A geometrical model for grain boundary migration mediated formation of multifold twins

• We successfully achieved in situ observation of the formation of grain boundary-mediated multifold twins. • Multifold twins can form by grain boundary migration associated with grain boundary splitting-related twinning processes. • The geometrical requirement for the formation of multifold twins was revealed by proposing a general geometrical model, which showed a strong dependence on twin boundary polarity (orientation) and matrix...