R-Fe-B TYPE SINTERED MAGNET AND METHOD FOR MAKING THE SAME

文件类型：PDF文档
文件大小：1199K
The present invention relates to an R-Fe-B-based sintered magnet containing R_2(Fe, (Co))_14B intermetallic compound as a main phase. The magnet contains boride phases such as Ti, at grain boundary triple junctions but does not contain R_1.1Fe_4B_4 compound phase; and has a core/shell structure which the main phase is covered with grain boundary phases comprising an amorphous and/or sub 10 nm nano-crystalline R-Fe(Co)-M_1 phases or the R-Fe(Co)-M_1 phase and a crystalline or a nanocrystalline and amorphous R-M_1 phase having at least 50 at% of R, wherein R is rare earth element and essentially containing neodymium (Nd) and praseodymium (Pr). A surface area coverage of the R-Fe(Co)-M_1 phase on main phase is at least 50%, and a width of an intergranular grain boundary phase is at least 10 nm and on average at least 50 nm. According to the present invention, the magnet does not contain Dy, Tb and Ho or exhibits a coercivity of at least 10 kOe despite a low or a zero content of Dy, Tb and Ho.