Comparison of microstructure and magnetic properties of gas-atomized and melt-spun MRE-Fe-Co-M-B (MRE=Y+Dy+Nd,M=Zr+TiC)

An MRE2 (Fe,Co)14 B alloy with Zr substitution and TiC addition was systematically studied. It was found by means of X-ray diffraction, transmission electron microscopy (TEM) and magnetic measurements that the combination of Zr substitution and TiC addition yields adequate microstructural control in both gas atomization (GA) and melt spinning (MS) techniques. For MS ribbons, an Hcj of 11.7 kOe and (BH)max of 11.9 MGOe at 27 °C were obtained in the ribbons spun at 16 ms and annealed at 700 °C for 15 min. For GA powders, an Hcj of 9.1 kOe and (BH)max of 9.2 MGOe at 27 °C were obtained in 20-25 μm GA powder annealed at 700 °C for 15 min. The temperature coefficients of Br and Hcj are 0.06 and 0.36%°C for the MS ribbon and 0.09 and 0.4%°C for the GA powder in the temperature range of 27-100 °C, respectively. TEM images revealed that the MS ribbon consists of a fine and uniform microstructure with an average size of 30 nm, while the GA spherical powder consists of an interior coarsened microstructure with a grain size of 80 nm and a rim area with a grain size of 10 nm.