Short-range ordering and its impact on thermodynamic property of high-entropy alloys

Abstract

Short-range ordering and atomic segregation have been observed experimentally in high-entropy alloys (HEAs). Understanding their impact on the melting temperature is crucial to the rational design of HEAs. Here we perform molecular dynamics simulations combined with Monte Carlo calculations to study the effects of elemental concentration, short-range ordering and atomic segregation on the melting temperature of AlCoFeNiCux HEAs (x = 0, 0.5 and 1). The simulation results demonstrate that the melting temperature of HEAs increases with decreasing Cu concentration and Cu atoms tend to break bonds more readily than other four types of atoms (Al, Co, Fe and Ni) during heating, even though Cu is not the one with the lowest melting temperature among the constituent component in pure form (melting temperature: Al < Cu < Ni < Co < Fe). We find that the reduced melting temperature is due to the formation of more short-range ordering and atomic segregation with phase boundary when the Cu concentration increases. The formation of short-range ordering and atomic segregation within Cu atoms are consistent with previous experimental observation of Al0.5CoCrFeNiCu HEAs and simulation results of CoCrFeNiCux HEAs (x = 0.4, 0.7 and 1) using another interatomic potential. Our findings highlight the importance of short-range ordering and atomic segregation in influencing the melting temperature of HEAs and provide guide for designing HEAs with desired thermodynamic properties.