Formation of Structure and Phase Composition in Ecviatomic Alloys of Cu–Ni–Al–Fе–Cr System Synthesized by Mechanical Alloying

Abstract

Nanocrystalline equiatomic high-entropy alloys (HEAs) have been synthesized by mechanical alloying in Cu–Ni–Al–Fе–Cr system from the binary CuNi alloy to the quinary CuNiAlFeCr alloy. By using X-ray diffraction analysis structure and phase evolution during mechanical alloying (MA) in binary to quinary alloys selected from Cu, Ni, Al, Fe и Cr in sequence were investigated. Binary CuNi alloy formed solid solution with face-centered cubic crystal structure in nanocrystalline state. Ternary to quinary alloys (CuNiAl, CuNiAlFe CuNiAlFeCr) first formed solid solution with body-centered cubic crystal structure in nanocrystalline state and then transformed into XRD-amorphous phase at the end of MA. No precipitation of the second phase such as intermetallic phase was found. The alloying sequence for the present alloy system during MA is determined as Cu→Ni→Al→Fe→Cr in the order of decreasing alloying rate. The alloying rate is found to correlate with the melting temperature of the elements. This correlation is explained through the effect of melting temperature on solid diffusion.