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Abstract

Grain boundaries play an important role during plastic deformation and failure of poly-crystals. The presence of point defects, line defects or segregated second phase particles at the grain boundaries affect their mechanical properties, which in turn alter the hardness or fracture toughness of the poly-crystals favorably or adversely. In case of the bcc transition metals, which are the materials of interest for high temperature applications, grain boundaries and segregated impurities at grain boundaries play a vital role as well. Therefore, a Σ-5 (310)[001] Σ5 STGB present in molybdenum (Mo) has been atomistically investigated and the results are being used for fracture prediction at continuum scale.

The atomistic calculations were performed using the VASP employing GGA to DFT. After the initial convergence tests for the optimization of k-point meshing and energy cut-off of the plane wave basis set, a Σ5 (310)[001] STGB structure was constructed, relaxed and stable translation states along [310], [-130] and [001] were obtained. With this model uni-axial tests loaded perpendicular to the grain boundary plane having different C contents were performed. From these results, traction separation data has been derived that is being used for the parameterization of cohesive zone model to predict fracture of Mo bicrystals at continuum level using finite element analysis.