Anisotropic nanocrystalline rare earth permanent magnet and preparation method thereof

A method for preparing an anisotropic nanocrystalline rare earth permanent magnet,

• the anisotropic nanocrystalline rare earth permanent magnet comprising an RE-Fe—B matrix phase and a second phase, wherein
• the RE-Fe—B matrix phase comprises main phase RE2Fe14B flaky nanocrystallines regularly arranged and an RE-rich phase around main phase grains, the main phase RE2Fe14B flaky nanocrystallines having an average grain size in a length direction of 70 nm to 800 nm, and an average grain size in a thickness direction of 30 nm to 200 nm, and each having a length-to-thickness ratio of greater than 1.2;
• the RE-Fe—B matrix phase comprises a coarse-grained region having a volume fraction of not less than 0.5% and not more than 10%, which is calculated based on a volume of the coarse-grained region and a volume of the anisotropic nanocrystalline rare earth permanent magnet, the coarse-grained region being an equiaxed grain region with a grain size of greater than 500 nm;
• and
• the second phase comprises at least one selected from the group consisting of an M-Cu phase and an M-Cu—O phase, M being Ca, or a combination of Ca and Mg;
• the method comprising the steps of
• S1, mixing an RE-Fe—B magnetic powder with an M-Cu alloy powder to obtain a raw material powder, wherein M is Ca, or a combination of Ca and Mg, the RE-Fe—B magnetic powder comprises at least one selected from the group consisting of an anisotropic magnetic powder and an isotropic magnetic powder, and the raw material powder obtained by mixing comprises at least one selected from the group consisting of an anisotropic raw material powder and an isotropic raw material powder;
• and
• S2, subjecting the raw material powder obtained in S1 to thermal processing, such that the main phase RE2Fe14B flaky nanocrystallines are regularly arranged, to obtain the anisotropic nanocrystalline rare earth permanent magnet.