National University of Science and Technology MISiS, Moscow, Russia:

V. P. Tarasov, Professor, Head of a Chair of Non-Ferrous Metals and Gold
A. V. Kutepov, Leading Engineer of a Center of Industrial Technologies Engineering
D. A. Kutepov, Engineer of a Center of Industrial Technologies Engineering
O. V. Khokhlova, Engineer of a Chair of Non-Ferrous Metals and Gold, e-mail: hohlova.oksana.v@gmail.com

Magnetic materials largely determine the development of energy-efficient technologies, environmentally friendly modes of transport, household appliances and medical equipment, and electronic instrument. More highenergy permanent magnets are the ones based on rare earth metals (REM). Currently, hard magnetic materials (HMM) based on alloy Pr₁₅Fe_77.8В_7.2 are the most promising for production of permanent magnets for cryogenic systems and components of spacecraft operating at very low temperatures (down to minus 180 ^oC). All rare-earth magnetic materials are obtained by powder metallurgy techniques, one of which operation is compacting (pressing) of fine HMM powders in a texture magnetic field. Currently, the most common method of compacting is a dry compaction. Thus receiving and compacting the HMM powders must be carried out in protective inert atmosphere (nitrogen or argon), since these powders are readily oxidized in air, resulting in a drop in their magnetic characteristics. An alternative is wet compaction where HMM powders are obtained and their compacting is carried out in an inert liquids, providing the better protection of HMM powders from environmental effect. This paper studied the density dependence of the HMM intermediates based on alloy Pr₁₅Fe_77.8В_7.2 by pressing force when wet compacting method in specific range of pressures from 15 to 200 MPa. Wet compaction in the range of unit pressures of 15 to 75 MPa with high accuracy is described by the equation ρ = 0.0594 ln (P/P_cr) + 1, and in the range of 75 to 200 MPa — by the equation lg P = 9.151 lgρ + 3.825. Changing the volume content of HMM powder in the slurry of isopropyl alcohol from 5 to 50%, regression of the calculated density does not exceed 1%, and the critical pressure of compression is in the range from 6287 to 6683 MPa.
This work was carried out within the agreement between the National University of Science and Technology MISiS and Scientific and Production Company “MAGNETON” (Moscow, Russia) No. 1/2015 on 28.07.2015, realized with the financial support; governmental order of the Russian Federation No. 218 on 09.04.2010.

1. Ormerod J. The physical metallurgy and processing of sintered rare-earth permanent magnets. International Rare Earth Conference, ETH Zurich, Switzerland, March 4–8. 1985. pp. 49–68.
2. Rodewald W., Blank R., Wall B., Reppel G. W., Zilg H. D. Production of Sintered Nd – Fe – B Magnets with a Maximum Energy Density of 53 MGOe. Proceedings of the 16th International Workshop on RE Magnes and Their Applications, Sendai, Japan. 2000. pp. 119–126.
3. Gutfleisch O., Willard M. A., Bruck E., Chen C. H., Sankar S. G., Liu J. P. Magnetic materials and devices for the 21st century: stronger, lighter, and more energy efficient. Advanced Materials. 2011. Vol. 23. pp. 821–842.
4. Boltachev G. Sh., Volkov N. B., Kaygorodov A. S. Peculiarities of one-axial quasistatic compacting of oxide nanopowders. Rossiyskie nanotekhnologii. 2011. Vol. 6, No. 9/10. pp. 125–130.
5. Samodurova M. N., Barkov L. A., Ivanov V. A. et al. High-energy treatment of monolithic and powder materials by pressure. Metallurg. 2013. No. 4. pp. 88–93.
6. Savchenko A. G. Magnets Nd – Fe – B and prospective technologies of their production. Scientific and practical seminar “Scientific-technological provision of activity of enterprises, institutes and companies”. Moscow : MGIU, 2003. pp. 113–115.
7. Benabderrahmane С., Berteaud P. Nd2Fe14B and Pr2Fe14B magnets characterization and modelling for cryogenic permanent magnet undulator applications. Nuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2012. Vol. 669. pp. 1–6.
8. Dubynina L. V., Ignatov A. S., Tarasov V. P. Functional properties of fabric magnetic materials with strontium ferrite particle based fillers. Tsvetnye metally. 2015. No. 3. pp. 26–29.
9. Sagawa M. Development and prospect of the Nd – Fe – B sintered magnets. REPM Proceedings of 21st International Workshop on RE Magnets and Their Applications, Bled, Slovenia. Ed.: H. Kaneko, M. Homma, M. Okada. 2010. pp. 183–186.
10. Menushenkov V. P. Structural transformations and coercive force in alloys for constant magnets. Part II. Sintered alloys based on Sm – Co and Nd – Fe — B. Gornyy informatsionno-analiticheskiy byulleten. 2007. Iss. 1. p. 163.
11. Tarasov V. P., Ignatov A. S. Study of homogenization effect on the phase composition of Sm2(Fe, Co)17 alloys. Non-Ferrous Metals. 20016. No. 2. pp. 44–46.
12. Nagata H., Sagawa M. Ideal technology of obtaining of sintered magnets Nd – Fe – B. Material science and metallurgy. Prospective techno logies and equipment. Materials of seminar. Moscow : MGIU, 2003. pp. 105–113.
13. State Standard GOST 25280–90. Metal powders. Method for determination of compressibility. Introduced: 1991–07–01.
14. Тorre C. Berg- und Hüttenmännische Monatshefte. Viena, 1948. 67 p.
15. Agte C., Petrdlik M. Kurs praskove metallurgie. Praha, 1951. 113 p.
16. Zhdanovich G. M. Theory of metallic powders pressing. Moscow : Metallurgiya, 1969. 264 p.
17. Balshin M. Yu., Dvilis E. S., Kachaev A. A. Powder metal science. Moscow : Metallurgizdat, 1948. 332 p.
18. Khasanov O. L. Method of bulk compacting of nano- and polydisperse powders. Tomsk : TPU, 2008. 102 p.
19. Samodurova M. N., Barkov L. A., Mymrin S. A., Ivanov V. A., Dzhigun N. C. Theoretical and Experimental Dependences of Density on the Force of Compaction of Powder Blanks. Vestnik YuUrGu. Metallurgiya. 2013. Vol. 13, No. 1. pp. 150–153.