Atomistic investigation of Cr influence on primary radiation damage in Fe-12 at.% Cr grain boundaries

Abstract

In this paper, we investigate the influence of Cr on the primary radiation damage in Fe-12 at.% Cr with different atomic grain boundaries (GBs). Four different GB structures, two twists and two symmetric tilt boundaries are selected as the model structures. The primary radiation damage near each GB in α-Fe and Fe-12 at.% Cr is simulated using Molecular Dynamics for 9 keV primary knock-on atoms with velocity vectors perpendicular to the GB plane. In agreement with previous works, the results indicate that the atomic GBs are biased toward interstitials and due to the reduction of ‘in-cascade’ interstitial-vacancy annihilation rates, vacancies accumulate in the bulk grains. The minimum defect production occurs when the overlap between cascade center and GB plane is maximum; in contrast, the number of residual defects in the bulk (vacancies and interstitials) increases when the overlap decreases. Moreover, we find that the presence of Cr hardly affects the number of residual defects in the grain interiors, and causes a Cr-enrichment in the surviving self-interstitial atoms in bulk during relaxation of the primary cascades—also in agreement with previous studies. Further, in order to study the effect of 12 at.% Cr on the energetic and kinetic properties of vacancies near the atomic GBs, we calculate formation energies and diffusion barriers of defects using Molecular Static and climbing-Nudged Elastic Band methods. The results reveal that the vacancies energetically and kinetically tend to form and cluster around the GB plane due to the substantial reduction of their formation energies and migration barriers in layers close to the GB center and are immobile on the simulated time frame (~ps).

Primary radiation damage of Zr-0.5%Nb binary alloy: atomistic simulation by molecular dynamics method

“…This phenomenon is important for a better understanding of niobium atom migration under irradiation. The same phenomena have been considered in [6][7][8][9][10][11][12] for the Fe-(5%-15)% Cr alloys. There, atomistic simulation has shown that a relatively small positive binding energy between the Cr atoms and SIA configurations in the bcc Fe (∼0.1 eV for the energetically most preferred configuration) leads to an increased concentration of chromium in the SIAs produced in atomic displacement cascades.…”

“…The target values of 2.76 and 0.61 eV for the self-interstitial formation energy and substitution energy, respectively, were taken from ab initio calculations performed by Domain [4]. The obtained values of the fitted parameters are A = 358.0 eV • Å 6 and B = 118 140.0 eV • Å 12 .…”