Local-ordering mediated configuration stability and elastic properties of aluminum-containing high entropy alloys

Abstract

Local atomic ordering has been demonstrated to be an effective approach to regulate the mechanical properties of aluminum-containing high-entropy alloys, but the underlying mechanism is not yet well understood. Taking the AlCoCrFeNi2.1 multi-component alloy as a prototype system, the effect of local ordering on its configuration stability and elastic properties were investigated from the aspects of lattice mismatch, modulus mismatch, and chemical bonding, through ab initio calculations. We highlighted that for the bcc phase at 0K, local ordering enhances configuration stability, while it has little influence on the elastic Young's modulus and shear modulus due to severe lattice distortion and elastic distortion in fully disordered configuration. Interestingly, with the increase of temperature, the structural stability and bulk modulus of the partially disordered configuration turns out to be higher than the fully disordered configuration, likely owing to the presence of strong chemical bonding between Al and X(Co, Cr, Fe, Ni). As for the fcc phase in the AlCoCrFeNi2.1 alloy, the degree of local ordering is low and thus results in little difference on the elastic properties between the partially disordered and fully disordered configurations. We believe that our results benefit to the understanding of stabilization mechanism and adjustable mechanical performance of multi-component alloys by considering local ordering.