Metal-bonded Sm2Fe17-N-type magnets

Abstract

A number of metal-bonded Sm2Fe17-N magnets have been fabricated. These magnets exhibit iHc = 5.1–17.0 kOe, Br = 6.4–8.4 kG, (BH)max=5.0–10.8 MGOe, Tc = 757 K, and ρ=6.2–6.7 g/cm3. Powder metallurgical techniques have been employed with a mixture of powdered Sm2Fe17-N and Zn, Sn, or In. Heat treatment is carried out in the temperature range of 160–450 °C in a N2 atmosphere at pressures ranging from 0–900 psi. The effects of Zn, Sn, and In contents and heat treatment conditions on the magnetic properties have been studied. Zn as the binder significantly enhances the coercivity iHc from 1.8–2.5 kOe for Zn-free magnets to 5–17 kOe for 9–20-wt. % Zn-containing magnets. The Fe-Zn phase, FeZn4, and/or Fe3Zn7, formed during heat treatment, may play an important role in producing a high coercivity. Sn-bonded magnets exhibit significant coercivity, whereas the In-bonded materials do not. The coercivity behavior is discussed in terms of the chemistry of the system.