Magnetic and microstructural properties of Nd7Fe67B22Mo3Zr0.5Ti0.5 nanocomposite magnets produced by injection casting

The microstructure and magnetic properties of Nd7Fe67B22Mo3.5-xZr0.5Tix (x = 0, 0.5, 1.0) nanocomposite magnets prepared by annealing the amorphous precursors have been investigated and presented. The Nd7Fe67B22Mo3Zr0.5Ti0.5 alloy exhibits high glass forming ability as well as good hard magnetic properties in magnetic rods of 2 mm in diameter and 40 mm in length. As-cast Nd7Fe67B22Mo3Zr0.5Ti0.5 amorphous rod shows soft magnetic properties. Annealing induces promising hard magnetic properties as Br = 0.55 T, iHc = 965 kA/m and (BH)max = 47.6 kJ/m3. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe (27 nm), Fe3B (24 nm) and hard Nd2Fe14B (50 nm) magnetic grains. The single phase hard magnetic characteristics of M-H loop and δM curve yield the existence of strong exchange coupling interactions between the magnetically soft and hard phases.