In order to study the twinning behavior of polycrystalline Mg at room temperature, acoustic emission was measured during the compression process at an intermediate strain rate along the extrusion direction. The microstructural evolution was quantitatively characterized by the twinning area-fraction and the strain-dependence of the twinning-size distribution using optical microscopy. The deformation was due mainly to twin nucleation in the initial stages, while twin-growth and dislocation motion gradually became dominant with increasing strain. As the acoustic emission count-rate increased greatly in the initial stages of deformation, and fell quickly in the later stages, the acoustic emission signals in the initial stages were thought to be due mainly to the twin nucleation. The twinning strain and the fraction of twinning strain-rate were calculated by considering the variation of the Schmid factor during deformation. A quantitative relationship between the twinning strain and the cumulative acoustic emission counts was obtained in the initial stages of deformation.

Evaluation of the Twinning Behavior of Polycrystalline Magnesium at Room Temperature by Acoustic Emission. Y.Li, M.Enoki: Materials Transactions, 2007, 48[6], 1215-20