Molecular dynamics simulations of hcp/fcc nucleation and growth in bcc iron driven byuniaxial compression

Abstract

Molecular dynamics simulations have been performed to study thestructural transition in bcc iron under uniaxial strain loading. We foundthat the transition pressures are less dependent on the crystal orientations,∼14 GPa for [001], [011], and [111] loadings. However, the pressure interval of a mixedphase for [011] loading is much shorter than loading along other orientations. Inaddition, the temperature increased amplitude for [001] loading is evidently lowerthan other orientations. The nucleation and growth of the hcp/fcc phases, andtheir crystal orientation dependence, were analyzed in detail, where the atomstructure was presented by the topological medium-range-order analysis. For [001]compression, the hcp structure occurs first and grows into a laminar morphology in the(011)bcc plane with some fcc atoms as an intermediate structure. For loading along [011]and [111] directions, both hcp and fcc structure nucleation and growth along the{110}bcc planes are observed; their morphology is also discussed.