Magnetic properties, microstructure and corrosion behavior of Nd10Y1Fe85−xNb3.5Ti0.5Bx (x = 14–22) and Nd10Y1Fe69Nb3.5M0.5B16 (M = Ti, Zr, Cr, Mo) bulk nanocrystalline magnets

The bulk nanocrystalline magnets of Nd10Y1Fe85−xNb3.5Ti0.5Bx (x = 14–22) and Nd10Y1Fe69Nb3.5M0.5B16 (M = Ti, Zr, Cr, Mo) in rod form with a diameter of 1.5 mm were prepared by copper mold injection casting. The magnetic properties, microstructure and corrosion behavior of bulk magnets have been studied. It is shown that the glass forming ability of alloy is obviously improved with increasing the B content. For the Nd10Y1Fe85−xNb3.5Ti0.5Bx (x = 14–22) alloys, the optimal magnetic properties of Br = 6.0 kG, iHc = 7.8 kOe and (BH)max = 6.7 MGOe can be achieved when x = 16, although the sample of x = 22 exhibits better corrosion resistance than the sample of x = 16. For the Nd10Y1Fe69Nb3.5M0.5B16 (M = Ti, Zr, Cr, Mo) alloys, the sample of M = Zr exhibits the best magnetic energy product of (BH)max = 7.0 MGOe, with Br = 6.3 kG and iHc = 8.2 kOe. While, the highest intrinsic coercivity of iHc = 8.8 kOe, with Br = 5.6 kG and (BH)max = 5.8 MGOe is obtained in the sample of M = Mo. The electrochemistry analysis shows that the Zr-doped sample has the best corrosion resistance among the M-doped alloys. The thermogravimetric analysis reveals that the oxidation rates of bulk magnets are significantly enhanced when the temperature is above 350 °C, and the Ti-doped sample has the best antioxidant ability among the M-doped alloys.

► The increase of B content improves the glass forming ability of Nd−Fe−B bulk magnets.
► The increase of B content improves the corrosion resistance of Nd−Fe−B bulk magnets.
► The Zr-doped magnet exhibits the best magnetic properties and corrosion resistance.
► The Ti-doped bulk magnet exhibits the best antioxidant ability.
► The oxidation rate of Nd−Fe−B bulk magnet is enhanced as temperature is above 350 °C.