Re-W

Abstract: Tungsten (W) and W-based alloys are the leading candidates for plasma-facing materials (PFMs) in future fusion reactors. However, the high energy neutrons generated in fusion reactions not only result in cascade damages but also cause W transmutation. Both the irradiation defects and transmutation products, mainly rhenium (Re), have serious effects on the service behaviors of W PFMs. In this work, we have systematically investigated the interaction between Re and the self-interstitial atoms, self-interstitial clusters and 1/2<111> interstitial dislocation loops in bulk W using molecular dynamics and statics simulations. It is found that there is a strong attractive interaction between an interstitial W atom and a substitutional Re atom, forming a Re–W dumbbell that migrates 3-dimentionally due to the low migration and rotation energies. The small SIA clusters strongly bind with both the substitutional Re atoms and an interstitial Re atom (Re–W mixed dumbbell), thus decreasing the mobility of these clusters. The strong attractive interaction between a Re atom and a 1/2<111> interstitial dislocation loop occurs when the Re atom is located at the core of the loop, and also, their interaction distance along <111> direction is large. The mobility of the 1/2<111> interstitial dislocation loop decreases progressively with increasing Re concentration.

Abstract: Tungsten (W) and W-based alloys have been considered as promising candidates for plasma-facing materials (PFMs) in future fusion reactors. The formation of rhenium (Re)-rich clusters and intermetallic phases due to high energy neutron irradiation and transmutations significantly induces the hardening and embrittlement of W. In order to better understand these phenomena, in the present work, new interatomic potentials of W-W, Re-Re and W-Re, suitable for description of radiation defects in such alloys, have been developed. The fitted potentials not only reproduce the results of the formation energy, binding energy and migration energy of various radiation defects and the physical properties from the extended database obtained from DFT calculations, but also predict well the relative stability of different interstitial dislocation loops in W, as reported in experiments. These potentials are applicable for describing the evolution of defects in W and W-Re alloys, thus providing a possibility for the detailed understanding of the precipitation mechanism of Re in W under irradiation.

Abstract: A tungsten-rhenium (W-Re) classical interatomic potential is developed within the embedded atom method interaction framework. A force-matching method is employed to fit the potential to ab initio forces, energies, and stresses. Simulated annealing is combined with the conjugate gradient technique to search for an optimum potential from over 1000 initial trial sets. The potential is designed for studying point defects in W-Re systems. It gives good predictions of the formation energies of Re defects in W and the binding energies of W self-interstitial clusters with Re. The potential is further evaluated for describing the formation energy of structures in the σ and χ intermetallic phases. The predicted convex-hulls of formation energy are in excellent agreement with ab initio data. In pure Re, the potential can reproduce the formation energies of vacancies and self-interstitial defects sufficiently accurately and gives the correct ground state self-interstitial configuration. Furthermore, by including liquid structures in the fit, the potential yields a Re melting temperature (3130 K) that is close to the experimental value (3459 K).

Abstract: In this work, an interatomic potential for the W-Re system is fitted and benchmarked against experimental and density functional theory (DFT) data, of which part are generated in this work. Having in mind studies related to the plasticity of W-Re alloys under irradiation, emphasis is put on fitting point-defect properties, elastic constants, and dislocation properties. The developed potential can reproduce the mechanisms responsible for the experimentally observed softening, i.e., decreasing shear moduli, decreasing Peierls barrier, and asymmetric screw dislocation core structure with increasing Re content in W-Re solid solutions. In addition, the potential predicts elastic constants in reasonable agreement with DFT data for the phases forming non-coherent precipitates (σ- and χ-phases) in W-Re alloys. In addition, the mechanical stability of the different experimentally observed phases is verified in the temperature range of interest (700–1500 K). As a conclusion, the presented potential provides an excellent tool to study plasticity in W-Re alloys at the atomic level.