Atomic Mechanisms Governing Strength of Metallic Nanosized Crystals

Abstract

Fundamentals of the atomic mechanisms governing the strength of nanosized metallic crystals are described. An attempt is made to explain on this basis the size and orientation effects, temperature dependence of strength and atomism of fracture of bcc crystals under triaxial uniform (hydrostatic) tension. A feature of the proposed material is that it com-bines the results of molecular dynamics simulation with the data of experimental research findings on failure of metallic nanosized crystals under the high-field mechanical loading. It is exhibited that local instability of the lattice is the main mechanism governing the strength of defect-free nanosized crystals (NSC). Based on the concept of local instability, an explanation is given of the nature of the size effect in NSC, as well as of the differences in its manifestation in nanocrystals with bcc and fcc lattices. The concept of the mechanism of thermal activation of local instability is outlined. This enables to explain the specific features of the temperature dependence of NSC. The results of experimental studies and molecular dynamics simulation of the failure of tungsten nanocrystals under hydrostatic tension are presented. The ideas about the atomism of the bcc-fcc transition in these conditions are articulated. as a result of electrochemical polishing. This means that formation of an atomically smooth surface of nanoneedles is one of the factors to reach the ultimate strength levels.