Crystallization behavior and magnetic properties of (Nd0.4Pr0.6)9Fe76−Nb B15 (x=0–5) flakes prepared by slow quenching

Abstract (Nd 0.4 Pr 0.6 ) 9 Fe 76− x Nb x B 15 ( x =0–5) flakes were fabricated by slow quenching from master alloys. Effects of Nb on crystallization behavior and magnetic properties of flakes have been systematically investigated. For the sample with x =0, the metastable compound (Nd,Pr) 2 Fe 23 B 3 crystallized as a precursor from amorphous state and then transformated to the (Nd,Pr) 2 Fe 14 B and α-Fe phases, and the (Nd,Pr) 1.1 Fe 4 B 4 phase was formed on further increasing annealing temperature to 700 °C. So the crystallization process of the (Nd 0.4 Pr 0.6 ) 9 Fe 76 B 15 alloy was as follows: amorphous phase (AP)→AP′+(Nd,Pr) 2 Fe 23 B 3 →(Nd,Pr) 2 Fe 14 B+α-Fe→(Nd,Pr) 2 Fe 14 B+α-Fe+(Nd,Pr) 1.1 Fe 4 B 4 . For the sample with x =4, the α-Fe phase was first formed from amorphous matrix, and then the (Nd,Pr) 2 Fe 14 B and Fe 3 B phases subsequently crystallized from residual amorphous phase. So the crystallization process of the (Nd 0.4 Pr 0.6 ) 9 Fe 72 Nb 4 B 15 alloy was as follows: amorphous phase (AP)→α-Fe+AP′ →α-Fe+Fe 3 B+(Nd,Pr) 2 Fe 14 B. The addition of Nb to (Nd 0.4 Pr 0.6 ) 9 Fe 76 B 15 alloy could suppress the formation of the metastable (Nd,Pr) 2 Fe 23 B 3 phase and nonmagnetic (Nd,Pr) 1.1 Fe 4 B 4 phase. Meanwhile, microstructure of (Nd 0.4 Pr 0.6 ) 9 Fe 76 B 15 flakes was significantly refined by introducing Nb. After optimal annealing treatment, the intrinsic coercivity increased from 397.3 kA/m for the Nb-free sample to 1297 kA/m for the 5 at% Nb-doped sample.