The Hall–Petch breakdown in nanocrystalline metals: A crossover to glass-like deformation

The deformation behavior of nanocrystalline Ni–W alloys is evaluated by nanoindentation techniques for grain sizes of 3–150 nm, spanning both the range of classical Hall–Petch behavior as well as the regime where deviations from the Hall–Petch trend are observed. The breakdown in strength scaling, observed at a grain size of 10–20 nm, is accompanied by a marked transition to inhomogeneous, glass-like flow (i.e. shear banding) at the finest grain...