Structure and Magnetic Properties of Nd–Fe–B Magnets Prepared from DyH2-Containing Powder Mixtures

• Published in: Inorganic materials : applied research Vol. 9; no. 3; pp. 509 - 516
• Main Authors: Burkhanov, G. S., Kolchugina, N. B., Lukin, A. A., Koshkidko, Yu. S., Cwik, J., Skotnicova, K., Sitnov, V. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2018; Springer Nature B.V
• Subjects: Annealing; Casting alloys; Chemistry; Chemistry and Materials Science; Coercivity; Composite Materials; Critical field (superconductivity); Dysprosium; Heat treatment; Hydrides; Hysteresis; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Iron; Magnetic properties; Materials Science; Microstructure; Neodymium; Permanent magnets; Phase composition; Powder blending; Praseodymium; Remanence; Restoration; Scanning electron microscopy; Sintering (powder metallurgy); Strip casting; X-ray diffraction; grain-boundary diffusion; low-temperature treatment; dysprosium hydride; coercive force; Nd–Fe–B permanent magnets; strip-casting
• ISSN: 2075-1133; 2075-115X
• DOI: 10.1134/S2075113318030115

Sintered Nd–Pr–Dy–Fe–B permanent magnets were prepared by a powder blending technique using mixtures consisting of strip-casting alloy (wt %) 24.0 Nd, 6.5 Pr, 0.5 Dy, 1.0 B, 0.2 Al, 65.8 Fe and 2 wt % DyH 2 dysprosium hydride. After optimum heat treatment of magnets at 500°C for 1 h, the following hysteretic characteristics were reached: remanence B r = 1.29 T; coercive force j H c = 1309 kA/m; critical field H k = 1220 kA/m; and the maximum energy product ( BH ) max = 322 kJ/m 3 . The characteristic peculiarity of the magnets prepared from hydride-containing power mixtures is the stability of hysteretic properties in the course of subsequent stepped annealings or progressive heatings at temperatures of 250–500°C for, in total, more than 20 h. Conditions of low-temperature annealings resulting in the degradation and subsequent restoration of hysteretic properties of magnets are determined. The evolution of the microstructure and phase composition of magnets in the course of heat treatments was studied by X-ray diffraction analysis and scanning electron microscopy, and the correlation between the structural changes and hysteretic properties of magnets is discussed.