Production of bulk nanocomposite magnets of an Nd4Fe77.5B18.5 alloy by compression shearing method

In this work, the possibility of producing bulk Nd₄Fe_77.5B_18.5 nanocomposite materials by using the compression shearing method is demonstrated. Small amounts of Nd₄Fe_77.5B_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 Fe₃B phase together with Nd₂Fe₁₄B phase. However, a higher annealing temperature at 973 K promotes nucleation of the equilibrium α-Fe phase in preference to the metastable Fe₃B phase. Although the annealed specimens consisted of these phases, a smooth demagnetization curve is revealed indicating that they are nanocomposite magnets with high coercivity.