Abstract: Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is investigated. Active ${11\bar{2}1}$ and ${10\bar{1}2}$ extension twinning is observed. The activation of ${11\bar{2}1}$ twinning in a certain grain is influenced not only by its own Schmid factor, but also by that of the basal slip. Twin-twin interactions of the co-zone ${11\bar{2}1}$ twin variants are commonly observed and systematically studied, including the crystallographic characteristics of the four typically observed twin-twin junctions (TTJs) and the associated twin-twin boundaries. Unlike the quilted-looking TTJs formed by the interaction of co-zone ${10\bar{1}2}$ twin variants, crossing-like TTJs of co-zone ${11\bar{2}1}$ twin variants are observed and their formation mechanisms are discussed. Crossing-like TTJs are also formed by the interaction of ${11\bar{2}1}$ and ${10\bar{1}2}$ twins. The morphology and thickening rate of ${11\bar{2}1}$ and ${10\bar{1}2}$ twins vary markedly due to the difference in twinning shear. The needle-like ${11\bar{2}1}$ twins thicken more slowly than the lenticular ${10\bar{1}2}$ twins. Twin nucleation is observed on the previously formed ${11\bar{2}1}$ twin boundary due to the relatively large strain concentration on such interface, while twin nucleation on ${10\bar{1}2}$ twin boundary is rarely observed.

Key words: Mg alloy, Plastic deformation, Twinning, Twin-twin interaction, Twin-twin junction