Using misorientation and weighted Burgers vector statistics to
understand the intragranular boundary development and grain boundary
formation at high temperatures
Abstract
Strain weakening during plastic deformation can be achieved via strain
energy reduction due to intragranular boundary development and grain
boundary formation. To examine intragranular boundary formation at high
temperatures (Th≈0.9), we analysed electron backscatter
diffraction (EBSD) data of coarse-grained ice deformed at -30°C.
Misorientation and weighted Burgers vector (WBV) statistics were
calculated along planar intragranular boundaries. Neighbour-pair and
random-pair misorientation distributions intersect at misorientation
angles of 10–30°, indicating an upper limit to the misorientation
threshold angle at which neighbouring grains begin to interact, e.g.,
rotate relative to each other. Misorientation angles change markedly
along each analysed intragranular boundary, linking low-
(<10°) and high-angle (10–38°) segments, with each segment
exhibiting distinct misorientation axes and WBV directions. We suggest
that these boundaries might be produced by the growth and intersection
of individual boundary segments comprised of dislocations with distinct
slip systems. This new kinematic model does not require a change in the
boundary geometry after its formation, as required by the other models,
to modify the crystallographic geometry of a planar boundary.
Misorientation axis distributions are fundamentally different between
intragranular boundaries (mostly confined to the ice basal plane) and
grain boundaries (largely dispersed). This observation suggests a strong
crystallographic control of intragranular boundary development via
subgrain rotation. The apparent lack of crystallographic control for
grain boundaries, on the other hand, suggests that misorientation axes
become randomized upon grain boundary formation, likely due to the
operation of other mechanisms/processes that can modify misorientation
axes.