On the Swift effect and twinning in a rolled magnesium alloy under free-end torsion

We experimentally and numerically study the large-strain free-end torsion of a rolled magnesium alloy. It is found that a torsion sample with its axial direction parallel to the normal direction elongates axially, while a sample with its axial direction along the rolling direction contracts axially. It is shown that this Swift effect, i.e., the second-order axial effect under free-end torsion, is mainly due to extension twinning.