Collision Cascade Morphology and Defect Nucleation in Pure Tungsten and an Equimolar Refractory W-Ta-Cr-V Alloy

Abstract

Collision cascades and defect-formation mechanisms in pure W and the WTaCrV refractory high-entropy alloy were investigated using molecular dynamics simulations over primary knock-on atom (PKA) energies of 0.1-100 keV. Machine-learning tabulated Gaussian approximation potentials (tabGAP), complemented by short-range Ziegler-Biersack-Littmark (ZBL) interactions, were employed. Analysis of the heat spike lifetime, affected region, atomic relocations and surviving defects reveals an importance of subcascade formation and presence of light elements in the alloy. Cascade splitting into subcascades contributes to the distribution of the PKA energy over a larger region in the material, nucleating less dislocations and smaller voids - latter being present only in W and absent in WTaCrV. Since cascade splitting is more frequently observed in WTaCrV, the alloy shows better resistance to primary irradiation damage compared to pure W. Apart from cascade splitting, analysis of interstitials shows that Cr and to lesser extent V, being lighter and smaller elements, accommodate the damage in form of point defects, contributing to the mitigation of formation of the dislocation loops.