Fig. 1. (a) EBSB map of the grains containing multiple twin variants. Black lines and red lines are used to mark {11$\bar{2}$ 2} and {10$\bar{1}$ 2} twins. The G1-M1, G1-M2, M1-M2 and M2-G2 grain boundaries are highlighted by yellow, white, orange and green lines, respectively. (b) Crystallographic illustration of six {11$\bar{2}$2} twin variants. (c, d) Magnified EBSD maps showing typical twin-twin interaction structures. (e, f) Crystallographic illustrations of T2-T6 and T2-T4 twin-twin pairs with the intersection lines along [$\bar{2}$4$\bar{2}$3] and [$\overline{22}$43], respectively. (g) Schmid factors of six twinning variants in both M1 and M2 grains.

Fig. 2. (a) Bright field TEM image of {11$\bar{2}$ 2} twin-twin intersection. (b) SAED pattern of T6 twin boundary as marked by “b” in (a). (c) Crystallographic relationship of T6 and matrix, the blue and red crystal lattices stand for matrix and T6, respectively. (d) SAED pattern of T2 viewed from [$\overline{11}$2$\bar{3}$] zone axis of T2. (e) Crystallographic orientation of T2 and matrix viewed along [$\bar{1}$ 100] zone axis of matrix, the green crystal lattice stands for T2. (f) TEM bright field image of viewed from [$\overline{11}$ 2$\bar{3}$] zone axis of T2. (g, h) SAED patterns of T6’ and T6, respectively.

Fig. 3. (a) Bright field TEM image of a (112$\bar{2}$) twin. (b) SAED pattern of twin boundary highlighted by a red square in (a), showing the deviation angle for the twin lattice. (c) Filtered HRTEM image taken from the red square in (a), showing the lattice rotation by the highlighted (112$\bar{2}$) planes for matrix and twin.

Fig. 4. Schematics for the twin-twin interaction mechanism. (a) Nucleation of T6. (b) Nucleation of T2. (c) Interaction between T6 and T2. (d) De-twinning and lattice rotation of T6. (e) Illustration of Burgers vector directions for the dislocations before and after dissociation.