# A NOVEL APPROACH FOR SINTERING Nd2Fe14B-, SmCo5- and Sm2Co17-BASED MAGNETS BY THE HDDR PROCESS https://mdr.nims.go.jp/datasets/9bd4edc7-80bf-4315-bc82-bd2472597ea7 ## File - [REPM2025_O3-6_Bulyk.pdf](https://mdr.nims.go.jp/filesets/9ac58e49-1ebd-4078-8fa6-29249fc5bf82/download) ([Detail](https://mdr.nims.go.jp/filesets/9ac58e49-1ebd-4078-8fa6-29249fc5bf82.md)) ## Id 9bd4edc7-80bf-4315-bc82-bd2472597ea7 ## Local identifier ## Visibility open_to_public ## State published ## Created at 2025-08-27T06:45:21.007578Z ## Updated at 2025-09-11T07:31:14.699192Z ## Published at 2025-09-11T07:20:14.263757Z ## Doi https://doi.org/10.48505/nims.5677 ## First published url ## Date published ## Recorded date published ## Resource type conference_presentation ## Manuscript type na ## Collection - id: d28f086a-61aa-4bc7-bcae-5a1078cbc6c7 identifier: https://mdr.nims.go.jp/pid/d28f086a-61aa-4bc7-bcae-5a1078cbc6c7 title: The 28th International Workshop on Rare Earth and Future Permanent Magnets and Their Applications (REPM2025) ## Title - title: A NOVEL APPROACH FOR SINTERING Nd2Fe14B-, SmCo5- and Sm2Co17-BASED MAGNETS BY THE HDDR PROCESS title_type: original lang: en ## Description - description: "The latest approaches to the use of the hydrogenation, disproportionation, desorption, recombination (HDDR) process for the treatment of Nd2Fe14B-type materials, along with new data on the peculiarities of the HDDR method in SmCo5 and Sm2Co17 ferromagnetic materials and application of this method to sinter them are presented. The results indicate that reviving interest in the HDDR technique promises new perspectives for technologies in the field of rare earth permanent magnet materials. The use of the HDDR treatment of Nd-Fe-B materials is well known and started shortly after the discovery of this type of ferromagnetic materials. We propose to use a pressure-composition-temperature diagram for the Nd-Fe-B alloy-hydrogen system to choose the HDDR treatment parameters [1]. Namely, according to the diagram, the parameter values of the HD stage should be shifted towards lower hydrogen pressure and lower temperatures in the range between the temperatures of the start and the end of the disproportionation reaction. The phase composition, microstructure and degree of texture of HDDR-treated sintered Nd-Fe-B magnets were investigated at hydrogen pressures of 10-50 kPa and the disproportionation temperatures of 715-785 °C. It has been shown for the first time that the HDDR technique is a promising way to sinter the Nd-Fe-B type magnets at low temperatures, namely below 850 °C, and to form their very fine microstructure [2]. The influence of the HDDR parameters during sintering on the density, microstructure, degree of texture and magnetic properties of the sintered magnets has been evaluated. The first results of using the modified HDDR approach together with hot pressing, hot deformation and grain boundary diffusion processes to produce permanent magnets are presented. The microstructure and magnetic properties of the magnets have been investigated. A relatively low pressure has been used for HDDR in SmCo ferromagnetic alloys. The HD reaction in the SmCo5-H2 system takes place at a hydrogen pressure of 0.2-0.5 MPa and a temperature of ~560 °C. Disproportionation is complete when the material has been held at the reaction temperature for 2-5 hours. During the DR stage the alloy consists of Sm2Co7, Sm2Co17 and SmCo5 phases, with the highest SmCo5 phase content observed after DR at 950 °C. The first results of sintering SmCo5-type materials by the HDDR route at low temperatures have been presented. The microstructure of these materials is fine, with the grain sizes in the range of 40-140 nm. The porosity of the SmCo5 based