R-T-B-BASED RARE EARTH SINTERED MAGNET, ALLOY FOR R-T-B-BASED RARE EARTH SINTERED MAGNET, AND METHOD FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an R-T-B-based magnet with high coercive force without increasing a Dy content.SOLUTION: An R-T-B-based rare earth sintered magnet comprises: a rare earth element R; a transition metal T including Fe as an essential element; a metal element M including Al and/or Ga; B; Cu; and inevitable impurities. The R-T-B-based rare earth sintered magnet includes 13.4-17 atom% of R, 4.5-5.5 atom% of B, and 0.1-2.0 atom% of M with the balance consisting of T. The R-T-B-based rare earth sintered magnet is composed of a sintered compact comprising a main phase comprising RFeB, and a grain boundary phase including the rare earth element R more than that in the main phase. The main phase has a direction of magnetization coincident with a c-axis direction. The main phase has a crystal grain which takes an elliptical or oval-shaped form extending in a direction intersecting the c-axis direction. The grain boundary phase includes: an R-rich phase having a total atomic concentration of 70 atom% or more for the rare earth element; and a transition metal-rich phase having a total atomic concentration of 25-35 atom% for the rare earth element.