Atomistic study of temperature dependence of interaction between screw dislocation and nanosized bcc Cu precipitate in bcc Fe

Molecular dynamics simulations of the interaction between a screw dislocation and a 3.5 nm diameter bcc Cu precipitate in bcc Fe have been performed in the twinning and antitwinning direction between 10 and 400 K. The results indicate a significant temperature dependence in the antitwinning direction, whereby the screw dislocation bypasses the Cu precipitate by Orowan looping below 200 K, but shears the precipitate above 300 K. The transition in interaction mechanism is caused by a screw dislocation assisted martensitic transformation of the Cu precipitate, which significantly diminishes above 300 K. The screw dislocation shears the precipitate at all temperatures between 10 and 400 K in the twinning direction. Thus, transformation of the precipitate induces additional precipitate strengthening below 200 K in the antitwinning direction, which drastically decreases with increasing temperature above 300 K. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3003083]