Macro- and microtexture evolution of an extruded Mg–Mn–Ce alloy during annealing

This study investigates the effect of high temperature heat treatments between 475°C and 550°C on the texture and microstructure evolution of an extruded ME21 magnesium alloy via in-situ time-of-flight neutron diffraction and EBSD. The neutron diffraction analysis reveals a significant impact of the temperature on the kinetics of the texture evolution, while the annealing textures are qualitatively similar to rare earth extrusion textures. Through EBSD analysis it was shown that an annealing temperature below 500°C generates a bimodal microstructure via abnormal grain growth featuring significant differences in grain size, where coarse grains are surrounded by finer grains. Abnormal grain growth initiates at sites, where substructured grains, high internal misorientations and large preexisting grains act together. Annealing temperatures above 525°C result in an accelerated grain growth forming a homogeneous microstructure. Although short term heat treatments generate textures favoring 〈a〉 basal slip for deformation along the extrusion direction, the compression failure strain was increased to a lower extent than using long term heat treatments.