Transition of deformation and fracture behaviors in nanostructured face-centered-cubic metals

Tensile stress–strain curves demonstrate that single-phase nanocrystalline face-centered-cubic (fcc) metals are intrinsically ductile and their failure begins with necking. However, the area reductions and the fracture behaviors were found to be dependent on the grain size. When plastic deformation is governed by dislocation activity, the nanocrystalline samples behave similar to the conventional coarse-grained materials. As the grain size is reduced to the regime where grain boundary sliding dominates, the material shows very high strain-hardening rate and the tensile samples fail by microcracking with no noticeable reduction in area.