Molecular dynamics simulation of primary radiation damage in W-Ta alloys: Effect of tantalum

Abstract

Tungsten (W) and W-based alloys are competitive candidates for plasma-facing materials in future fusion reactors. W-tantalum (Ta) alloys get the most attention amongst these materials. The present study uses molecular dynamics simulations to study the displacement cascades of pure W and W-Ta alloy systems with recoil energy up to 100 keV at 300 K and the further evolution of cascade defects at 1,000 K. The effects of Ta concentration on the generation and evolution of the defects, produced with primary knock-on atom energies, are quantitatively analysed. This study's results show that the presence of randomly distributed Ta atoms does not significantly affect the average number of surviving Frenkel pairs or the fractions of clustered vacancies and interstitials. In addition, there is no completed vacancy dislocation loop in all systems after cascading. The produced dislocation loops are mainly 1/2 〈111〉 loops companied with a small amount of 〈100〉 loops and mixed loops. However, the existence of Ta atoms slows down the motion of defects and defect mobility decreases as the Ta concentration increases in bulk W. This will affect the size and density of defects. In addition, the presence of Ta also inhibits the transition of the 〈100〉 dislocation loops to 1/2 〈111〉 dislocation loops under the high-temperature condition. This will affect the types of dislocation loops and the material performance.