Effect of High-Pressure Torsion Deformation and Subsequent Annealing on Structure and Magnetic Properties of Overquenched Melt-Spun Nd9Fe85B6 Alloy

The influence of a high-pressure torsion deformation (HPTD) and subsequent annealing on the magnetic properties and phase transformations in the melt-spun Nd9Fe85B6 alloy has been investigated. Because of the low density of nucleation centers and formation of the metastable NdFe7 and Nd2Fe23B3 phases, the crystallization of the nearly amorphous ribbons leads to the non-uniform and coarse Nd2Fe14B grains resulting in the lower values of the coercivity Hc and remanence Br. The HPTD prior to annealing creates numerous α-Fe nanograins, which apparently serve as nucleation sites for Nd2Fe14B. In the ribbons subjected HPTD and annealed at 600 °C, the α-Fe and Nd2Fe14B grains are uniform and fine (13 and 22 nm, respectively) leading to the increase of Hc by 23% and the increase of Br by 16%. Thus, HPTD is a powerful tool for improvement of the magnetic hysteresis properties in the overquenched Nd9Fe85B6.