Molecular dynamic simulations of displacement cascades in tungsten and tungsten-rhenium alloys: Effects of grain boundary and/or σ phase

Transmutation rhenium (Re) produced in tungsten (W) neutron irradiation not only segregates and pre-cipitates at grain boundaries (GBs) but also forms the sigma-phase (WRe) in the bulk. In this study, using a molecular dynamics (MD) method, we conducted collision cascade simulations in W and W-Re alloys with 5 or 10 at% Re atoms containing a GB/sigma-phase and systematically examined the effect of GB and the evolution of sigma-phase. We find the interstitials in W-Re alloy are preferentially absorbed by the GB region such that the number of vacancies in the bulk region is higher in W-Re alloys than in W; the defect distribution is sensitive to the distance of primary knock-on atoms from the GB plane. Furthermore, similar to the tendency in the GB region, interstitials are preferentially absorbed by the sigma-phase, and Re atoms tend to aggregate near the sigma-phase region. The absorption of sigma-phases and the GB region leads to a considerable defect aggregation, which provides suitable conditions for the regrowth of sigma-phase structure during long-term evolution. The results provide a reference for understanding the GB structure and precipitations in the displacement cascades of W and W-based alloy materials. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Using molecular dynamics simulations, this study investigates the effects of grain boundaries and σ phase evolution in tungsten and tungsten alloys through collision cascade simulations. The results show that in W-Re alloys, interstitials are preferentially absorbed by grain boundaries and σ phases, leading to defect aggregation.