On the intrinsic ductility of electrodeposited nanocrystalline metals

While nanocrystalline materials hold promise for structural applications in which increased strength is beneficial, their adoption has been hindered by concerns over the achievable ductility, resulting largely from considerable data scatter in the literature. A statistically significant set of 147 electrodeposited nanocrystalline tensile specimens was used to investigate this topic, and it was found that while necking elongation obeys similar processing quality and geometrical dependencies as conventional engineering metals, the intrinsic ductility as measured by uniform plastic strain was unexpectedly independent of microstructure over the grain size range of 10-80 nm. This indicates that the underlying physical processes of grain boundary-mediated damage formation are strain-oriented phenomena that can be defined by a critical plastic strain regardless of the strength of the material as a whole.