Comparison of Hot-deformation Behavior and Magnetic Properties between Nd-Fe-B HDDR and MQU-F Powder

Hot-deformation behavior of Nd-Fe-B MDR powder was investigated in order to understand the difference in texturing mechanism of HDDR and MQU-F powder during hot-deformation. The composition of the HDDR powder was the same as that of MQU-F powder. However, the grain size of HDDR powder (similar to 300 nm) was eight times larger than that of MQU-F powder (similar to 40 nm). After being subjected to hot-pressing at 700 degrees C under 200 MPa in a vacuum, the grains of the magnets made from HDDR powder and MQU-F powder have globular and platelet shapes, respectively. The remanence was 12.2 kG after die-upsetting process at the strain of 0.5. And it increased up to 13 kG at the strain of 1.4 although the grains still maintained globular-like shapes. The remanence of 13 kG was almost the same as that obtained the magnet from MQU-F powder at the same deformation condition. These results indicate that the hot-deformation behavior is quite different between HDDR and MQU-F powder.