Mechanical alloying in the Co-Fe-Ni powder mixture: Experimental study and molecular dynamics simulation

The formation dynamics of medium- entropy alloy CoFeNi has been studied both experimentally and theoretically in terms of molecular dynamic simulation. The results of experiments and modelling showed good qualitative agreement and supplemented each other. The synthesis was found to occur in two stages. (a) Refinement of crystallites and accumulation of structural defects take place due to severe plastic deformation and friction of metal particles that induce abnormally fast diffusive mixing of different metal atoms. This process results in formation of nanocrystalline intermediate alloy with a crystallite size of about 10 nm. (b) Recrystallization that leads to the nucleation and growth of multicomponent phase with a simple FCC crystal structure. A critical time for the onset of recrystallization depends on planetary milling regime and gaseous atmosphere in the milling jar.