Molecular dynamics studies of the interaction of a/6 ⟨112⟩ Shockley dislocations with stacking fault tetrahedra in copper. Part I: Intersection of SFT by an isolated Shockley

Abstract

The interactions of Shockley dislocations with stacking fault tetrahedra (SFTs) formed during twinning deformation in fcc crystals have been studied by molecular dynamics using a copper potential. The fundamental mechanisms by which a moving Shockley dislocation interacts with a SFT involve shearing the apex, formation of a residual loop around the SFT and reactions with dislocations at the tetrahedron base. The latter reactions are critical to defect stability; they lead to the formation of Shockley dislocations mobile in two faces of the parent tetrahedron making it penetrable to dislocations moving on adjacent planes during thickening of the twin. Relaxation of SFTs distorted by a homogeneous twinning shear was also studied. These results reveal that parent SFTs convert to structures containing rotated product SFTs, rows of vacancies and stacking faults on planes bounded by partial dislocations. Dislocation mechanisms involved in Shockley–SFT interactions and formation of new defects derived from twin-sheared SFTs are being analyzed.

Keywords:

• molecular dynamic simulations
• Shockley dislocations
• twinning
• stacking fault tetrahedra
• vacancies
• twin-SFT intersections
• twinning dislocations
• irradiation defects
• relaxation mechanisms
• copper

Acknowledgements

This work was supported by the LANL Directed Research and Development Program. One of us, MN, would like to thank the Los Alamos National Laboratory for this financial support during sabbatical leave. We also appreciate the helpful discussions with Prof. John Hirth.