Presentation Information
[P1-22]USE THE HDDR AND GBDP APPROUCHES TO PRODUCE HOT-DEFORMED Nd-Fe-B MAGNETS
*Sujuan Wang1,2,4, Ihor I. Bulyk1,2,4, Heping Zhu1,2,4, Munan Yang1,2,3,4 (1. Jiangxi Province Key Laboratory of Magnetic Metallic Materials and Devices (China), 2. National Rare Earth Functional Materials Innovation Center (China), 3. Ganjiang Innovation Academy, Chinese Academy of Science (China), 4. Jiangxi University of Science and Technology (China))
Keywords:
Nd-Fe-B permanent sintered magnets,Hydrogenation,disproportionation,desorption,recombination,Hot-press,hot-deformation,Fine microstructure,Coercitivity
The hot-press (HP) and hot-deforming (HD) technique (HP-HD) is the proven method for producing bulk magnets. This approach allows the production of fully dense high textured magnets with almost nanoscale microstructure and high coercivity [1]. The grain size of the microstructure of the HP-HD magnets is near nano level, ~100 nm, in one direction only, namely along the pressing direction. The perpendicular grain size is as high as 300 nm. Researchers are working to increase the coercivity of the HP-HD magnets to reach the highest possible value by searching for new approaches for forming finer microstructure.
The combination of the hydrogenation, disproportionation, desorption, recombination (HDDR), the HP-HD and the grain boundary diffusion (GBDP) processes was applied to obtain the bulk magnets with fine microstructure and high magnetic properties. The (Nd,Pr)-(Fe,Ga,Co)-B-type alloy powder produced by MQ company was used as starting materials. The phase composition-pressure-temperature nonequilibrium diagram for the powder-hydrogen system was built at the hydrogen pressure in the range of 10 to 80 kPa and the temperatures up to 950 °C based on data from differential thermal analysis and X-ray diffraction measurements.
The different stages of the HDDR technique were carried out before, during and after HP-HD treatment. The parameters of the HDDR process were chosen based on data about its peculiarities in this powder at low hydrogen pressures and low temperatures. During the HD stage, the hydrogen pressure was below 30 kPa and the temperature was 620-660 °C, and during the DR stage, the temperature was 800-850 °C. The mixture of the (Nd,Pr)-(Fe,Ga,Co)-B and GBDP (Pr,Nd)-Dy-(Cu,Al) alloys powders was used to produce bulk magnets. The HP stage was performed at the temperature of ~670 °C at 180 kPa, and the HD stage was carried out at ~800 °C with 70% deformation. The GBDP treatment was applied after the HP and HD stages.
The material's phase composition and microstructure were studied at every stage of the treatment process.
The dependence of the magnet's properties on the parameters of their production was evaluated. The results clearly indicate that the HDDR-HP-HD-GBDP technique has great potential for producing full density magnets with high magnetic properties.
1. Min Zhao, et al., J. Rare Earths, 41 (2023) 477-488. https://doi.org/10.1016/j.jre.2022.08.007.
The combination of the hydrogenation, disproportionation, desorption, recombination (HDDR), the HP-HD and the grain boundary diffusion (GBDP) processes was applied to obtain the bulk magnets with fine microstructure and high magnetic properties. The (Nd,Pr)-(Fe,Ga,Co)-B-type alloy powder produced by MQ company was used as starting materials. The phase composition-pressure-temperature nonequilibrium diagram for the powder-hydrogen system was built at the hydrogen pressure in the range of 10 to 80 kPa and the temperatures up to 950 °C based on data from differential thermal analysis and X-ray diffraction measurements.
The different stages of the HDDR technique were carried out before, during and after HP-HD treatment. The parameters of the HDDR process were chosen based on data about its peculiarities in this powder at low hydrogen pressures and low temperatures. During the HD stage, the hydrogen pressure was below 30 kPa and the temperature was 620-660 °C, and during the DR stage, the temperature was 800-850 °C. The mixture of the (Nd,Pr)-(Fe,Ga,Co)-B and GBDP (Pr,Nd)-Dy-(Cu,Al) alloys powders was used to produce bulk magnets. The HP stage was performed at the temperature of ~670 °C at 180 kPa, and the HD stage was carried out at ~800 °C with 70% deformation. The GBDP treatment was applied after the HP and HD stages.
The material's phase composition and microstructure were studied at every stage of the treatment process.
The dependence of the magnet's properties on the parameters of their production was evaluated. The results clearly indicate that the HDDR-HP-HD-GBDP technique has great potential for producing full density magnets with high magnetic properties.
1. Min Zhao, et al., J. Rare Earths, 41 (2023) 477-488. https://doi.org/10.1016/j.jre.2022.08.007.