Effect of added Cu on the Nd-rich phase in hot-deformed NdFeB magnets

It is found that the addition of Cu to NdFeB magnet material changes the composition of the grain-boundary phase from NdFe based phase to binary NdCu. It is also found that when the grain boundary phase is liquid, it can dissolve significant amounts of the 2-14-1 phase, and when liquid phase is extruded from the sample during deformation, the 2-14-1 phase is transported outside the original sample volume. During cooling, grains of the 2-14-1 phase nucleate and grow from the liquid. This process provides clear evidence that the constituents of 2-14-1 phase can be transported by liquid diffusion in the grain boundary phase at elevated temperatures