NUST MISiS, Moscow, Russia:

V. P. Tarasov, Head of the Chair for Non-Ferrous Metals and Gold, Doctor of Technical Sciences, Professor, e-mail: vptar@misis.ru
O. N. Krivolapova, Associate Professor of the Chair for Non-Ferrous Metals and Gold, Candidate of Technical Sciences, e-mail: onk@misis.ru
E. S. Gorelikov, Associate Professor of the Chair for Non-Ferrous Metals and Gold, Candidate of Technical Sciences, e-mail: gorelikoves@misis.ru

At present, magnets based on rare-earth metals are increasingly used: in household appliances and medicine, environmentally friendly transport, electrical and energy-saving technologies. Therefore, research to improve the quality of permanent magnets made of rare-earth metals and technology for their production is relevant. The authors investigated the dependence of the Nd – Fe – B permanent magnets texture distortion degree on the pressing force and their geometric dimensions. It was found that an increase in the size factor l/d (l is theworkpiece height; d is the workpiece minimum transverse size or its diameter) leads to a shift of the optimal specific pressing pressure towards larger values while increasing the texture distortion of compressed workpieces. It was found that when pressing long workpieces with l/d > 1.5, the texture distortion degree increases by 10–12%. An equation describing the dependence of the optimal specific pressing pressure P, which provides the minimum value of the texture distortion degree, on the ratio of the compressed sample dimensions l/d during dry pressing of powders of hard-magnetic materials was derived.
The work was performed with the financial support of the Ministry of Education and Science of the Russian Federation in the framework of fulfillment of obligations under the Grant Agreement dated September 26, 2017 No. 14.578.21.0255 (unique agreement identifier RFMEFI57817X0255).

1. Alymov M. I., Milyaev I. M., Yusupov V. S., Milyaev A. I. Nanocrystalline hard magnetic materials. Advanced Materials and Technologies. 2017. No. 2. pp. 10–18.
2. Skokov K. P., Gutfleisch O. Heavy rare earth free, free rare earth and rare earth free magnets-vision and reality. Scripta Materialia. 2018. Vol. 154. pp. 289–294.
3. Shumkin S. S., Prokifev P. А., Semenov М. Yu. Production of permanent magnets from hard-magnetic alloys using rare earth metals. Metallurg. 2019. No. 5. pp. 37–42.
4. Coey J. M. D. Perspective and prospects for rare-earth permanent magnets. Engineering. 2019. Vol. 6, Iss. 2. pp. 119–131.
5. Takashi M., Hisazumi A. Quantum theory of rare-earth magnets. Journal of the Physical Society of Japan. 2018. Vol. 87. p. 041009.
6. Nagata Kh., Sagava М. The ideal technology for producing sintered NdFeB magnets. Proceedings of the Russian-Japanese seminar “Materials Science and Metallurgy. Advanced technologies and equipment” Moscow : MGIU, 2003. pp. 105–113.
7. Li L., Post B., Kunc V., Elliott A. M., Paranthaman M. P. Additive manufacturing of near-net-shape bonded magnets: prospects and challenges. Scripta Materialia. 2017. Vol. 135. pp. 100–104.
8. Ramlan R., Muljadi M., Sardjono P., Suprapedi S., Setiabudidaya D. et al. Analysis of physical and magnetic properties of hybrid composite magnet system SrFe12O19 – NdFe. AIP Conference Proceedings. 2020. Vol. 2256. P. 030012. DOI: 10.1063/5.0014512.
9. Sonnleitner K., Huber Ch., Teliban I., Kobe S., Sage B. et al. 3D printing of polymer-bonded anisotropic magnets in an external magnetic field and by a modified production process. Applied Physics Letters. 2020. Vol. 116. p. 092403.
10. Sagawa M., Une Y. A new process for producing Nd–Fe–B sintered magnets with small grain size. Proceedings of the 20^th International Workshop on Rare Earth Permanent Magnets and Their Applications. 2008. pp. 103–105.
11. Xia M., Abrahamsen A. B., Bahl C. R. H., Veluri B., Millot S. et al. The influence of carbon and oxygen on the magnetic characteristics of press-less sintered NdFeB magnets. Journal of Magnetism and Magnetic Materials. 2017. Vol. 422. pp. 232–236.
12. Dong S., Li W., Chen H., Han R. The status of Chinese permanent magnet industry and R and D activities. AIP Advances. 2017. Vol. 7. p. 056237.
13. Zhdanovich G. М. Theory of pressing metal powders. Moscow : Metallurgiya, 1969. 264 p.
14. Black J. T., Kohser R. A. DeGarmo’s Materials and Processes in Manufacturing (13-th Edition). Hoboken : John Wiley and Sons, 2019. 896 p.
15. Popov А. G., Shitov A. V., Gerasimov Е. G., Vasilenko D. Yu., Govorkov М. Yu. Obtaining sintered Nd – Fe – B magnets without the process of pressing powders. Fizika metallov i metallovedenie. 2012. Vol. 113, No. 4. pp. 352–362.
16. Magdaleno-Adame S., Cunningham G. J., Miller D., O’Brien S. Calculation of the remnant magnetization and magnetic saturation characteristics for sintered NdFeB permanent magnets utilizing finite element transient simulations. IEEE Transactions on Magnetics. 2019. Vol. 55, Iss 12. p. 2101909.