Influence of Al atomic distribution on mechanical properties of high-entropy alloys with gradient ingrain size

Abstract

High-entropy alloys (HEAs) have been extensively studied across various fields as a novel class of multi-major element alloys. To meet the increasing demand for higher strength materials, the properties of HEAs can be optimized through structural and compositional design. In this study, a gradient structure in grain size was introduced into HEAs, and the impact of different Al atomic distribution patterns on the mechanical properties of HEAs under uniaxial tensile loading was investigated using molecular dynamics simulations. The results indicate that a non-uniform Al atomic distribution effectively enhances the material’s strength, particularly in the dual-gradient model, where the Al atomic concentration decreases with increasing grain size. This model has the best strength but essentially no effect on ductility. Significant geometrically necessary dislocations were observed at the boundaries of the soft and hard regions, contributing to hetero-deformation induced hardening. Additionally, regions with low Al atomic concentration are more likely to form sessile dislocation structures, which provide strengthening effects. When the two gradient structures are sensibly combined, they can result in a positive joint contribution to the material’s strength. This work provides effective guidance for improving the mechanical properties of HEAs.