Molecular dynamic simulation was used to study the brittle versus ductile fracture behaviour in nanotwinned Ni at various temperatures. The simulation results show that three temperature regimes correspond to three different fracture behaviours: brittle, brittle-to-ductile transition and ductile. A dual fracture transition mechanism in nanotwinned Ni within a small temperature interval was observed: (1) local phase transformation and (2) ledge formation ahead of the crack tip induced a sharp fracture transition from brittle mode to ductile mode. Our simulation results reveal that the very rare double fracture transition mechanisms could be transformed quickly in nanotwinned Ni within a narrow temperature interval, suggesting a new interpretation of fracture and deformation of nanotwinned Face Centred Cubic metals.
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