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.