Grain boundary restructuring of the (Misch Metal, Nd)-Fe-B sintered magnet using Pr82Co18 powders

Abstract

The Pr82Co18(wt.%) alloy powders are added to (MM0.5Nd0.5)-Fe-B magnets (MM = Misch Metal) as a variable by grain boundary restructuring to address the problem of low remanence (Br) and coercivity (Hcj) in the magnets. The Hcj of the magnet increases by 96.2% (from 5.54 to 10.87 kOe) when the content of Pr82Co18 alloy powders varies from 0 to 7 wt.%. The microstructural analyses show that the content of the Pr82Co18 alloy powders facilitates the formation of continuous grain boundary layers in the magnets. The improved microstructure effectively blocks the short-range exchange coupling between adjacent grains and creates Pr-rich strongly anisotropic layers in the grains. The synergistic effect of these two factors improves the Hcj. Furthermore, the uniform distribution of the Co element in the matrix phases promotes the formation of the RE2(FeCo)14B (RE = rare earth) phases with higher saturation magnetization of the magnet. Compared with previous research results, it overcomes the disadvantage that the main phase reduction caused by grain boundary restructuring is unfavorable to Br. The MM-Fe-B magnets with high Br and Hcj are prepared, which provides a new prospect for the application of misch metal.