Revealing slip-induced extension twinning behaviors dominated by micro deformation in a magnesium alloy

In this study, an in situ SEM/EBSD study on slip-induced extension twinning (S→T) behaviors of a Mg–Y alloy was conducted. It shows that the S→T process cannot be well explained using the classical geometrical compatibility parameter (m') determined by macroscopic stress. A new experimental method is proposed to unequivocally determine the slip directions of the source slip systems by combining the lattice rotation analysis and the slip trace analysis. By using the experimentally determined active slip systems, the validity of m' to reveal the S→T mechanism is improved. By a detailed study on lattice rotations of the grains containing source slip for twinning, it is found that the S→T process is dominated by micro deformation instead of macro deformation. This study emphasizes the importance of considering the effect of microscopic deformation when attempting to understand the S→T process in deformed magnesium alloys. •Slip-induced extension twinning (S.→T) behaviors in a Mg–Y alloy were investigated by in situ SEM/EBSD.•Lattice rotation analysis showed that the S.→T process is dominated by micro deformation instead of macro deformation.•A new experimental method was proposed to unambiguously reveal the real source slip system in the S.→T process.•The validity of the classical geometrical compatibility parameter (m') to explain the S.→T mechanism was improved.