| Abstract Scope |
Adding small amounts of alloying elements, such as Al, Ga and Cu, can effectively enhance coercivity in Nd-Fe-B sintered magnets by modifying the Nd-rich grain boundary phase (GBP) and limiting interparticle magnetic coupling. Our phase field simulations indicate that during the post-sinter annealing process, the alloying elements react with the Nd-Fe amorphous phase to form Nd6Fe13(Al,Ga,Cu) (a Nd6Fe13Si-type tetragonal phase) at the grain boundary (GB) of sintered Nd-Fe-B magnets. The elemental constituent, morphology and distribution of the Nd6Fe13i-type phase depends on chemical composition and processing conditions. Further, micromagnetic simulation identifies that the formation of Nd6Fe13Si-type phase depletes Fe and reduces the amount of Nd-Fe soft magnetic GBP, which increases the nucleation field of Nd2Fe14B grain and the magnetic domain pinning field at GB during magnetization reversal. Transformation of Nd-Fe soft-magnetic GBP to Nd6Fe13(Cu, Al, Ga) phase can be leveraged as a practical approach for coercivity enhancement in Nd-Fe-B magnet. |