High temperature deformation and recrystallization behavior of magnesium bicrystals with 90° and 90° tilt grain boundaries
在线提供 19 October 2023
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Kevin Bissa, Talal Al-Samman, Dmitri A. Molodov
Abstract
The deformation mechanisms and dynamic recrystallization (DRX) behavior of specifically grown bicrystals with a symmetric 90° and 90° tilt grain boundary, respectively, were investigated under deformation
in plane strain compression at 200 °C and 400 °C. The microstructures
were analyzed by panoramic optical microscopy and large-area electron
backscatter diffraction (EBSD) orientation mapping. The analysis
employed a meticulous approach utilizing hundreds of individual, small
EBSD maps with a small step size that were stitched together to provide
comprehensive access to orientation and misorientation data on a
macroscopic scale. Basal slip primarily governed the early stages of
deformation at the two temperatures, and the resulting shear induced
lattice rotation around the transverse direction (TD) of the sample. The
existence of the grain boundary gave rise to dislocation pile-up in its
vicinity, leading to much larger TD-lattice rotations within the
boundary region compared to the bulk. With increasing temperature, the
deformation was generally more uniform towards the bulk due to enhanced
dislocation mobility and more uniform stress distribution. Dynamic
recrystallization at 200 °C was initiated in -compression
twins at strains of 40% and higher. At 400 °C, DRX consumed the entire
grain boundary region and gradually replaced the deformed microstructure
with progressing deformation. The recrystallized grains displayed
characteristic orientations, such that their c-axes were perpendicular
to the TD and additionally scattered between 0° and 60° from the loading
axis. These recrystallized grains displayed mutual rotations of up to
30° around the c-axes of the initial grains, forming a discernible basal
fiber texture component, prominently visible in the pole figure. It is noteworthy that the deformation and DRX behaviors of
the two analyzed bicrystals exhibited marginal variations in response
to strain and deformation temperature