Optimization of melt spun RE-Fe-B powder composition for fully dense, high energy magnets

Nanocrystalline melt-spun (Nd,Pr)-Fe-B powder can be consolidated into fully dense, anisotropic high-energy magnets by a series of thermo-mechanical processes. The powder composition and processing parameters dictate the magnetic properties of the resulting magnet. More specifically, the alloy must contain a high proportion of the (Nd,Pr)2Fe14B phase for magnetic performance together with a sufficient grain boundary phase to facilitate the grain alignment mechanism during die-upsetting. This paper demonstrates that the type of rare earth component (Nd,Pr) and minor alloy additions (Cu,Ga) have a dramatic effect on the grain boundary phase and ultimately the magnetic properties. A relatively low cost Pr-Fe-B-Cu alloy has been shown to have enhanced room temperature magnetic performance. However, these advantages are offset by the Pr-Fe-B composition having a larger thermal coefficient of Hci and as a result this type of magnet has inferior performance at 180 °C.