The solidification products of levitated Fe83B17 studied by high-energy x-ray diffraction

Detailed high-energy x-ray diffraction studies were performed to gain insight into the evolution of phase formation in undercooled Fe83B17 and the mechanism for the stabilization of face-centered cubic (fcc) Fe in the presence of Fe23B6. Fe83B17 solidifies directly into either the equilibrium Fe2B + Fe phases or the metastable Fe23B6 + Fe phases. When formed, the metastable Fe23B6 phase either rapidly transforms into the equilibrium Fe2B phase within the solidification plateau or can persist down to ambient temperature. Here, we detail these different solidification behaviors in a set of thermal cycles taken from one sample and demonstrate the absence of a direct correlation with cooling rate and thermal history. We show that the coherent growth of Fe23B6 and fcc Fe suppresses the allotropic transition from fcc Fe to bcc Fe. The temperature evolution of the phase fractions and lattice parameters is also presented.