alloy is low, less than 1%. The high coercivity of ~50 kOe for the sintered SmCo5-type magnet was achieved by HDDR post-sintering treatment [3].The peculiarities of the HDDR process in Sm2(Co,M)17 alloys, where M=Fe, Ti, V, Nb, have been studied. The influence of the hydrogen pressure during the disproportionation reaction in Sm2Co17-based alloy on the degree of the disproportionation has been determined. It was shown that disproportionation of the Sm2Co17 phase occurs at a pressure of 1.5 MPa. Alloying of the Sm2Co17 alloy with other metals influences the hydrogen pressure during the disproportionation reaction. The HDDR process has been successfully applied to sinter the Sm2Co17-based alloys at low temperatures and form their fine microstructure [4]. The grain sizes of the ferromagnetic phases after HDDR are in the range of 80-140 nm for the Sm2Co17 based alloy. The assumption that the material is textured when it contains remnants of the main ferromagnetic phase has been experimentally demonstrated for of Nd2Fe14B-, SmCo5-, and Sm2Co17- -+type ferromagnetic materials.\r\n\r\n1. I.I. Bulyk, et al., Intermetallics 148 (2022) 107621. https://doi.org/10.1016/j.intermet.2022.107621.\r\n2. I.I. Bulyk and I.V. Borukh, Powder Metall. Met. Ceram., 61 (2023), 657-669. https://doi.org/10.1007/s11106-023-00354-9.\r\n3. I. Bulyk, et al., J. Alloys Compd. 866 (2021) 158272. https://doi.org/10.1016/j.jallcom.2020.158272.\r\n4. I.I. Bulyk and O.P. Kononiuk, Powder Metall. Met. Ceram., 61 (2023) 548-559. https://doi.org/10.1007/s11106-023-00344-x." description_type: abstract lang: en ## Creator - name: Ihor I. Bulyk role: author organization: Jiangxi University of Science and Technology, China - name: RenHui Liu role: author organization: Jiangxi University of Science and Technology, China - name: HePing Zhu role: author organization: Jiangxi University of Science and Technology, China - name: SuJuan Wang role: author organization: Jiangxi University of Science and Technology, China - name: MuNan Yang role: author organization: Jiangxi University of Science and Technology, China - name: Ihor V. Borukh role: author organization: Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine, Ukraine - name: Oleksandr P. Kononiuk role: author organization: Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine, Ukraine ## Contact agent ## Publisher organization: National Institute for Materials Science (NIMS) ## Managing organization ## Keyword - subject: REPM2025 schema: not_defined - subject: Rare earth permanent magnets schema: not_defined - subject: Sintering schema: not_defined - subject: Hydrogenation schema: not_defined - subject: disproportionation schema: not_defined - subject: desorption schema: not_defined - subject: recombination schema: not_defined - subject: Fine microstructure schema: not_defined ## Rights - identifier: https://creativecommons.org/licenses/by/4.0/ ## Other identifier(s) ## Data origin - data_origin_type: other ## Embargo ## Journal ## Conference name: REPM2025 start_date: 2025-07-27 end_date: 2025-07-31 identifier: https://www.nims.go.jp/mmu/repm2025/ ## Related item ## Funding ## Instrument ## Instrument operator ## Instrument managing organization ## Measurement method ## Specimen ## Chemical composition ## Structure for specimen ## Structural feature for specimen ## Specific property for specimen ## Process for specimen treatment ## Computational method ## Energy level/transition state ## Software ## Custom property ## Fileset - id: 9ac58e49-1ebd-4078-8fa6-29249fc5bf82 filename: REPM2025_O3-6_Bulyk.pdf content_type: application/pdf size: 9300690 md5: d3e9e6a9794641590017c4bec85a8dd5 ## Thumbnail fileset_id: 9ac58e49-1ebd-4078-8fa6-29249fc5bf82 filename: REPM2025_O3-6_Bulyk.pdf