Compositional optimization for nanocrystalline hard magnetic MRE–Fe–B–Zr alloys via modifying RE and B contents

To reduce the rare earth content and maintain good magnetic properties for NdFeB based alloys, the effects of RE and B contents on the micro-structure and magnetic properties of nanocrystalline MRE11−yFe79.5B8+yZr1.5 (MRE=Nd0.8(Dy0.5Y0.5)0.2, y=0–3) alloys have been investigated. Increasing B concentration leads to the appearance and increase of soft magnetic Fe3B phase and reduced grain size. With decreasing MRE and increasing B concentrations, the coercivity decreased from 1159.8 kA/m for y=0 to 619.0 kA/m for y=3. The saturation magnetization and remanence increased with B content until y=2 then decreases. The B content also has effects on the exchange coupling, microstructure and thermal stability. While comparing MRE10Fe82.5B6Zr1.5 alloy with MRE11−yFe79.5B8+yZr1.5 (y=1 and 2) alloys, the alloy with 9 at% MRE can achieve similar magnetic properties as that with 10 at% MRE. The magnetic properties with coercivity of 792.2 kA/m, (BH)max of 128 kJ/m3 and good thermal stability have been obtained for MRE9Fe79.5B10Zr1.5 alloy.

• Nanocomposite NdFeB composition is optimized to reduce RE from 10 to 9 at.%.
• Increasing B content benefits microstructure, exchange coupling, thermal stability.
• Alloy with 9% RE has Hc=792kA/m, (BH)max=128kJ/m3 and low temperature coefficients.