Thermal Stability and Strengthening Effect of Coherent Precipitates in a (FeCoNi)92Al2.5Ti5.5 High Entropy Alloy

Abstract

The coarsening behavior and strengthening effect of L1₂-Ni₃(Ti,Al) precipitates in a face-centered-cubic (FCC) (FeCoNi)₉₂Al_2.5Ti_5.5 high entropy alloy have been systematically investigated. The coherent L1₂ precipitates, uniformly distributed throughout the FCC matrix, consistently retain a spherical shape. The coarsening rate coefficient of precipitate is determined by employing the Philippe-Voorhees (PV) model, suggesting excellent thermal stability. Furthermore, the elemental partitioning and compositional evolution of the L1₂ precipitates is analyzed by atom probe tomography, which identify aluminum (Al) as the slowest diffusion species during the coarsening process. In addition, the precipitation strengthening effect is quantified to ascertain the optimal size of the precipitates. Our study enhances the understanding of precipitate coarsening in high entropy alloys, presenting valuable insights into their thermal stability and mechanical properties.