The energy-driven stage-wise phase evolution and nanocrystalline refinement in Cantor (CrCoFeMnNi) high-entropy alloy during mechanical alloying

The development of nanocrystalline high-entropy alloys (HEAs) through mechanical alloying requires a clear understanding of how milling energy influences phase evolution and microstructural refinement. However, the correlation between cumulative impact energy and the formation of a stable nanocrystalline structure in the equiatomic CoCrFeMnNi (Cantor) alloy under mechanical alloying has not been adequately investigated. Thus, the present work explores the influence of energy imparted under BPR=10:1 on phase evolution and microstructural refinement of the Cantor alloy during mechanical alloying. The present research demonstrates a direct correlation between cumulative impact energy, phase transformation, and crystallite refinement across various stages of mechanical alloying. The results showed a stepwise structural transformation from a multiphase structure at 7 h to an FCC-dominant nanocrystalline structure at 20 h. This was accompanied by a significant decrease in the apparent crystallite size of the FCC phase with increasing milling time, from 47.85 nm at 7 h to 19.19 nm at 14 h and to 7.23 nm at 20 h, which confirmed substantial refinement. The Williamson-Hall analysis at 7 h showed a lattice microstrain of the order of 2.8 × 10 −3 , which was almost comparable to 2.75 × 10 −3 at 14 h, indicating increased lattice distortion in the intermediate stages of milling. The progressive broadening of diffraction peaks, which finally resulted in FCC reflections dominating the spectrum, provided further evidence for the increasing atomic interdiffusion and structural homogenization with the milling time. These results indicate that the cumulative energy input during mechanical alloying leads to phase transformation and facilitates the formation of an FCC-dominant nanocrystalline structure. Also, the results offer useful insights into the energy-controlled mechanisms governing the microstructural evolution of Cantor alloys.