Abstract:
A CoCrCuFeNi high entropy alloy (HEA) prepared by mechanical alloying (MA) exhibits evolution of two
phases, a BCC phase (a = 0.287 ± 0.002 nm) and a small amount of FCC phase (a = 0.362 ± 0.002 nm)
after 65 h of milling. From the scanning electron micrographs, flaky nature of milled powders and a wide
range of particle size (5 to 10 μm) can be seen. The nanostructure of the crystallites evolved in the 65 h
milled powder was analyzed using XRD and selected area electron diffraction techniques. The stability of
the 65 h milled powder is studied through in situ high-temperature X-ray diffraction (HT-XRD) over a
range of temperatures. The as-milled powder is thermally stable up to 623 K, and then the precipitation of
the tetragonal(Cr-Co/Fe) based sigma (σ) phase (a = 0.845 ± 0.002 nm, c = 0.454 ± 0.002 nm) occurs.
On annealing at 623 K, precipitation of theσ phase started, while on annealing at 1073 K the BCC phase
disappears associated with a decrease in the amount ofσ phase. Eventually, the FCC phase
(a = 0.362 ± 0.002 nm) appeared to be the stable phase along with a negligible amount of σ phase.
