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 system