Fig. 1. SEM image (a) and XRD pattern (b) of as-received Ti-42.9Al-4.6Nb-2Cr.

Fig. 2. BF TEM images in γ grains when Ti-42.9Al-4.6Nb-2Cr with duplex structure isothermally compressed at : (a) 1200 ℃, 0.01 s-1, 20 %, (b) 1200 ℃, 0.01 s-1, 30 %, (c)-(f) 1200 ℃, 0.01 s-1, 40 %, (g) 1200 ℃, 0.01 s-1, 50 %, (inserts are magnifications of dotted boxes or SAED patterns of circles). (e) and (f) are similar TEM images by using different diffraction vectors.

Fig. 3. BF TEM images of isothermally compressed Ti-42.9Al-4.6Nb-2Cr with duplex structure: (a) 1200 ℃,1.0 s-1, 50 %, (c) 1200 ℃, 0.001 s-1, 50 %. (b) corresponding SAED pattern of the circle in (a).

Fig. 4. (a) Faults pairs on the right evolved into twins on the left in HRTEM image of Ti-42.9Al-4.6Nb-2Cr with duplex structure at 1200 ℃, 0.01 s-1, 50 %, (b)-(e) FFT images of (a), area R1, R2 and R3, respectively. Black arrows in (a) present the growth directions of faults.

Fig. 5. (a) Faults deflection, (b) faults deflection and rigid-body shuffling, (d) faults undeflected transmission in γ grains at 1200 ℃, 0.01 s-1, 50 %, inserts are the corresponding FFT images. (c) corresponding FFT image of (b).

Fig. 6. Three intersections modes in γ grains (Δd represents the rigid-body offset).

Fig. 7. (a) Shear bands in γ grains at 1150 ℃, 0.001 s-1, 50 %. (b) is the magnification of the dotted box in (a). The presence of shear bands implies large stress heterogeneity in γ grains.

Fig. 8. Illustration about the formation of twins in γ grains.

Fig. 9. Schematic illustration of twin intersections in γ grains. To simply for illustration, the intersection angle in the figures is changed from ～70° to 90°, and the change has no effect on elucidating twin intersections. (a) the initial stage of twin intersections. (b) the evolution of faults colored in yellow, resulting in the motion of intersection points A and B. (c) and (d) the following evolutions of faults colored in blue, causing two motion modes of intersection points C and D. The twin intersections modes are depended to twin growth directions.