Evaluation of the twinning behavior of polycrystalline magnesium at room temperature by acoustic emission

In order to study the twinning behavior of polycrystalline magnesium at room temperature, acoustic emission (AE) was measured during the compression process at an intermediate strain rate along the extrusion direction. Microstructure evolution was quantitatively characterized by the twinning area fraction and the strain dependence of twinning size distribution from the observation by optical microscope. Deformation was mainly due to twinning nucleation in the initial stage, and twinning growth and dislocation motions gradually became dominant with the increase of strain. As AE count rate increased greatly in the initial stage of deformation and dropped quickly in the later stage, AE signals in the initial stage were thought to be mainly due to the twinning nucleation. Twinning strain and the fraction of twinning strain rate were calculated by considering the variation of Schmid factor in deformation. A quantitative relation between the twinning strain and the cumulative AE counts was obtained in the initial stage of deformation.