Optimizing The Microstructure Of Low-Rem Nd-Fe-B Sintered Magnet Using Dy3co0.6cu0.4hx Addition

In recent years, the application of various additions (hydrides, oxides, intermetallic compounds, etc.) to powder mixtures for manufacturing Nd-Fe-B magnets shows promise as the method that allows one to increase the hysteretic characteristics of the magnets at the expense of realized grain-boundary diffusion and grainboundary structuring processes. The hysteretic characteristics of sintered Nd-Fe-B magnets are highly sensitive to their microstructure and composition of phases. This paper is focused on the coercivity enhancement of the near-stoichiometric Nd2Fe14B-based magnet by optimizing microstructure, which included processes of grain boundary diffusion and grain boundary structuring via the application of hydrogenated Dy(3)Co(0.6)Cu(0.4)Hx compound added to the powder mixture. The base alloy having the composition Nd-24.0, Pr6.5, Dy-0.5, B-1.0, Al-0.2, Fe-balance was prepared by strip-casting technique and subjected to hydrogen decrepitation during heating to 270 degrees C in a hydrogen flow at a pressure of 0.1 MPa and subsequent 1 h holding at this temperature. Dy3Co0.6Cu0.4 alloy was prepared by arc melting in an argon atmosphere and subjected to homogenizing annealing at 600 degrees C for 90 h. The subsequent hydrogenation under the conditions used for the decrepitation of the strip-cast alloy. The phase composition of Dy3Co0.6Cu0.4 was studied by X-ray diffraction analysis, DTA and scanning electron microscopy, electron microprobe analysis. Additions of the hydrogenated compound to Nd-Fe-B-based sintered magnets allow us to manufacture magnets with Br = 1.34 T and jHc = 1120 kA/m. The microstructure, phase composition and distributions of REM, Co, Cu for the prepared magnets were investigated by SEM/EDX method. Stability of structure-sensitive parameter, namely, the coercive force jHc of the sintered magnet prepared with 2 wt% of Dy(3)Co(0.6)Cu(0.4)Hx addition was studied.