Chemical short-range order increases the phonon heat conductivity in a refractory high-entropy alloy

Abstract

We study the effects of the chemical short-range order (SRO) on the thermal conductivity of therefractory high-entropy alloy HfNbTaTiZr using atomistic simulation. Samples with different degreesof chemical SRO are prepared by a Monte Carlo scheme. With increasing SRO, a tendency of formingHfTi and TiZr clusters is found. The phonon density of states is determined from the velocity autocorrelation function and chemical SRO modifies the high-frequency part of the phonon density ofstates. Lattice heat conductivity is calculated by non-equilibrium molecular dynamics simulations.The heat conductivity of the random alloy is lower than that of the segregated binary alloys. Phononscattering by SRO precipitates might be expected to reduce scattering times and, therefore, decreasethermal conductivity. We find that, in contrast, due to the increase of the conductivity alongside SROcluster percolation pathways, SRO increases the lattice heat conductivity by around 12 %. This isexpected to be a general result, extending to other HEAs.