Atomic level simulation of amorphous/nanocrystalline transition behavior in the Fe based amorphous alloys

Abstract

Iron-based amorphous alloys have attracted significant attention from both technological and scientific communities owing to their soft magnetic property. A recent discovery indicates that amorphous alloys have a transition to the nanocrystalline state after annealing, which exhibiting excellent magnetic properties. To explore how the annealing temperature and alloy composition affect the formation of nanocrystals in the Fe-based amorphous alloys, this study employs molecular dynamics simulations. The first step involves creating amorphous models with varying alloy compositions. Subsequently, annealing processes are simulated for amorphous alloys of two different compositions across a range of temperature conditions. Finally, various characterization techniques, including radial distribution function, Honeycutt-Andersen (HA) bonding index, and Voronoi polyhedral index, are used to analyze the resulting amorphous structures. The results show that the Fe78Si15B7 amorphous alloy has a higher tendency to adopt the standard icosahedral structure compared to the Fe74Cu1Nb3Si15B7 amorphous alloy. Moreover, the percentage of icosahedral formation during annealing exhibit a nonlinear relationship with temperature. This suggests that the Fe78Si15B7 amorphous alloy is more predisposed to forming nanocrystals. Additionally, the proportions of both icosahedral and standard icosahedral structures within the amorphous material increase as annealing time is extended.