grain boundary energy and strengths: values in the literature

• Qiao & Kong (2004) 25kJ/m work of separation of grain boundary, includes plastic dissipation.  Note units; this is per unit length grain boundary not per unit area of crack surface (or even per unit area of grain boundary).  This is used to compute the total fracture work to cross the grain boundary; 25 kJ/m * (persistent area per unit length grain boundary) = (units of kJ)
• Stec & Faleskog (2009) take the work of separation (excluding plastic deformation) to be 640 N/m in general.  Here the units are N/m = J/m^2 as necessary for their cohesive model applied to the grain boundary. They also employed values of Gamma_GB = 160, 320, & 1600 N/m.
• Stec & Faleskog (2009) cite the ideal ferrite strength = 12 GPa, but use sigma_max = 4.8 GPa to account for material defects and dissipation effects.