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

Abstract 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 MRE 11− y Fe 79.5 B 8+ y Zr 1.5 (MRE=Nd 0.8 (Dy 0.5 Y 0.5 ) 0.2 , y =0–3) alloys have been investigated. Increasing B concentration leads to the appearance and increase of soft magnetic Fe 3 B 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 MRE 10 Fe 82.5 B 6 Zr 1.5 alloy with MRE 11− y Fe 79.5 B 8+ y Zr 1.5 ( 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/m 3 and good thermal stability have been obtained for MRE 9 Fe 79.5 B 10 Zr 1.5 alloy.