  When a metal is loaded mechanically at high temperatures, i.e. above 300
$^o$C, its grain microstructure evolves due to multiple physical mechanisms.
Two of which are the curvature-driven migration of the grain boundaries due to
increased mobility, and the formation of subgrains due to severe plastic
deformation. Similar phenomena are observed during heat treatment subsequent to
severe plastic deformation. Grain boundary migration and plastic deformation
simultaneously change the lattice orientation at any given material point,
which is challenging to simulate consistently. The majority of existing
simulation approaches tackle this problem by applying separate, specialized
models for mechanical deformation and grain boundary migration sequentially.
Significant progress was made recognizing that the Cosserat continuum
represents an ideal framework for the coupling between different mechanisms
causing lattice reorientation, since rotations are native degrees of freedom in
this setting.
  In this work we propose and implement a multi-physics model, which couples
Cosserat crystal plasticity to Henry-Mellenthin-Plapp (HMP) type orientation
phase-field in a single thermodynamically consistent framework for
microstructure evolution. Compared to models based on the
Kobayashi-Warren-Carter (KWC) phase-field, the HMP formulation removes the
nonphysical term linear in the gradient of orientation from the free energy
density, thus eliminating long-range interactions between grain boundaries.
Further, HMP orientation phase field can handle inclination-dependent grain
boundary energies. We evaluate the model's predictions and numerical
performance within a two-dimensional finite element framework, and compare it
to a previously published results based on KWC phase-field coupled with
Cosserat mechanics.
