The plastic flow localization effect on crystalline material

Irradiation affects the mechanical properties of materials. In particular, an increase of yield strength followed by a decrease of ductility and a reduction of the elongation to fracture are observed above a threshold irradiation dose. The last two phenomena are correlated with the appearance of bands free of defects (clear bands) in which plastic deformation is confined. These bands also determine accumulation of dislocations at grain boundaries, thereby favouring local grain decohesion and possibly initiating fracture. Clear bands have an important impact on metal resistance, nevertheless our level of understanding is not sufficient to evaluate quantitatively their effect on the loss of ductility and reduction of elongation to fracture that are observed experimentally. A clear band is a microstructural defect, created when loading an irradiated material. Its complex interaction with defects on the nanoscale affects the behaviour of the metal at the macroscopic scale. A full understanding implies the application of a multiscale modeling approach. This explains why, even though clear bands have first been observed in the 1960s, it is only in the last decade that a modeling effort has been started to model how they form and their effect on the plastic behaviour.