Effect of aluminum on fine structure and distribution of chemical elements in high-entropy alloys Al x FeNiCoCuCr

Electron-microscopic and X-ray diffraction methods have been used to study the fine structure of cast high-entropy alloys (HEAs) Al (x) FeNiCoCuCr (x = 1, 1.5, 1.8). Disperse precipitates with dimensions of 130-400 and 10-20 nm have been revealed, the character of distribution of which, as well as the amounts, dimensions, and shapes, change with increasing aluminum content. In the equiatomic HEA, copper-containing particles with an fcc structure have been found; in the alloy with x = 1.8, particles of bcc Al4Cu9 dominate. It has been shown that the most uniform distribution over the matrix is characteristic of Co, unlike other elements, among which Cu and Cr are distributed in the alloy extremely nonuniformly and predominantly enter into the precipitated particles and into clusters in the interparticle spaces, respectively.