Composition dependence of magnetic properties of directly quenched Nd–Fe–Ti–Zr–B bulk magnets

Magnetic properties, phase evolution, and microstructure of directly quenched NdyFe97−y−zTi3−xZrxBz (x = 0–3; y = 7–10; z = 14–19) bulk magnets of 0.9 mm in diameter have been investigated. Proper Zr substitution for Ti and appropriate Nd and B contents modify the magnetic phases constitution and refine the grain size from 200–250 nm to 50–100 nm. Consequently, the magnetic properties of the rods are enhanced remarkably from iHc = 6.2 kOe and (BH)max = 5.6 MGOe for Zr-free rods to iHc = 6.7–13.5 kOe and (BH)max = 6.7–8.2 MGOe for Zr-substituted NdyFe97−y−zTi3−xZrxBz rods (x = 0.5–2; y = 8–10; z = 14–16). The optimum magnetic properties of Br = 6.6 kG, iHc = 9.6 kOe and (BH)max = 8.2 MGOe were achieved for Nd9.5Fe72.5Ti2.5Zr0.5B15 alloy.

Research highlightsIn this study, we hereby adopted direct casting method to fabricate the Nd–Fe–Ti–Zr–B magnetic rod with the diameter of 0.9 mm and studied effect of composition dependence on their magnetic properties in detail. The experimental results showed that proper Zr substitution for Ti and Nd and B contents has been found to well modify phase constitution and refine the grain size, and to lead to the enhancement of the magnetic properties of the rods. The attractive magnetic properties of Br = 6.0–6.6 kG, iHc = 6.7–13.5 kOe and (BH)max = 6.7–8.2 MGOe for NdyFe97−y−zTi3−xZrxBz (x = 0.5–2; y = 8–10; z = 14–16) alloys. The magnetic properties of the rods developed in this study are superior to those of the magnets obtained by the annealing of amorphous bulk precursors, reported by other research groups, especially for iHc. The NdyFe97−y−zTi3−xZrxBz (x = 0.5–2; y = 8–10; z = 14–16) alloys obtained by direct casting method represents substantial step to production of isotropic permanent magnets for thin magnets with specific small size and higher temperature applications.