Magnetic properties and microstructure of Fe3B/Pr2Fe14B-type nanocomposite magnets with Co and Cr additions

Abstract Magnetic properties and microstructures of Fe 3 B/Pr 2 Fe 14 B-type nanocomposite magnets have been studied. Increasing content of Pr enhanced the coercivity at the expense of remanence and magnetic energy products in Pr 4+ x Fe 78− x B 18 and Pr 4+ x Fe 76− x Cr 2 B 18 ( x = 0 , 0.5, 1) alloys. Combined additions of Cr and Co further improved hard magnetic properties. Optimum magnetic properties for the Pr 4 Fe 71 Co 5 Cr 2 B 18 alloy with M r (∼1.31 T), H c (∼265 kA/m), (BH) max (∼115.4 kJ/m 3 ) and Pr 5 Fe 70 Co 5 Cr 2 B 18 alloy with M r (∼0.97 T), H c (∼385 kA/m), (BH) max (∼86.2 kJ/m 3 ) were obtained after the samples were annealed at 628 and 658 °C for 10 min, respectively. Partially replacing Pr by Tb improved the overall magnetic properties to M r (∼1.14 T), H c (∼439 kA/m), (BH) max (∼119.4 kJ/m 3 ) in Pr 4 Tb 1 Fe 70 Co 5 Cr 2 B 18 alloy, and also reduced the optimum annealing temperature to 628 °C. Three-dimensional atom probe (3DAP) analysis showed that Cr is strongly partitioned in the Fe 3 B soft phase and Co has higher content in the Pr 2 Fe 14 B hard phase.