| Conventional face centered cubic (fcc) metals do not exhibit a ductile-to-brittle transition because spontaneous dislocation emission from the crack tips in these materials inhibits the stresses to be raised high enough for breaking atomic bonds, i.e. brittle fracture. The results of tensile testing of fcc nanolayered and nanocrystalline metals suggest that when the microstructural length scale is reduced to nanoregime cleavage fracture becomes possible in these materials. It is also shown that the stress-state, similar to bcc (body-centered-cubic) metals, affects the fracture behavior considerably. These observations are discussed in terms of the development of internal stresses during the deformation of metallic nanostructures. |
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