Evolution of local atomic structure during solidification of Fe-RE (RE=La, Ce) alloy

Abstract

For the study of metallic materials, it is vitally important to understand the mechanism involved in the liquid-solid transition in terms of alloying elements. In the present work, the evolution of the short-range order (SRO) of liquid Fe, Fe-La and Fe-Ce systems upon supercooling were investigated using ab initio molecular dynamics simulations. The local structures analyses indicate that the addition of La enhances the glass-forming ability (GFA) of Fe-based alloys by stabilizing the icosahedral SRO, while Ce has no significant effect on it. The effect of Ce on the crystalline nucleation of melting Fe was further examined by isothermal annealing in combination with the analyses of the local bond orientation order parameters. The results reveal that the presence of Ce promotes the formation of the random hexagonal close packing structures during the nuclei formation process, thus helps to reduce the nucleation free energy.