Investigation of Rapidly Quenched Rare Earth Iron Alloys for Permanent Magnets

Book excerpt: In early in 1985 the potential of FeNd (Pr) B (SI) alloys for permanent magnet development was demonstrated. The progress under consideration was initiated in April 1983, to study the properties of these materials in more details and in particular to understand the origin of magnetic hardening by correlating the magnetic properties with the microstructure determined by transmission electron microscopy. The magnetic properties of melt-spun Fe-R-B alloys have been examined in the whole rare-earth series. The tetragonal Fe14R2B phase occurs in all alloys studied except in Eu and Yb containing alloys. The Curie temperature of this phase increases from about 170C in Fe14CeB to 375 for Fe14Gd2B and then decreases for the heavier rare-earths and is only 320 C in Fe14Ho2B. In heavy rare-earths, a second phase with a higher Curie temperature approx.(470 C) has also been observed. The nature of this phase is not yet known. The magnetic hysteresis properties of melt-spun Fe-light rare-earth-boron alloys were examined and maximum coercivities were found to scale with the anisotropy fields.