Atomistic simulation of stress-induced phase transformation and recrystallization at the crack tip in bcc iron

The mechanisms of low-temperature deformation at the crack tip in body-centered cubic (bcc) iron have been studied by molecular dynamics simulations. Phase transformation and recrystallization are found to occur at the crack tip when a sufficiently high stress concentration exists. The mechanisms of new grain nucleation and phase transformation in particular are discussed. For {110}< 110 > and {111}< 110 > cracks, phase transformation from the bcc structure to a typical close-packed hexagonal structure is observed accompanying new grain nucleation at the crack tip. It is found to be achieved by the emission of 1/6 < 111 > partial dislocations on the {112} slip plane. 6 For the {100}< 110 > crack, two long twin strips appear at the crack tip along the < 111 > slip direction. A new grain with a different orientation from the original bcc crystal is formed with the growth of the twin region. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.