Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

Abstract

The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in BCC Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained ≈ 170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15Å of the boundary. The present results provide detailed information about the interaction energies of vacancies and selfinterstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low and high angle grain boundaries were effective sinks for point defects, with a few low-Σ grain boundaries (e.g., the Σ3{112} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and Σ-designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have ≈ 80% more grain boundary sites per area and ≈ 300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7Å vs. 10-11Å for vacancies and interstitials, respectively).

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

“…173,174 Moreover, the atomic structure of the grain boundary has been shown to have an effect on the interaction with point defects. 171,175,176 This fact suggests that increasing the concentration of certain types of boundaries may also be beneficial in radiation resistance of nanocrystalline materials. For instance, molecular dynamics simulations in Cu have shown that the R3 coherent twin boundary, abundant in electrodeposited nanotwinned copper, has a much smaller interaction with radiation defects than most other general boundaries.…”

Atomic-scale analysis of liquid-gallium embrittlement of aluminum grain boundaries

“…125 STGBs were created in Al (<100>, <110> and <111> tilt axes) and equilibrated using MS simulations performed with the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [54].The simulation cell consisted of two single crystal layers meeting at a planar grain boundary with periodic boundary conditions in all three orthogonal directions [45,51,[55][56][57][58][59][60][61]. The thickness of the simulation cell in the direction perpendicular to the boundary plane was ~12 nm (this large value was chosen in order to eliminate any effects associated with the periodic boundary condition).…”

Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

“…As with past work [59][60][61][62][63][64][65][66][67] and others [68][69][70], an atom deletion criterion, multiple initial configurations, and various in-plane rigid body translations were utilized to accurately obtain an optimal minimum energy GB structure via the nonlinear conjugate gradient energy minimization process. Further details on the GB generation technique and GB structures of HCP materials are given in Bhatia and Solanki [59], and Wang and Beyerlein [71].…”