A two-step diffusion method for preparing high-performance dual-main-phase sintered mischmetal-iron-boron magnet belongs to the preparing technical field of rare earth permanent magnet materials. The compositions of the two main phase alloys are RE-Fe—B (RE is Nd or Pr) and (Nd, MM)-Fe—B (MM is mischmetal), respectively. First, PrHoFe strip-casting alloy is used as a diffusion source. Next, a PrHo-rich layer is uniformly coated on the surface of (Nd, MM)-Fe—B hydrogen decrepitation powders. The higher anisotropic fields of Pr.sub.2Fe.sub.14B and Ho.sub.2Fe.sub.14B are used to improve the coercivity. Then, the ZrCu strip-casting alloy is used as a diffusion source. A Zr-rich layer is uniformly coated on the surface of the powders after the first-step diffusion, which prevents the growth of the MM-rich main phase grains during the sintering process and the inter-diffusion between the two main phases, thus obtaining high coercivity.

The present disclosure discloses a high-temperature-stability permanent magnet material and an application thereof. The microstructure of the permanent magnet material comprises a first magnetic phase and a second magnetic phase; the first magnetic phase is a magnetic phase with uniaxial anisotropy, and the second magnetic phase is a magnetic phase with spin reorientation transition; and the first magnetic phase and the second magnetic phase are isolated from each other; and the absolute value of the temperature coefficient of saturation magnetization intensity of the first magnetic phase is less than 0.02%/° C. By means of the permanent magnet material comprising the first magnetic phase and the second magnetic phase, a positive temperature coefficient of coercivity can be obtained, so that obtaining a low temperature coefficient of coercivity can be targeted, regular and universal.

A permanent magnet including R and T. R are rare earth elements including Sm and at least one selected from Y and Gd. T is Fe alone or Fe and Co. T maybe partly substituted with M, and M is one or more selected from Ti, V, Cr, Mo, W, Zr, Hf, Nb, Ta, Al, Si, Cu, Zn, Ga and Ge. In a total content of R, Sm content is 60 at % or more and 95 at % or less, and a total content of Y and Gd is 5 at % or more and 35 at % or less. The permanent magnet includes main phase crystal grains having a ThMn.sub.12 type crystal structure.

A sintered R-T-B based magnet includes a main phase formed of an R.sub.2T.sub.14B compound and a grain boundary phase at grain boundaries of the main phase. The grain boundary phase contains an R-T-M compound (M is at least one selected from the group consisting of Ga, Cu, Zn, Al and Si) and an R-M compound. In any cross-section of the sintered R-T-B based magnet, a sum of an area ratio of the R-T-M compound and an area ratio of the R-M compound is not lower than 1.5% and not higher than 3.5%, the area ratio of the R-T-M compound is not lower than 0.4% and not higher than 2.5%, and the area ratio of the R-M compound is not lower than 0.4% and not higher than 2.5%.

The present disclosure is directed to methods of preparing substantially spherical metallic alloyed particles, having micron and sub-micron (i.e., nanometer)-scaled dimensions, and the powders so prepared, as well as articles derived from these powders. In particular embodiments, these metallic alloyed particles, comprising rare earth metals, can be prepared in sizes as small 80 nm in diameter with size variances as low as 2-5%.

A permanent magnet is expressed by a composition formula: R.sub.pFe.sub.qMrCu.sub.5Co.sub.100-p-q-r-s. The magnet includes a crystal grain having a main phase including a TbCu.sub.7 crystal phase, and a volume ratio of the TbCu.sub.7 crystal phase to the main phase is 95% or more.

A sintered magnet body (R.sub.aT.sup.1.sub.bM.sub.cB.sub.d) coated with a powder mixture of an intermetallic compound (R.sup.1.sub.iM.sup.1.sub.j, R.sup.1.sub.xT.sup.2.sub.yM.sup.1.sub.z, R.sup.1.sub.iM.sup.1.sub.jH.sub.k), alloy (M.sup.1.sub.dM.sup.2.sub.e) or metal (M.sup.1) powder and a rare earth (R.sup.2) oxide is diffusion treated. The R.sup.2 oxide is partially reduced during the diffusion treatment, so a significant amount of R.sup.2 can be introduced near interfaces of primary phase grains within the magnet through the passages in the form of grain boundaries. The coercive force is increased while minimizing a decline of remanence.

A sintered R.sub.2M.sub.17 magnet is provided that comprises at least 70 Vol % of a Sm.sub.2M.sub.17 phase, wherein R is at least one of the group consisting of Ce, La, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,

Yt, Lu and Y, and M comprises Co, Fe, Cu and Zr. In an area of the R.sub.2M.sub.17 sintered magnet of 200 by 200 μm viewed in a Kerr micrograph, an areal proportion of demagnetised regions after application of an internal opposing field of 1200 kA/m is less than 5% or less than 2%.

Methods for the production of magnetic powders, compacted magnetic bodies and sintered magnetic bodies. The methods include the use of metal carboxylate precursor compounds such as metal oxalates. The precursor compounds are heated under pressure to form metal alloy particles which can be directly formed into compacted magnetic bodies or can be further refined by using a reductant at elevated temperatures and pressures. The sintered magnetic bodies may have strong magnetic properties even if produced in the absence of a strong magnetic field.

A permanent magnet to be provided to a rotary electric machine. The magnet is expressed by a composition formula: R.sub.pFe.sub.rM.sub.sCu.sub.tCo.sub.100-p-r-s-t. R is selected from rare earth elements, M is selected from Ti, Zr, and Hf, p is a number satisfying 10.5≤p≤12.5 at %, r is a number satisfying 18≤r≤32 at %, s is a number satisfying 0.88≤s≤4.5 at %, and t is a number satisfying 0.88≤t≤13.5 at %. When a proportion r.sub.x of Fe to a total sum of Fe and Co is expressed by r.sub.x=r/(100−p−s−t), a value r.sub.1 of the proportion r.sub.x at a center in a q-axis direction of the magnet and a value r.sub.2 of the proportion r.sub.x at a center in d-axis direction of the magnet satisfy 1.01≤r.sub.1/r.sub.2≤2.