Influence of free surface orientation on plasticity nucleation in BCC metals

Abstract

The peculiarities of plasticity nucleation in iron nanowires under uniaxial tension along different crystallographic directions were investigated. The study was carried out on the basis of molecular dynamics calculations. It was shown that the nucleation of plasticity in samples is associated with the nucleation of either twins or dislocations. The tension of a single crystal sample along the [112̅] direction leads to the nucleation and growth of a twin. In this case, dislocations generate and propagate only in the body of the formed twin. The tension of the sample along the [1 1̅ 0] direction resulted in the nucleation of numerous twins at the front of which regions with fcc and hcp lattices arise. During tension along the [111] direction, the plasticity nucleation is associated with an avalanche-like generation of screw dislocations. Formed dislocations escape on free surfaces and leave a large number of vacancies in the sample.