High Temperature Tensile and Compressive Behaviors of Nanostructured Polycrystalline AlCoCrFeNi High Entropy Alloy: A Molecular Dynamics Study

Molecular dynamics studies were performed to assess tensile and compressive behaviors at high temperatures up to 1200 degrees C for nanostructured polycrystalline AlCoCrFeNi high entropy alloy (HEA). As the temperature increased, the tensile yield stress, tensile/compressive ultimate strengths, and elastic modulus decreased, whereas the compressive yield stress remained constant. The temperature dependence of the phase structures (face-centered cubic (FCC) and hexagonal close-packed (HCP)) showed notable features between tension and compression. The HEA underwent FCC -> HCP phase transformation when strained under both tension and compression. The evolution of the intrinsic stacking faults (ISFs) and extrinsic stacking faults (ESFs), which underwent FCC -> HCP phase transformation, was observed. During compression, the ISFs -> ESFs transition produced parallel twins. The evolution of mean dislocation length for the perfect, Shockley, and stair-rod partial dislocations was observed. Changes in the Shockley and stair-rod partial dislocations were observed after experiencing strain. The temperature dependence of the Shockley partial dislocation was high, whereas the stair-rod partial dislocation exhibited low-temperature dependence. From the simulation results, the structural usage of nanostructured polycrystalline AlCoCrFeNi HEA at elevated temperatures is recommended.

Automated summary

Molecular dynamics simulations were used to study the tensile and compressive behaviors of nanostructured polycrystalline AlCoCrFeNi high entropy alloy at high temperatures. The results showed that the tensile yield stress, tensile/compressive ultimate strengths, and elastic modulus decreased with increasing temperature, while the compressive yield stress remained constant. The FCC->HCP phase transformation was observed under both tensile and compressive strains, and the evolution of intrinsic and extrinsic stacking faults was also studied. The mean dislocation length and the changes in Shockley and stair-rod partial dislocations were analyzed, and the temperature dependence of these dislocations was investigated. Based on the simulation results, the structural application of the alloy at elevated temperatures was recommended.