Decomposition in multi-component AlCoCrCuFeNi high-entropy alloy

The decomposition of an equiatomic AlCoCrCuFeNi high-entropy alloy produced by splat quenching and casting was investigated by the analytical high resolution methods: transmission electron microscopy and three-dimensional atom probe. It could be shown that splat-quenched alloy consisted of an imperfectly ordered body-centred cubic phase with a domain-like structure, whereas normally cast alloy formed several phases of cubic crystal structure. The cast alloy decomposed into both dendrites and interdendrites. A detailed local compositional analysis carried out by atom probe within the dendrites revealed that the alloying elements in the Ni-Al-rich plates and Cr-Fe-rich interplates are not randomly distributed, but segregate and form areas with pronounced compositional fluctuations. Cu-rich precipitates of different morphologies (plate-like, spherical and rhombohedron-shaped) could also be found in the dendrites. The results are discussed in terms of segregation processes governed by the enthalpies of mixing of the binary systems.