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

Magnetic properties and microstructures of Fe3B/Pr2Fe14B-type nanocomposite magnets have been studied. Increasing content of Pr enhanced the coercivity at the expense of remanence and magnetic energy products in Pr4+xFe78−xB18 and Pr4+xFe76−xCr2B18 (x=0x=0, 0.5, 1) alloys. Combined additions of Cr and Co further improved hard magnetic properties. Optimum magnetic properties for the Pr4Fe71Co5Cr2B18 alloy with Mr (∼1.31 T), Hc (∼265 kA/m), (BH)max (∼115.4 kJ/m3) and Pr5Fe70Co5Cr2B18 alloy with Mr (∼0.97 T), Hc (∼385 kA/m), (BH)max (∼86.2 kJ/m3) 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 Mr (∼1.14 T), Hc (∼439 kA/m), (BH)max (∼119.4 kJ/m3) in Pr4Tb1Fe70Co5Cr2B18 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 Fe3B soft phase and Co has higher content in the Pr2Fe14B hard phase.