Strengthening effect of rhenium on different substitution positions of tungsten nanofilm at high temperature : DFT and molecular dynamics simulation

Tungsten-rhenium (W-Re) alloys have excellent high-temperature properties due to the solution strengthening of Re. However, the best strengthening position of Re in W-Re alloy at high temperature is not clear. Therefore, the effects of Re on the high-temperature properties of nano-polycrystalline W-Re film were carried out by using molecular dynamics (MD) simulation and density functional theory (DFT). Our calculated results show that Re atoms at all doping positions can increase the strength and plasticity of the W matrix, the yield strength increased from 18.81 GPa to a maximum of 22.14 GPa, and the yield strain increased from 4.06% to a maximum of 5.46%, because the deformation of the GBAZ increased, resulting in higher plastic hardening and Re changes the directionality of valence electron transfer of W atoms. Among all enhancement sites, the grain boundary affected zone (GBAZ) solid solution (Re atoms distribute in the GBAZ, and there is no Re atom in the grain interior) has the best effect on the yield strength, but based on such model when Re atoms' amount in the grain interior (GI) increased, the yield strength decreased, and the yield strain slightly improved. It is because a contraction force toward the GI is generated when Re dissolves in it, which weakens the strengthening effect of GBAZ solid solution on GBs. In contrast, the GB strengthening energy increases while the bond length at the GBs decreases when more Re atoms dissolve in the GBAZ. Furthermore, the voids in GBs are significantly reduced, and more voids can be held in GBs during the tensile process. The study is helpful to understand the strengthening mechanism of W-Re alloys. © 2019 IOP Publishing Ltd.