Fig. 1 Bi-crystal simulation model, in which the lower grain rotates 90° along the shared?<? a?>?direction with respect to the upper grain. The upper grain has a basal orientation with a horizontal c axis, while the lower grain has a prismatic orientation with a vertical c axis. Atoms are colored according to their coordination number to better visualize the grain boundary

Fig. 2 Migration of GB under uniaxial compression and tension. a1, b1 Initial interface; a2, b2 formation of a trapezoidal interface, which consists of CTB and BPB; a3, b3 GB migration with further expansion of the CTB and BPB

Fig. 3 a {10-12} CTB with a misorientation angle of 85°; b a general grain boundary consisting of both CTB and BPB. The misorientation angle of the latter is 90°

Fig. 4 Atomic process of interface migration. a-c Nucleation and glide of the interface steps on the BPB; d, e subsequent glide of twinning dislocations on the CTB

Fig. 5 Compressive a, tensile b stress-strain curves of Ti bi-crystals at different temperatures

Fig. 6 a Phase transformation from hcp to bcc under compressive loading. (b-d) Specific regions showing the orientation relationship. The dashed squares in b corresponding with subfigures c, d