Effects of rare earth elements on AlCoCrFeNi2.1 eutectic high-entropy alloy

In order to explore the effect of rare earth elements (REEs) on the eutectic high-entropy alloys (EHEAs), 0.2 atomic per cent of Sc, Y, and La elements were added to the AlCoCrFeNi 2.1 (REE0) EHEA in this work. The phase composition, element distribution, electrochemical properties and mechanical properties of the alloys were analysed. The results showed that the AlCoCrFeNi 2.1 -based HEAs are still composed of Co, Cr, Fe (face-centred cubic)-rich phase and Al, Ni (face-centred cubic)-rich phase. After Sc, Y, La were added, Ni 2 Sc, Al 2 Y, Al 2 La and other intermetallics were formed in the AlCoCrFeNi 2.1 alloy. In addition, it was proved that Y element can promote the formation of hexagonal close-packed (HCP) phase. AlCoCrFeNi 2.1 Y 0.2 (Y0.2) alloy has excellent corrosion resistance. AlCoCrFeNi 2.1 Sc 0.2 (Sc0.2) alloy has the best mechanical properties. HIGHLIGHTS With the addition of rare earth elements, the face-centred cubic phase and the B2 phase still exist in the alloy. In addition, there are intermetallics in the alloys. Combined with first-principles calculations, it was determined that the Laves phases in AlCoCrFeNi 2.1 Y 0.2 alloy may be Al 2 Y, Al 3 Y or AlY. The Laves phase in the AlCoCrFeNi 2.1 La 0.2 alloy may be Al 2 La, Al 3 La or LaNi 5 . The addition of Y element can promote the formation of HCP phase in AlCoCrFeNi 2.1 alloy. The generated HCP phase occupies the position of the original B2 phase. Y element can also improve corrosion resistance. The Vickers hardness of AlCoCrFeNi 2.1 Sc 0.2 alloy is 20% higher than that of AlCoCrFeNi 2.1 alloy, while the compressive strength of 1897 MPa and the compressive deformation of 26% are retained.