Effect of Re aggregation doping configurations on the thermal and mechanical properties of W-Re alloys: A molecular dynamics study

Abstract

Thermal and mechanical properties of plasma facing materials (PFMs) are critical for the magnetic confinement fusion devices. In this study, by using molecular dynamics (MD) simulations, we investigate the impact of different dopant configurations and doping levels on the thermal and mechanical properties of W-Re alloys. In the studied models, Re atoms are either randomly distributed in the system, or aggregated with certain shapes (sphere, cone, cylinder, prism, and plane). Accounting for the thermal conductivity and mechanical properties (including the Elastic modulus, Poisson's ratio, and Cauchy pressures, etc.) for the models with different Re aggregation configurations and concentrations, we find that W-Re alloys with spherical Re aggregation configuration exhibit larger thermal conductivity compared with other aggregation configurations regardless of the Re concentration, which also bear good mechanical properties. Also, the thermal conductivity of the spherically doped W-Re alloys as a function of temperature were investigated. The obtained results indicate that as the temperature increases, the phonon scattering increases and the thermal conductivity of the system in general decreases. Furthermore, the normalized phonon density of states (DOS) was calculated to better understand the effect of different doping configurations and concentrations on the thermal conductivity of W-Re alloys. The results show that the model with spherical Re configuration bears a wider phonon frequency domain, indicating inelastic scattering at the W-Re interface. However, when more Re atoms aggregate, the small structural size differences between W and Re atoms are magnified. In this case, the W-Re alloy lattice showed non-negligible distortions, and the whole system exhibited anomalous lattice constants and mechanical properties. Our investigation yields new insights into the physical mechanisms governing heat transport in alloys, and provides guidance to the design of plasma facing materials in terms of thermal transport.