It was recalled that grain-boundary engineering was a prospective tool for producing high-performance structural and functional materials, including super-strong nanocrystalline materials. There remained a fundamental challenge to experimentally evaluating the inherent strength of grain boundaries providing a higher limit for the strength of polycrystals. It was reported here, using a combination of atomic-scale and crystallographic characterizations and in situ hydrostatic tests in a field-ion microscope, that the inherent strength of grain boundaries could be directly measured. It was found that mechanically annealed dislocation-free tungsten bicrystals having nanometer-sized dimensions were capable of withstanding extreme stresses close to the values of the theoretical strength of monocrystals. This finding provides a guideline for understanding the fundamental mechanical response of nanocrystals relevant to applications.

Inherent Strength of Grain Boundaries in Tungsten. I.M.Mikhailovskij, T.I.Mazilova, V.N.Voyevodin, A.A.Mazilov: Physical Review B, 2011, 83[13], 134115