Analysis of deformation mechanisms in a textured AZ31 magnesium alloy

Abstract

A combination of advanced in-situ and ex-situ methods providing complementary information was employed in order to reveal the active deformation mechanisms during deformation of a heavily textured commercial magnesium alloy AZ31. Three sets of samples for both compression and tension testing were prepared from the rolled sheet with respect to its identified strong basal texture – normal direction (ND), rolling direction (RD) and 45° between RD and ND. During both compressive and tensile deformation of these samples, the signal of acoustic emission (AE) was concurrently measured. Afterwards, electron backscattered diffraction (EBSD) was used to study the microstructure after the selected stages of deformation. The EBSD analysis revealed that in the samples favourably oriented for extension twinning it played an important role during the plastic deformation, whereas its role in the unfavourably oriented samples was minor. This orientation and deformation mode dependency of extension twinning activation resulted in considerable differences in the deformation behaviour, which also influenced the AE response. A consistent link between the AE signal and the microstructural changes investigated by EBSD was established. Furthermore, to study the dynamics of plastic deformation and twin growth, high-speed camera footage of the sample surface was captured during compressive deformation. The obtained results were in complete accordance with the predicted behaviour, thus providing direct proof of the theory and extending the understanding of the deformation mechanisms.