{10(1)over-bar1} twin boundary showing very large deviation from the theoretical one in deformed magnesium alloy

Structure of {1011) 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 [10 (1) over bar1 twin system. Furthermore, it is shown that six kinds of facets, including [10 (1) over bar1 coherent twin boundaries, {0002}parallel to 10 (1) over bar(1) over bar} basal-pyramidal (BPy), (1) over bar0 (1) over bar(1) over bar)parallel to{0002} pyramidal-basal (PyB), {(1) over bar 010}parallel to{10 (1) over bar3} prismatic-third pyramidal (P3Py), basal-prismatic (BP/PB) boundaries and {10 (1) over bar2} coherent twin boundaries, can coexist in one {10 (1) over bar1) 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.