Abstract
Multi-element high-entropy alloys (HE alloys) are new alloys with over five principal elements each having an atomic percentage no more than 35%. Using the alloys, e.g. Al 0.5 CoCrCuFeNi, Al 2 CoCrCuFeNi, and AlCrNiSiTi, as target materials in reactive sputtering, nanostructured metallic and nitride films were deposited. XRD patterns show that the alloy films of Al x CoCrCuFeNi are crystalline with structures of simple fcc or mixed bcc+fcc solid solution, and the crystallinity decreases and approaches an amorphous structure with increasing nitrogen flow rate into the processing chamber. Unlike the Al x CoCrCuFeNi HE alloys, the metallic film of AlCrNiSiTi is amorphous and its hardness is much higher than the hardest nitride films of Al x CoCrCuFeNi alloy. TEM, FESEM and AFM observations show that the films morphology and structure evolution with N 2 /Ar fraction is different between Al x CoCrCuFeNi and AlCrNiSiTi HE alloys. The slope of films resistivity versus N 2 /Ar ratio is much steeper in AlCrNiSiTi than in Al x CoCrCuFeNi HE alloy. The hardness enhancement in nitrides is less significant in AlCrNiSiTi than in Al x CoCrCuFeNi HE alloys. © 2005 Elsevier B.V. All rights reserved.