Impact of local chemical order on the structure evolution of dual-phase high-entropy alloy during solidification process

Abstract

Local chemical order (LCO) may have an important influence on the formation of phase structure in the dual-phase high-entropy alloys (HEAs), so this paper studies the solidification process of AlCoCuFeNi with molecular dynamics simulation. In the melt, there are three obvious chemical orders: Co–Ni, Cu–Fe and Al–Fe. Co, Ni, Cu tend to form FCC phase, Al and Fe tend to form BCC phase. The region with rich Co and Ni is easier to nucleate, so at the initial stage of crystallization, FCC phase is more stable than BCC phase. As the internal energy of Cu is much higher than other elements, which leads to higher Gibbs free energy of FCC phase, during the subsequent crystallization process, BCC phase tends to be more stable. At the end of solidification, the system is composed of BCC phase and FCC phase, BCC phase has more Al, FCC phase has more Cu, and the results are consistent with the experimental results.