Understanding the phase structure, magnetic properties and anti-corrosion behavior of melt-spun (La,Y)_2Fe_(14)B alloys

摘要

Aiming to develop the rare earth-iron-boron permanent magnets with high performance/cost ratio, a systematic investigation on the phase structure, microstructure, magnetic properties, and corrosion resistance of melt-spun nanocrystalline (La1-xYx)(2)Fe14B alloys has been carried out. In La based alloys, at least 20 at% Y substitution for La is needed to form hard magnetic 2:14:1 phase. With the increase of Y content, the lattice parameters a, c of 2:14:1 phase decrease and its Curie temperature T-c increases linearly. Y substitution also can effectively enhance the inter-grain exchange coupling and the corrosion resistance of La2Fe14B alloy. The corrosion current density i(corr) decreases from 36.2 mu A/cm(2) to 10.6 mu A/cm(2) in 3.5 wt% NaCl solution with increasing x from 0.2 to 1.0, and all these values are lower than those for nanocrystalline Nd2Fe14B alloy. The hard magnetic properties with maximum energy product (BH)(max) of 2.6 MGOe, remanent polarization J(r) of 0.65 T, and intrinsic coercivity H-cj of 84 kA/m have been obtained in (La0.7Y0.3)(2)Fe14B alloys. Y2Fe14B alloy shows the highest (BH)(max) of 6.8 MGOe, J(r) of 0.88 T, and H-cj of 148 kA/m. This work suggests that La-Y-Fe-B alloys also have the potential for fabricating new and low-cost magnetic materials with performance better than hard ferrites.