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ArticleName The influence of gallium and copper on the corrosion properties of magnetically hard materials of the Nd – Fe – B system
DOI 10.17580/tsm.2018.07.02
ArticleAuthor Gorelikov E. S., Tarasov V. P., Kutepov A. V., Osipenkova A. A.

National University of Science and Technology “MISiS”, Moscow, Russia:
E. S. Gorelikov, Deputy Director, Center for Engineering of Industrial Technologies, e-mail:
V. P. Tarasov, Professor, Head of Department Non-ferrous Metals and Gold
A. V. Kutepov, Principal Engineer, Center for Engineering of Industrial Technologies
A. A. Osipenkova, Post-Graduate Student, Department of Non-ferrous Metals and Gold


the low resistance to corrosion. One of the promising areas of research in the field of permanent magnet modification is the search for elements whose addition to Nd – Fe – B alloys contributes to increased corrosion resistance. In the work, the permissible value of gallium (Ga) and copper (Cu) content in rare earth magnets was determined, which on the one hand positively affects the corrosion resistance of magnetically hard materials (MHM), and on the other hand will allow realizing the required magnetic characteristics. On the received samples of MHM of basic structure (32% Nd, 0.5% Al, 4% Co, 1.1% B, rest — Fe), the magnetic characteristics (residual induction Br, coercive force by induction Hc b, the coercive force with respect to the magnetization jHc, the temperature coefficient of induction of TCR) and the relative fraction of the total corrosion area of the samples after the corrosion tests within 120 hours of the content of gallium and copper additives from 0.2 to 1 wt. %. It is shown that the most positive effect on the corrosion resistance of MHM samples made of base alloy is the introduction of copper, so in MHM with 1 wt. % Cu corrosion resistance is higher than that of MHM with 1 wt. % Ga by almost 25%. This can be explained by the influence of copper on the phase composition of MHM that is, reducing the amount of boroncontaining phase prone to active oxidation RFe4B, which leads to increased corrosion resistance. It has been found that the introduction of copper into MHM causes a decrease in the residual induction Br, but increases the temperature stability of MHM, by decreasing the TCR and increasing jHc. It is determined that the optimal copper content in MHM with a reduced cost price is 0.6 wt. %.
The work was carried out with the financial support of the Ministry of Education and Science of the Russian Federation in the framework of fulfilling the obligations under the Grant (No. 14.578.21.0255). Agreement from September 26, 2017 (the unique identifier of the agreement RFMEFI57817X0255).

keywords Hard magnetic materials, Nd – Fe – B magnets, corrosion resistance, coercive force, residual induction, temperature coefficient of induction, alloying, gallium, copper

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