Diffusion processes in hot-deformed Nd–Fe–B magnets with DyF3 additions

• Coercivity enhancement of 19% in Nd–Fe–B magnets without a change in remanence.
• Annealing at 600 °C promotes a strong F diffusion along the flake boundaries.
• Decomposition of DyF3 and interdiffusion of Dy and Nd during hot-deformation is shown by EDX/WDX.

Nd–Fe–B melt spun ribbons have been hot-compacted and subsequently die-upset together with DyF3 in order to increase coercivity in nanocrystalline hot-deformed magnets. Magnetic measurements reveal enhanced coercivities for low and reduced coercivities for high Dy-fractions. This behaviour is due to a superposition of the formation of (Dy,Nd)2Fe14B and non-magnetic Dy and Nd fluoride and oxide phases. Energy dispersive and wavelength dispersive X-ray elemental maps verified this feature. Heat treatments at 600 °C induce a strong F diffusion along the flake boundaries without inducing grain growth. This diffusion is correlated with the changes in magnetic properties.

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