Nano size clusters indicating precursor of intermetallic compounds in the supersaturated Fe99Y1 and Fe99Zr1 melt-quenched alloys

Local structures around Y and Zr solutes in bcc-Fe are studied for the melt-quenched ribbons by X-ray absorption fine structure (XAFS). The melt-quenched ribbons of Fe99Y1 and Fe99Zr1 are confirmed as a super-saturated solid solution by X-ray diffraction and DSC. XAFS results indicate that the local structures around Y and Zr for the melt-quenched Fe99Y1 and Fe99Zr1 are similar to those for the Fe-rich intermetallic compounds; Fe17Y2 for Fe99Y1 and Fe2Zr for Fe99Zr1. Prior to the apparent precipitation of the intermetallic compounds by annealing, the precursor of intermetallic compounds, about 1 nm in a diameter, are formed in the melt-quenched Fe99Y1 and Fe99Zr1. The large size mismatch of the atom between solutes (Y and Zr) and host (Fe) is responsible for it. This result shows a sharp contrast to that for the case of Cu and Ga in bcc-Fe, in which Cu and Ga occupy a substitutional site of bcc-Fe.