Structural and magnetic engineering of (Nd, Pr, Dy, Tb)-Fe-B sintered magnets with Tb_3Co_(0.6)Cu_(0.4)H_x composition in the powder mixture

摘要

High-coercivity Nd-Fe-B magnets are required for clean energy applications, particularly for hybrid and electric vehicles. This study was focused on the structural design of a Nd_2Fe_(14)B-based magnet by precise engineering of its microstructure, which included grain-boundary diffusion and grain-boundary structuring processes, through the introduction of a hydrogenated Tb_3Co_(0.6)Cu_(0.4)H_x, composition in the powder mixture. A low-rare-earth-metal strip-cast Nd-24.0, Pr-6.5, Dy-0.5, B-1.0, Al-0.2, Fe-balance (wt.%) alloy was used as the base component of the powder mixture. The distributions of the components of the blended powder mixture in the sintered magnet with the added 2 wt% of Tb_3Co_(0.6)Cu_(0.4)H_x, and stability of the structure-sensitive magnetic parameter (coercive force) during a low-temperature heat treatment were studied. The sample exhibited a high coercive force up to 1480 kA/m at a heavy rare-earth element content in the 2-14-1 phase of ～1 at.%.