On the problem of the maximum strength of metals and alloys in crystalline,amorphous, and nanocrystalline states

The true breaking stresses and the ultimate tensile strengths of 11 metals with various structures are calculated. Moreover, the fracture strengths of these metals at 0 and 298 K are calculated in the amorphous (σ _{f, a}) and nanocrystalline (σ _f,nano^max) states formed upon severe plastic deformation. The temperature dependences of these properties are also determined. These properties are obtained for a number of alloys (TiNi, NiNb, Pd₈₀Si₂₀, Ni₆₀Nb₄₀). The values of σ _{f, a} are shown to correlate with yield strength σ_{y, nano} of nanocrystalline substances, and a hypothesis of a deviation from the Hall-Petch relation is advanced. This hypothesis is supported by the calculation of the properties and diffusion characteristics. The obtained numerical results agree satisfactorily with the experimental data and the results of other approaches to estimating these properties.