction of original β grains in Ti750s deformed at: a, b and c 1010 °C/1 s−1; d, e and f 1040 °C/1 s−1. a and d IPF maps. b and e Superimposed maps of original β grains and grain boundaries. c and f Only reconstructed original β grains

Fig. 15 EBSD characterizations of zone V and the corresponding reconstruction of original β grains in Ti750s deformed at: a, b and c 1040 °C/0.1 s−1; d, e and f 1070 °C/0.1 s−1. a and d IPF maps. b and e Superimposed maps of original β grains and grain boundaries. c and f Only reconstructed original β grains

Fig. 16 Grain orientation spread in β phase safety zone in Ti750s deformed at: a 1010 °C/1 s−1, b 1040 °C/1 s−1, c 1040 °C/0.1 s−1, and d 1070 °C/0.1 s−1

Fig. 17 Dynamic recrystallization in hot working safety zone at various deformation conditions of: a and b 1010 °C/1 s−1, c and d 1040 °C/0.1 s−1. a and c Showing continuous dynamic recrystallization, b and d indicating discontinuous dynamic recrystallization

Fig. 18 EBSD characterizations of zone VI and the corresponding reconstruction of original β grains in Ti750s deformed at: a, b and c 1010 °C/10 s−1; d, e and f 1040 °C/10 s−1. a and d IPF maps. b and e Superimposed maps of original β grains and grain boundaries. c and f Only reconstructed original β grains

Fig. 19 EBSD characterizations of zone VI and the corresponding reconstruction of original β grains in Ti750s deformed at: a, b and c 1010 °C/10 s−1; d, e and f 1040 °C/10 s−1. a and d IPF maps. b and e Superimposed maps of original β grains and grain boundaries. c and f Only reconstructed original β grains

Fig. 20 High-temperature deformation mechanism of Ti750s alloys within various processing areas. Microstructural characteristics in each area is schematically illustrated as well