Molecular dynamics simulation of the interaction between a mixed dislocation and a stacking fault tetrahedron

Abstract

A high number-density of nanometer-sized stacking fault tetrahedra are commonly found during irradiation of low stacking fault energy metals. The stacking fault tetrahedra act as obstacles to dislocation motion leading to increased yield strength and decreased ductility. Thus, an improved understanding of the interaction between gliding dislocations and stacking fault tetrahedra are critical to reliably predict the mechanical properties of irradiated materials. Many studies have investigated the interaction of a screw or edge dislocation with a stacking fault tetrahedron (SFT). However, atomistic studies of a mixed dislocation interaction with an SFT are not available, even though mixed dislocations are the most common. In this paper, molecular dynamics simulation results of the interaction between a mixed dislocation and an SFT in face-centered cubic copper are presented. The interaction results in shearing, partial absorption, destabilization or simple bypass of the SFT, depending on the interaction geometry. However, the SFT was not completely annihilated, absorbed or collapsed during a single interaction with a mixed dislocation. These observations, combined with simulation results of edge or screw dislocations, suggest that defect-free channel formation in irradiated copper is not likely by a single dislocation sweeping or destruction process, but rather by a complex mix of multiple shearing, partial absorption and defect cluster transportation that ultimately reduces the size of stacking fault tetrahedra within a localized region.

Keywords:

• stacking fault tetrahedron
• clear channel formation
• mixed dislocation
• dislocation interactions
• irradiation effects
• mechanical properties
• microstructure change
• molecular dynamic simulations

Acknowledgements

The authors gratefully acknowledge the financial support of the National Science Foundation under contract NSF DMR 0244562 and the Department of Energy, Office of Fusion Energy Sciences under grant DE-FG02-04GR54750. We are grateful to Ian Robertson and Richard LeSar for their careful reading of the manuscript and suggestions for our presentation.

Notes

Note

1. Throughout this paper, the abbreviation SFT will be used to refer to an isolated stacking fault tetrahedron, and stacking fault tetrahedra will be used to refer to a distribution of stacking fault tetrahedra.