Method for preparing high-performance neodymium-iron-boron magnet through solid-liquid phase separation diffusion process

Abstract

The invention relates to a method for preparing a high-performance neodymium-iron-boron magnet through a solid-liquid phase separation diffusion process. The magnet attached with the diffusion source is subjected to primary liquid phase diffusion heat treatment, the temperature is higher than the melting point of the auxiliary alloy B and smaller than or equal to 600 DEG C, and the time is 30-80 h; then secondary solid-phase diffusion heat treatment is conducted, the temperature ranges from 800 DEG C to 900 DEG C, and the duration ranges from 0.5 h to 3 h Finally, annealing heat treatment is conducted, the temperature ranges from 400 DEG C to 500 DEG C, and the time ranges from 3 h to 5 h; the magnet is prepared from a main phase alloy A which is RaFe100-a-bBb and an auxiliary alloy B which is RcM100-c, R is Pr20Nd80 or Pr25Nd75 alloy, M is one or more of Al, Cu, Zn, Co and Ni, and a, b and c are weight percentage content * 100 and meet the following conditions: a is more than or equal to 26 and less than or equal to 32, b is more than or equal to 0.9 and less than or equal to 1.1, and c is more than or equal to 55 and less than or equal to 95; and the melting point of the auxiliary alloy B is lower than 600 DEG C.

Description

technical field [0001] The invention relates to the technical field of rare earth magnetic materials, in particular to a method for preparing a high-performance sintered NdFeB magnet by a solid-liquid phase separation and diffusion process. Background technique [0002] NdFeB (NdFeB), as the third generation rare earth permanent magnet material, has excellent magnetic properties and is known as the "magnet king". In recent years, the rapid development of industries such as hybrid electric vehicles and wind power generation has put forward higher and higher requirements for the performance of sintered NdFeB magnets. Using the grain boundary diffusion method, replace Nd with heavy rare earth Tb or Dy to form (Tb / Dy) in the outer layer of the grain 2 Fe 14 B shell is the most common and effective method to improve the magnetic properties of sintered NdFeB. The grain boundary diffusion process can be divided into liquid phase diffusion (diffusion source diffuses from the surf...

AI Technical Summary

Problems solved by technology

The low-melting-point alloy method and the low-melting-point metal-assisted method increase the diffusion depth by increasing the fluidity of the diffusion source, but while increasing the diffusion depth, they inevitably increase the rate of diffusion into the grain, resulting in a high concentration gradient and poor squareness. the problem still exists

CN201710497739.1 adopts a two-step grain boundary diffusion process, and uses a low melting point Dy or Tb ternary alloy thin strip as a diffusion source to prepare a high-performance sintered NdFeB magnet, but it has a large concentration gradient for the diffusion source, and the core-shell structure shell Problems such as layer thickness cannot be effectively solved

However, CN202110533903.6 generates microscopic cracks between the matrix phase and the rare earth-rich phase through cyclic cryogenic treatment. These microscopic cracks can be used as effective channels for grain boundary diffusion and increase the depth of heavy rare earth element grain boundary diffusion, but these cracks will reduce At the same time, cracks will cause internal defects of the magnet, and the defect position is likely to become the nucleation point of the reverse domain during the demagnetization process, resulting in a decrease in the coercive force of the magnet

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