Microstructural evolution and phase selection during solidification of AlCrCuFeNi high entropy alloy

An equiatomic AlCrCuFeNi high entropy alloy (HEA) was synthesized by arc melting. The as-cast material exhibits the formation of the two-phase structure consisting of BCC and FCC phases. Different heat-treatment schedules were adopted in this investigation for the systematic understanding of the elemental distribution, microstructural evolution and solidification behavior of the alloy. Light microscope and scanning electron microscope (SEM) with EDS analysis was extensively used to characterize the alloy. The results indicate the as-cast material has the primary phase of dendritic structure. The heat-treated sample at 1300 °C, followed by water quenching as well as furnace cooling, primarily showed the Fe-Cr rich BCC phase formation in the dendritic region. The interdendritic space is enriched in Al-Ni rich B2 phase and the Cu rich phase. These outcomes have proximity to the equilibrium phase predictions performed based on the CALPHAD approach. The element Cu plays a crucial role in affecting the solidification behavior of the alloy in the temperature range of 900–1100 °C. This work has shown why understanding the microstructure evolution and solidification behavior is more important in HEAs for their potential future applications.