Characterization of ultrafine and nano grained magnesium alloy processed by severe plastic deformation

Abstract

A wrought AZ31 magnesium alloy was severely deformed through a novel continuous severe plastic deformation technique, called accumulative back extrusion. The microstructure and texture obtained after applying multiple deformation passes at a temperature range of 80–380°C were characterized. After a single pass at 80°C an ultrafine/nano grained microstructure was obtained, while the initial texture was completely replaced by a new fiber basal texture, 40° inclined to transverse direction. As the processing temperature increased, the obtained texture intensities were strengthened, though the c-axis of crystals gradually rotated towards transverse direction and a <10–11> fiber texture parallel to normal direction was developed. Moreover, repetitive accumulative back extrusion was associated with tendency of basal plane to lie parallel to transverse direction, while the orientation of prismatic planes showed a random distribution around normal direction. After eight passes the most noticeable texture included fiber basal texture oriented almost parallel to the transverse direction, and <10–10> perpendicular to the extrusion direction and <10–11> parallel to the normal direction. The maximum texture intensity was decreased as the number of passes increased, which is attributed to strain path change involved during each consecutive accumulative back extrusion pass as well as promoted contribution of non-basal slip systems.