101¯1 twin boundary showing very large deviation from the theoretical one in deformed magnesium alloy

Structure of 101¯1 twin boundary in an AZ31 magnesium alloy has been characterized by means of transmission electron microscopy (TEM) and high-resolution TEM. It is found that actual twin boundary entirely departs from theoretical twinning plane in 101¯1 twin system. Furthermore, it is shown that six kinds of facets, including 101¯1 coherent twin boundaries, {0002}‖101¯1¯ basal-pyramidal (BPy), 1¯011¯‖{0002} pyramidal-basal (PyB), 1¯010‖101¯3 prismatic-third pyramidal (P3Py), basal-prismatic (BP/PB) boundaries and 101¯2 coherent twin boundaries, can coexist in one 101¯1 twin system. Based on these structure features, the underling mechanisms responsible for large deviation phenomenon are discussed, with focus on BPy, PyB, P3Py boundaries and strain accommodation.