Method for preparing neodymium-iron-boron magnet through grain boundary diffusion

Abstract

The invention relates to a method for preparing a neodymium-iron-boron magnet through grain boundary diffusion. The method comprises the steps of providing a neodymium-iron-boron prefabricated magnet;forming a heavy rare earth film on the surface of the neodymium iron boron prefabricated magnet; carrying out heat treatment and tempering treatment on the neodymium-iron-boron prefabricated magnet on which the heavy rare earth film is formed; obtaining a prefabricated body, wherein the prefabricated body comprises a normal shell layer, and a transition layer and an abnormal shell layer which aresequentially coated on the normal shell layer, the content of heavy rare earth in main-phase crystal grains in the normal shell layer is gradually reduced from the edges of the main-phase crystal grains to the central parts of the main-phase crystal grains, and the content of heavy rare earth in main-phase crystal grains in the abnormal shell layer is gradually increased from the edges of the main-phase crystal grains to the central parts of the main-phase crystal grains; and removing the abnormal shell layer to obtain the neodymium-iron-boron magnet. By means of the method, the coercive force of the thicker neodymium-iron-boron magnet can be improved through the grain boundary diffusion method, the adaptability of grain boundary diffusion to the thickness of the neodymium-iron-boron magnet is improved, and the problem that the grain boundary diffusion is limited by the thickness of the magnet is solved.

Description

technical field [0001] The invention relates to the technical field of rare earth permanent magnet materials, in particular to a method for preparing NdFeB magnets by grain boundary diffusion. Background technique [0002] NdFeB magnets have a high magnetic energy product, but their magnetic properties will decrease as the temperature increases. Therefore, in order to improve the high temperature stability of NdFeB magnets, it is necessary to increase their coercive force. At present, the methods to improve the coercive force of NdFeB magnets mainly include grain refinement, adding heavy rare earth elements, and grain boundary diffusion. [0003] Among them, the grain boundary diffusion is to cover the surface of the NdFeB magnet with a thin film containing heavy rare earth, and then heat the magnet to a certain temperature, so that the heavy rare earth element diffuses into the interior of the magnet along the grain boundary of the NdFeB magnet under the action of high temp...

AI Technical Summary

Problems solved by technology

However, due to the limited diffusion depth of heavy rare earth elements in NdFeB magnets, that is, when the NdFeB magnets are thick, the use of grain boundary diffusion can only slightly increase the coercive force of thicker magnets.

Therefore, at present, grain boundary diffusion is mainly used to improve the coercive force of thinner NdFeB magnets (the thickness of the magnet in the direction parallel to the easy axis of magnetization is less than 5mm), which has certain limitations.

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