Dynamic recrystallization during high temperature deformation of magnesium

As a consequence of the high critical stresses required for the activation of non-basal slip systems, dynamic recrystallization plays a vital role in the deformation of magnesium, particularly at a deformation temperature of 200 degrees C, where a transition from brittle to ductile behavior is observed. Uniaxial compression tests were performed on an extruded commercial magnesium alloy AZ31 at different temperatures and strain rates to examine the influence of deformation conditions on the dynamic recrystallization (DRX) behavior and texture evolution. Furthermore, the role of the starting texture in the development of the final DRX grain size was investigated. The recrystallized grain size, measured at large strains (epsilon similar to -1.4) seemed to be more dependent on the deformation conditions than on the starting texture. In contrast to pure magnesium, AZ31 does not undergo grain growth at elevated deformation temperatures, i.e. 400 degrees C, even at a low strain rate of 10(-4) s(-1). Certain deformation conditions gave rise to a desired fully recrystallized microstructure with an average grain size of similar to 18 mu m and an almost random crystallographic texture. For samples deformed at 200 degrees C/10(-2) s(-1), optical microscopy revealed DRX inside of deformation twins, which was further investigated by EBSD. (c) 2008 Elsevier B.V. All rights reserved.