Investigation of phases in Al23Co15Cr23Cu8Fe15Ni16 and Al8Co17Cr17Cu8Fe17Ni33 high entropy alloys and comparison with equilibrium phases predicted by Thermo-Calc

Al23Co15Cr23Cu8Fe15Ni16 and Al8Co17Cr17Cu8Fe17Ni33 high entropy alloys were investigated by scanning electron microscopy, transmission electron microscopy and three dimensional atom probe. While the brittle Al23Co15Cr23Cu8Fe15Ni16 alloy decomposes during solidification mainly into two body centred cubic phases, the ductile Al8Co17Cr17Cu8Fe17Ni33 shows two prominent face-centred cubic phases. Al23Co15Cr23Cu8Fe15Ni16 consists of Fe–Cr-rich and Cu-rich intermetallic phases embedded in an Al–Ni-rich solid solution matrix. The microstructure of Al8Co17Cr17Cu8Fe17Ni33 is mainly characterized by two phases. Nano-sized precipitates enriched mainly in Ni are embedded in a matrix depleted in Al and Cu. The phases observed in both high entropy alloys are compared with the equilibrium phases predicted by Thermo-Calc simulation.

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