Simultaneously enhancing the tensile strength and ductility of high entropy alloys by nanoscale precipitates/fillers

High entropy alloys (HEAs) in the solid solution (SS) phase have attracted much attention due to their novel strengthening mechanisms. Recent studies have shown that introducing nanoscale precipitates/fillers can further strengthen the SS HEAs. In this work, we performed large-scale molecular dynamics simulations of AlxCoCuFeNi HEAs filled with randomly distributed AlNi3 nanoparticles. The effects of AlNi3 particle size and volume fraction, the chemical composition of the HEA matrix, and temperature on the mechanical properties, deformation, and failure behavior of the composite are systematically investigated. Our simulations show that, remarkably, the AlNi3 nanoparticles can simultaneously enhance the ultimate tensile strength and ultimate tensile strain of the composite. The underlying mechanism is that the AlNi3 nanoparticles greatly suppressed the phase change and dislocation appearance in the HEA matrix, resulting in a delayed material failure during the deformation. We also find that Young’s modulus, ultimate tensile strength, and ultimate tensile strain follow the lower-bound of the rule of mixtures and further present the underlying reason for this lower-bound relation. The present work not only provides insights into the mechanical properties, deformation, and failure behavior of AlNi3 nanoparticle-reinforced AlxCoCuFeNi HEAs but is also useful for guiding the rational design of HEAs for engineering applications.