Melt-spun L10 Fe–Pt–(Zr, Nb and Ti)–B nanocrystalline alloys with high coercivity

The additional effect of Zr, Nb and Ti to the melt-spun Fe–Pt–B alloys has been investigated. An L10–FePt nanocrystalline structure with a grain size less than 100 nm and coercivity (Hc) higher then 200 kA/m were obtained for the melt-spun (Fe0.55Pt0.45)–M–B (M = Zr, Nb and Ti) alloys without any annealing treatment. The simultaneous addition of M and B to near equiatomic FePt alloys remarkably decreases the melting temperature to the temperature under the order–disorder transformation temperature of the FePt phase. Therefore, the nanocrystalline L10–FePt phase should be directly synthesized without allowing the formation of the disordered fcc phase during the rapid solidification because the temperature region where the fcc phase is stable does not exist. The low melting temperature that resulted from the addition of M and B, presumably because of the strong interaction of Pt–M pairs, appears to facilitate the formation of the ordered L10 nanocrystalline phase during the rapidly quenching method of the alloy melt.