On the long-term correlations in the twinning and dislocation slip dynamics

Abstract

The present work aims at gaining new insights into the dynamics of the dislocation slip and twinning processes, which govern the majority of possible scenarios of plastic deformation in structural metals and alloys. Using model magnesium single crystals and employing the statistical analysis of acoustic emissions (AE) generated in the course of plastic deformation, it was demonstrated that twinning is a process with a memory of the past whereby the twinning events affect the occurrence of successive events. As opposes to this, the basal dislocation slip appears as a substantially random intermittent process comprising of independent elementary slip events without long-term correlations between gliding dislocations or slip bands emerging due to the collective dislocation glide along basal planes. The single crystals were chosen with axial orientations best suitable to facilitate either basal dislocation slip or tensile twinning under compressive loading, which significantly simplified the interpretations of AE findings. Besides, the AE results were fully corroborated in situ by microstructure observations using scanning electron microscopy imaging.