MD simulation on crystallization mechanisms of rapidly supercooled Fe-Ni alloys

Abstract

Abstract A molecular dynamics (MD) simulation has been conducted to investigate the crystallization mechanism during rapid solidification of Fe-Ni alloys. The microstructural evolution is analyzed in terms of the system energy, the pair distribution function (PDF), the largest standard cluster analysis (LSCA), the structure entropy, and visualization. Results indicate that Fe10Ni90, Fe20Ni80, Fe30Ni70 and Fe90Ni10 are rapidly cooled into crystalline solids. The effect of composition of alloys on chemical order of liquid is rather weak, while stronger on solids and Fe20Ni80 has the relative strongest chemical order. Among the Fe10Ni90 alloy, five-fold symmetrical grain boundaries including truncated decahedron atoms hamper the hcp → fcc transition due to their different orientations. But the parallel grain boundaries in Fe30Ni70 is easy covert, resulting in a pathway of supercooled-liquid → (fcc + hcp) → fcc states. Moreover, crystallization is accompanied with the reduction in the number of cluster kinds, the average potential energy, and the structure entropy. In addition, the transformation process of crystal structures at the atomic scale are unveiled by employing the tracing method. These findings will significantly advance the understanding on the crystallization of liquid alloy as well as other metals.