Investigation of phases in Al_(23)Co_(15)Cr_(23)Cu_8Fe_(15)Ni_(16) and high entropy alloys and comparison with equilibrium phases predicted by Thermo-Calc

摘要

Al_(23)Co_(15)Cr_(23)Cu_8Fe_(15)Ni_(16) and Al_8Co_(17)Cr_(17)Cu_8Fe_(17)Ni_(33) high entropy alloys were investigated by scanning electron microscopy, transmission electron microscopy and three dimensional atom probe. While the brittle Al_(23)Co_(15)Cr_(23)Cu_8Fe_(15)Ni_(16) alloy decomposes during solidification mainly into two body centred cubic phases, the ductile Al_8Co_(17)Cr_(17)Cu_8Fe_(17)Ni_(33) shows two prominent face-centred cubic phases. Al_(23) Co_(15)Cr_(23)Cu_8Fe_(15)Ni_(16) consists of Fe-Cr-rich and Cu-rich intermetallic phases embedded in an Al-Ni-rich solid solution matrix. The microstructure of Al_8Co_(17)Cr_(17)Cu_8Fe_(17)Ni_(33) 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.