Enhanced energy absorption in high entropy alloys with octet lattice nanostructures

The work focuses on the numerical investigation of compressive mechanical behaviors and energy absorption properties of high entropy alloys (HEAs) with stochastic bicontinuous nanostructures (SBNs) and octet nanostructures (ONs). The study reveals a strong correlation between mechanical behaviors and the relative density of the nanostructures. The findings show that for both ONs and SBNs, the plateau stress increases with increasing the relative density, while an opposite trend is observed for densification strain. The maximum energy absorption capacity is achieved for ONs and SBNs at a relative density 0.6. Additionally, the energy absorption capacity of ONs is higher than that of SBNs across all relative densities, attributed to the higher plateau stress in ONs compared to SBNs. The distinction in mechanical characteristics is further explored by considering the dislocation evolution in ONs and SBNs. The study shows in SBNs that the dislocation increases rapidly, leading to a significant release of stored elastic energy and low plateau stress. Conversely, in ONs, the dislocation increases monotonically, allowing for a gradual release of stored elastic energy and maintenance of high plateau stress. Furthermore, the evolution of atomic configurations demonstrates that intrinsic and extrinsic stacking faults dominate planar defects in ONs, while several types of planar defects play a role in SBNs, including intrinsic stacking fault, extrinsic stacking fault, twin boundary, and hexagonal close-packed laths. The study also shows the effect of temperature on the energy absorption capacity.