Effect of structural modulation of B2 phase on the deformation mechanism in FeNiCrCoAl high entropy alloy: an atomistic insight

Abstract

Tuning the microstructure is critically significant for enhancing the mechanical properties of dual-phase FeNiCrCoAl high-entropy alloys (HEAs), often achieved through compositional variation. However, the influence of microstructural characteristics on fundamental deformation mechanisms remains scarcely explored. In this study, molecular dynamics (MD) simulations combined with density functional theory (DFT) were employed to design FeNiCrCoAl HEAs with varying Al content and number of B2 grains to elucidate their tensile deformation behaviour across various temperatures. The findings indicate that specimens with fewer B2 grains exhibit superior plasticity, whereas an increased fraction of B2 grains contributes to higher strength. The BCC phase was observed to impede dislocation mobility within the FCC matrix while facilitating dislocation interactions, leading to the formation of Lomer–Cottrell locks. At elevated temperatures, the deformation mechanism transitioned from dislocation-mediated processes to interfacial diffusion, as evidenced by atomic strain and displacement analyses. Notably, the FCC–BCC interface was found to play a pivotal role in enhancing interfacial atomic mobility, thereby intensifying plastic deformation under high-temperature conditions.