Enhancing the coercivity of Nd-Cu-diffused Nd-Fe-B permanent magnets by Nb-assisted grain boundary pinning
M. B. Siva Kumar, D. Prabhu, M. Sadhasivam, B. Manjusha, N. Chandrasekaran, K.G. Pradeep, G. Sundararajan, R. Gopalan
Abstract
We report the effect of grain boundary diffusion of the Nd-Cu eutectic phase and the influence of Nb on the microstructure and magnetic properties of Nd-Fe-B melt-spun ribbons. The Atom probe tomography analysis indicated the presence of Nb clusters (∼10 nm), which possibly restricts grain growth during diffusion annealing while facilitating Nd-Cu grain boundary decoration. Correspondingly, the coercivity was enhanced from the initial 1.2 T of the as-prepared to 2.1 T for the 20 wt.% Nd-Cu diffusion annealed (600°C, 2 h). Incidentally, the as-diffused sample exhibited a high coercivity of ∼1 T at 150°C, making it suitable for high-temperature applications.