Atomic simulation for the effect of short-range order and twin boundary on mechanical behavior of FeNiCrCoAl high-entropy alloys

Short-range order (SRO) structure has been considered a potential strengthening method to improve the mechanical properties of high-entropy alloys (HEAs). However, the reinforcement mechanism of SRO structure on the HEA is still unclear. Here, the effect of SRO degree, twin boundary (TB) and temperature on the mechanical properties of the FeNiCrCoAl HEAs with different Al contents under uniaxial tensile is investigated using molecular dynamics/Monte Carlo simulations. The results indicate that the strengthening effect caused by the SRO structure and the softening effect caused by the addition of Al atoms coexist in the HEAs, and their competition determines the mechanical properties of the HEAs. And the softening caused by Al atoms dominates the mechanical properties of the HEAs, and the mechanical properties of the HEAs decrease with the increase of Al content. The results show that Al content has a significant impact on the SRO structure of the HEAs and the degree of SRO decreases in the HEAs with the increase of Al content. It is worth noting that under the same alloy composition, the strengthening effect of the SRO structure on the alloys first increases and then decreases with increasing the degree of SRO. The results indicate that the strengthening effect of the SRO structure and TB together is greater than that of TB or SRO alone. In addition, the results also show that higher temperature is not conducive to the stability of SRO structure, and the strengthening effect of SRO on the HEAs decreases with the increase of temperature.