Grain-Boundary Effects and Failure Mechanisms in Crystalline Materials

The major objective of the present study has been to determine the influence of high angle grain boundary orientations on the failure of metallic face-centered cubic (f.c.c.) crystals. An investigation of the coupled effects of grain boundary misorientation, dislocation densities, strain hardening, and geometrical softening on failure evolution in crystalline materials has been conducted. The constitutive formulation has been based on a crystalline plasticity multiple-slip formulation, where the flow stresses have been coupled to the dislocation densities in each grain. Results from the present analysis and comparisons with experimental studies indicate that ductile and brittle failure mechanisms can be characterized in terms of the material competition between the strengthening and the softening mechanisms of the crystalline structure.