Low-temperature severe plastic deformation of pure magnesium

Abstract

In this paper, the microstructure and texture of pure magnesium after rolling at low temperatures have been investigated. Pre-deformed magnesium in the form of a plate with the thickness of 1 mm was rolled at room and cryogenic temperatures down to foils with 150 µm thickness. The true strain was ε ~1.9. Methods of X-ray diffraction, scanning electron microscopy with electron backscattering diffraction analyses (EBSD-analysis) and transmission electron microscopy have been used to investigate the structure and texture of the magnesium foils. In the initial state, the plate has a weakened basal texture and fine-grained structure. It was shown that the basal texture (0001) became stronger during rolling regardless of the deformation temperature. In all cases, the structure was heterogenic and consisted of large recrystallized grains with preferred basal orientation and smaller (sub)grains. However, it was noted that the room-temperature rolling led to an increase of the fraction of large grains, and lower deformation temperature prevents an active grain growth. The change of the number fraction of low-angle and high-angle boundaries could point on different lead mechanisms during deformation. At room-temperature rolling, there is the predominance of slip processes and dynamic recrystallization. As for at cryo-deformation, the twinning is more active and the dislocation slip could be suppressed for a while.