Solid Solution or Intermetallics in a High-Entropy Alloy

NiAl intermetallic phases were identified in AlCrFeCoNiCu alloy, indicating that the mixing entropy is not sufficient to inhibit the Al and Ni atoms from forming intermetallics in this alloy system. The AlCrFeCoNiCu alloy ingots were prepared by a vacuum arc melting the mixtures of pure Al, Cr, Fe, Co, Ni, and Cu with purities of better than 99.9 mass% in a Ti-gettered high-purity argon atmosphere. The ingots were remelted four times to improve homogeneity and then directly solidified in the cold copper hearth. A Hitachi S-5500 scanning electron microscope equipped with EDS was used to identify the element distribution of as-cast AlCrFeCoNiCu alloy in nanoscale. The AlCrFeCoNiCu alloy displays typical ferromagnetic behavior because of the decomposition of paramagnetic NiAl intermetallics and a magnetic solid solution. The ordered bcc phase was also detected in AlSiTiCrFeCoNiMo0.5 and AlSiTiCrFeCoNiMo0.5 alloys.