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AssigneeShin-Etsu Chemical Co., Ltd.
InventorsKoichi Hirota, Takehisa Minowa, Takahiro Hashimoto, Koji Sato, Kenji Yamamoto
Estimating the term…
Disclosed is a novel thin ribbon of a rare earth/iron/boron-based magnet alloy prepared by quenching of an alloy melt by the method of strip casting, from which a sintered permanent magnet is obtained by the powder metallurgical method. The sintered permanent magnet can be imparted with greatly improved magnetic properties or, in particular, residual magnetic flux density when the thin alloy ribbon as the base material thereof has a metallographic phase structure containing “four-phase regions” consisting of (a) an α-iron phase, (b) a R-rich phase, in which R is a rare earth element selected from praseodymium, neodymium, terbium and dysprosium, (c) a RxT4B4 phase, in which T is iron or a combination of iron and a transition metal element other than iron and rare earth elements and x is a positive number varying with the rare earth element, and (d) a R2T14B phase, in which R and T each have the same meaning as defined above, each phase being dispersed with a grain diameter in a limited range, in a volume fraction of from 1 to 10%.
A thin ribbon of a rare earth-based magnet alloy, having a metallographic phase structure of which the volume fraction of a four-phase region consisting of (a) an α-iron phase having α-iron grains with a grain diameter of 0.1 to 20 μm, (b) an R-rich phase which is a phase richer in the content of rare earth element than in an R2T14B phase, R being a rare earth element selected from praseodymium, neodymium, terbium and dysprosium, said R-rich phase having R-rich grains with a grain diameter of 0.1 to 20 μm, (c) an RxT4B4 phase, in which R has the same meaning as defined above, T is iron or a combination of iron and a transition metal element other than iron and the rare earth elements and x is a positive number larger than 1 varying with the rare earth element, said RxT4B4 phase having RxT4B4 grains with a grain diameter of 0.1 to 10 μm and (d) the R2T14B phase, in which R and T each have the same meaning as defined above, the R2T14B phase having R2T14B grains with a grain diameter of 0.1 to 20 μm, each phase being uniformly dispersed in the four-phase region, is in the range from 1 to 20% by volume, with the proviso that the rest of the volume fraction consists of the R-rich phase, RxT4B4 phase and R2T14B phase or consists of the R-rich phase and R2T14B phase.
Dependencies are inferred from the claim text.