New mechanisms of dislocation line-loop interactions in BCC-Fe explored by molecular dynamics method

Abstract

Development and safe application of nuclear energy depend on the performance of the structural materials. Mechanical property degradation of irradiated metals has been confirmed to be closely related with the interactions between dislocations and radiation defects. To understand the underlying interaction mechanism at atomic scale is significant for development of radiation resistant materials in future. In this work, three different kinetic mechanisms have been suggested by simulating the interactions between a 1/2[111] screw dislocation line and 1/2 〈111〉 interstitial dislocation loops with different orientations in the body-centered cubic (BCC) iron system. Molecular dynamics (MD) simulations indicate that formation of a helical turn configuration, cross-slip movement, and diffusion of screw segments on loop core during pinning and unpinning process are primary features related to three new interaction mechanisms. Detailed analysis suggests that for a given screw dislocation line, the specific Burgers vector of a 1/2 〈111〉 interstitial dislocation loop and its size determine the dominated mechanism for a line-loop interaction. It is also found that the critical stress for a screw dislocation to cross a 1/2 〈111〉 dislocation loop is varied due to the interactions involved in these new mechanisms. All these results provide new insights into the evolution of microstructure in irradiated BCC iron.

Keywords

• Pinning mechanism
• Helical turn
• Screw dislocation
• Dislocation loop
• Molecular dynamics