Research Progress on Grain Boundary Addition Technology for Sintered NdFeB Permanent Magnets

Grain boundary addition technology is a practical process developed to improve the magnetic properties of permanent magnets, which can be seamlessly integrated the production process of sintered NdFeB permanent magnets. At present, the main way to improve the coercivity of NdFeB through grain boundary addition is to add heavy rare earth elements Dy or Tb into NdFeB to improve the anisotropic field. However, the reserves of Dy and Tb are limited, and their prices remain high. Adding a large amount of Dy or Tb will significantly increase the production cost of magnets, there by limiting their widely read application. For the aforementioned reasons, this article compares the effective utilization coefficients of heavy rare earths in binary and multicomponent alloy addition, introduces the principles of grain boundary addition technology for multicomponent alloy addition, proposes replacing traditional binary alloy addition with grain boundary addition multicomponent alloy and summarizes the effects of rare earth Dy/ Tb and Pr/ Nd multicomponent and binary alloy addition on the primary magnet. By comprehensively utilizing high abundance rare earth resources, reducing the proportion of heavy rare earth in alloys and improving the effective utilization efficiency of heavy rare earth. Realization of low cost grain boundary addition for sintered NdFeB to improve magnetic properties.