Localised de-twining in AZ31 Mg alloy sheet during uniaxial compression deformation

A novel finding of this study is that localised de-twining caused by shear banding induced by uniaxial compression deformation was first found through in situ EBSD observation. The twinning deformation process showed in this paper consists of the following three steps: twinning, de-twinning and re-twinning, which needs more energy and larger load than the process of twin growth and coalescence and complete consumption. It is believed that localised de-twining deformation mechanism is one of the strengthening mechanisms in magnesium alloy. More interestingly, twinning and de-twinning deformation operate simultaneously in a single twinning system, which was not in good agreement with the prediction of previous reports [1]. It is the first time that such unusual deformation mechanism has been found in experimental results. According to the results and combining with theoretical analysis, uncertain local stress states in individual grains is the cause of unusual experimental phenomena. The back stress induced in a twin by the surrounding matrix plays an important role in localised de-twining during uniaxial compression.