{10 (1) over bar2} twinning occurs extensively in Mg to accommodate plastic deformation. With multiple active twin variants, twin-twin interaction occurs and this often forms twin-twin boundaries. In this work, the {11 (2) over bar2} twin-twin boundary is studied using electron backscatter diffraction (EBSD) analysis and atomistic simulations. EBSD data show that many of the twin-twin boundaries align well with {11 (2) over bar2} or {11 (2) over bar6} planes. Further, atomistic simulations reveal dynamically the formation of {11 (2) over bar2} boundary via the interaction of two non-cozone {10 (1) over bar2} twin variants. Moreover, the twinning mode of the {11 (2) over bar2} boundary is found to be an extension twin with second undistorted plane of {11 (2) over bar6}. In addition, the {11 (2) over bar2} boundaries contribute significantly to the 60 degrees < 01 (1) over bar0 > peak in the misorientation histogram; they also play an essential role in the unique strong strain hardening under c-axis tension. Our findings are crucial for completing the twinning theories for Mg.
NSTL
Elsevier