A deformation mechanism based crystal plasticity model of ultrafine-grained/nanocrystalline FCC polycrystals

A new crystal plasticity model based on the deformation mechanism for ultrafine-grained/nanocrystalline face-centered cubic (FCC) metals was developed. The deformation mechanism was that dislocations glide from grain boundary to grain boundary (GB). Constitutive equations on the slip system level were developed based on dislocation glide and all stages of dislocation activities were considered especially their interactions with GB. An Arrhenius type rate equation was established based on the thermally activated depinning of dislocations from GB obstacles. The new constitutive equations were incorporated into a 3D crystal plasticity formulation, and this crystal plasticity model was implemented into a UMAT subroutine of the ABAQUS finite element program. The uniaxial deformation responses of the two ufg/nc materials were simulated. Crystal plasticity finite element method (CPFEM) simulations gave flow stress predictions that were very close to the experimental results. The dislocation mechanism-based crystal plasticity UMAT is ready to be used for more advanced simulation studies.