An assessment of the elemental segregation in equimolar AlCuFeMn medium-entropy alloy using cluster expansion and Monte Carlo simulation

Abstract

Although the high-entropy effect in (near-)equimolar, multicomponent alloy systems supposedly randomize elemental distribution, experimental observations demonstrate the presence of atomic ordering and elemental segregation in several systems. Equimolar AlCuFeMn alloy is one such system, demonstrating Cu-rich and Fe–Mn-rich phases in cast and annealed samples. To gather fundamental insight into such microstructural evolution, in this study, we computationally examined the intricate chemical nature of the AlCuFeMn alloy, leading to elemental segregation. We employed density functional theory-based cluster expansion and Monte Carlo (MC) simulations on the experimentally reported phases of AlCuFeMn at room temperature, viz., B2, L21, and L12. The current study confirms short-range ordering vis-à-vis elemental segregation in these phases. We attribute these effects to the chemical affinity of the constituent elements. The present study emphasizes the critical role of binary mixing enthalpy in determining short-range order. Additionally, MC simulations demonstrate that atomic distributions are temperature-dependent, indicating that, above approximately 1750 K, an order–disorder transition takes place.