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

V. P. Tarasov, Head of Department of Non-Ferrous Metals and Gold, Professor, e-mail: vptar@misis.ru
A. S. Ignatov, Assistant, Department of Non-Ferrous Metals and Gold

The aim of this work is elaboration of compositions of nanostructured hard magnetic materials (HMM) on basis of intermetallic compounds of the rare-earth metals (REM) with the iron-group transition metals, which posses the remanent magnetization (Br) no less than 1.20 T and coercive force (Hci) no more than 720 kA/m. The emphasis of this paper has been on research of correlation between parameters of manufacturing process and actual structure of the high-coercive magnetic materials as well as on optimization of the phase composition of high-coercive nanostructured (HMM) based on nitrogen-containing alloys of REM. One of the basic means of increasing Sm₂Fe₁₇N₃ HMM magnet characteristics is lessening the SmFe₃ and SmFe₂ submagnetic phases content in magnetic medium, but chiefly the α-Fe presence, which leads to a drastic decrease of coercive force. And at the same time, the sole way to influence the process of phases distribution and formation in an ingot of magnetic material is optimization of the Sm₂Fe₁₇ primary alloys melting practice. Optimal phase composition of Sm₂(Fe, Co)₁₇N₃ high-coercive HMM contains no less than 92% of the Sm₂(Fe, Co)₁₇N₃ basic magnet phase and no more than 0.5% of -Fe phase. It has been studied a phase co composition by value of the Sm₂(Fe_0.8Со_0.2)₁₇ alloy ingots, obtained by vacuum induction smelting and the following pouring into metal mould. As a result of the research it has been confirmed that phase composition of Sm₂Fe₁₇ alloys, obtained by inductive smelting, has great heterogeneity which is mostly determined by the cooling rate. Effect of a high-temperature homogenization on the phase compositions of Sm₂(Fe_0.8Со_0.2)₁₇ alloys has been shown. The optimum temperaturetime mode of homogenization has been determined.

This article was written within the implementation of the Agreement on subsidies No. 14.578.21.0037 of July 22, 2014. (Unique identifier of the Agreement: RFMEFI57814X0037) between the National University of Science and Technology “MISiS” and the Ministry of Education and Science of the Russian Federation within the framework of the implementation of the Federal Target Program “Research and Development in the Priority Directions of the Scientific and Technological Complex of Russia Progress for 2014–2020”, approved by the Decree of the Government of the Russian Federation of November 28, 2013, No. 1096.

1. Azzerboni B., Asti G., Pazeti L., Ghidini M. Magnetic Nanostructures in Modern Technology. Dordrecht : Springer, 2008. 345 p.
2. Sun H., Coey J. M. D., Otami Y., Hurley D. P. E. Magnetic properties of new series of rare-earth iron nitrides: R₂Fe₁₇N_у (у = 2, 6). Journal of Physics: Condensed Matter. 1990. Vol. 2. pp. 6465–6470.
3. Nikitin S. A. Magnitnye svoystva redkozemelnykh metallov i ikh splavov (Magnetic properties of rare-earth metals and their alloys). Moscow : Moscow State University, 1989. 248 p.
4. Andreev A. V. Magnitnye i magnitouprugie svoystva monokristallov soedineniy R₂Fe₁₇ (Magnetic and magneto-elastic properties of monocrystals of R₂Fe₁₇ compounds). Fizika magnitnykh materialov : sbornik (Physics of magnetic materials : collection). Under the editorship of D. D. Mishin. Kalinin : State University, 1985. pp. 21–49.
5. Сou X. C. Magnetic anisotropy and magnetic phase transition in R₂Fe₁₇ with R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Tm and Lu. Journal of Magnetism and Magnetic Materials. 1988. Vol. 177. pp. 1002–1007.
6. Coey J. M. D. Rare-earth iron permanent magnets. Oxford : Clarendon Press, 1996. 178 p.
7. Gabay A. M. Hadjipanayis G. C. Stability of PrCo_5+delta and Pr_1–xHf_xCo_5+delta alloys with TbCu₇-type structure at 900–1150 degrees C and their magnetic properties. Journal of Alloys and Compounds. 2011. Vol. 509, No. 5. pp. 2562–2566.
8. Arinicheva O. A., Lileev A. S., Reissner M., Kubel F., Dormi dontov A. G. Effect of Homogenization Temperature on the Structure and Properties of Sintered Magnets Based on Sm(Co, Fe, Cu, Zr)z. Metal Science and Heat Treatment. 2015. Vol. 56, No. 11–12. pp. 595–598.
9. Arinicheva O. A., Lileev A. S., Reissner M., Dormidontov A. G. Effect of heat treatment modes on the structure and magnetic properties of sintered permanent magnets based on Sm(Co, Fe, Cu, Zr)z. Metal Science and Heat Treatment. 2013. Vol. 55, No. 1/2 pp. 63–67.
10. Chaubey G. S., Poudyal N., Liu Y. Z., Rong C. B., Liu J. P. Synthesis of Sm – Co and Sm – Co/Fe nanocrystals by reductive annealing of nanoparticles. Journal of Alloys and Compounds. 2011. Vol. 509, No. 5. pp. 2132–2136.
11. Zhang W. C., Zhao R., Fang Y. K., Zhou M. G., Zhu M. G., Li W. Effect of Sm-rich liquid phase on magnetic properties and microstructures of sintered 2:17-type Sm – Co magnet. Journal of Rare Earths. 2011. Vol. 29, No. 10. pp. 934–938.
12. Diagrammy sostoyaniya dvoynykh metallicheskikh sistem : spravochnik (Constitution diagrams of double metallic systems : reference book). In three volumes. Under the editorship of N. P. Lyakishev. Moscow : Mashinostroenie, 1997. 1024 p.