Grain boundary interface mechanics in strain gradient crystal plasticity

Interactions between dislocations and grain boundaries play an important role in the plastic deformation of polycrystalline metals. Capturing accurately the behaviour of these internal interfaces is particularly important for applications where the relative grain boundary fraction is significant, such as ultra fine-grained metals, thin films and microdevices. Incorporating these micro-scale interactions (which are sensitive to a number of dislocation, interface and crystallographic parameters) within a macro-scale crystal plasticity model poses a challenge. The innovative features in the present paper include (i) the formulation of a thermodynamically consistent grain boundary interface model within a microstructurally motivated strain gradient crystal plasticity framework, (ii) the presence of intra-grain slip system coupling through a microstructurally derived internal stress, (iii) the incorporation of inter-grain slip system coupling via an interface energy accounting for both the magnitude and direction of contributions to the residual defect from all slip systems in the two neighbouring grains, and (iv) the numerical implementation of the grain boundary model to directly investigate the influence of the interface constitutive parameters on plastic deformation. The model problem of a bicrystal deforming in plane strain is analysed. The influence of dissipative and energetic interface hardening, grain misorientation, asymmetry in the grain orientations and the grain size are systematically investigated. In each case, the crystal response is compared with reference calculations with grain boundaries that are either 'microhard' (impenetrable to dislocations) or 'microfree' (an infinite dislocation sink). © 2013 Elsevier Ltd. All rights reserved

Grain boundary interfacial plasticity with incorporation of internal structure and energy

Modelling the behaviour of grain boundaries in polycrystalline metals using macroscopic continuum frameworks demands a multi-scale description of the underlying details of the structure and energy of grain boundaries. The objective in this work is the incorporation of a multi-scale atomistic-to-continuum approach of the initial grain boundary structure and energy into a grain boundary extended crystal plasticity framework in order to investigate the role of the grain boundary energetics on the macroscopic response. To this end, the methodology includes: (i) the generalisation of the atomistic-to-continuum results of the initial grain boundary structure and energy, (ii) an analytical analysis of the resulting grain boundary energetics in the continuum framework, (iii) the numerical implementation of the developed framework in the case of a periodic bicrystal subjected to simple shear deformation considering a symmetric tilt boundary system in the full misorientation range. This work provides a step forward towards the physically based continuum modelling of grain boundary interfacial plasticity