Production of bulk nanocomposite magnets of an Nd/sub 4/Fe/sub 77.5/B/sub 18.5/ alloy by compression shearing method

Abstract

In this work, the possibility of producing bulk Nd/sub 4/Fe/sub 77.5/B/sub 18.5/ nanocomposite materials by using the compression shearing method is demonstrated. Small amounts of Nd/sub 4/Fe/sub 77.5/B/sub 18.5/ alloy ingots are formed into ribbons by melt spinning. These ribbons are then comminuted into powders which are later consolidated into bulk form by the compression shearing method. X-ray diffraction (XRD), scanning electron microscope (SEM), and a differential scanning calorimeter (DSC) are used to examine the specimen structures. Annealing at temperatures between 773 K and 973 K for 1 h is done for some of the samples. Results show that the bulk amorphous material annealed below the crystallization temperature (773 K) retains an amorphous structure. Annealing between 823 and 923 K results in the formation of metastable Fe/sub 3/B phase together with Nd/sub 2/Fe/sub 14/B phase. However, a higher annealing temperature at 973 K promotes nucleation of the equilibrium /spl alpha/-Fe phase in preference to the metastable Fe/sub 3/B phase. Although the annealed specimens consisted of these phases, a smooth demagnetization curve is revealed indicating that they are nanocomposite magnets with high coercivity.