The fracture toughness of molybdenum at different grain sizes under and since brittle-ductile transition: computer modeling and experiment

The sharp growth of the fracture toughness after brittle-ductile transition happens at grain sizes approximately equal to the plastic zone size. Here we analyze the influence of the grain boundary on the evolution of the ensemble of dislocations near the crack tip using dislocation dynamics method. We show evidence that for large grain sizes, the size has little effect on the ensemble of dislocations and the fracture toughness, but when dislocations reach the grain boundary, distribution of dislocations changes, which leads to increase of the fracture toughness.