Effect of wheel speed on phase formation and magnetic properties of (Nd0.4La0.6)-Fe-B melt-spun ribbons

The effect of wheel speed on phase formation and magnetic properties of (Nd0.4La0.6)(15)Fe77.5B7.5 and (Nd0.4La0.6)(13.4)Fe79.9B6.7 ribbons prepared by melt-spinning method was investigated experimentally. Based on X-ray diffraction results, all melt-spun ribbons consist of the main phase with the tetragonal 2:14:1 type structure and the minor alpha-Fe phase. Magnetic measurements show the maximum magnetic energy product ((BH)(max)) and the remanence (M-r) increases firstly and then decreases with the increase of wheel speed, while the coercivity (H-ci) increases, resulting from the variation of the average volume fraction of the alpha-Fe phase and the average grain size in the melt-spun ribbons. Using Henkel plots, the interaction between the 2:14:1 phase and the alpha-Fe phase in the melt-spun ribbons was analyzed and the intergranular exchange coupling is manifested. Optimal magnetic properties of H-ci = 7.27 kOe, M-r = 90.94 emu/g and (BH)(max) = 12.10 MGOe are achieved in the (Nd0.4La0.6)(15)Fe77.5B7.5 ribbon with the wheel speed of 26 m/s. It indicates that magnetic properties of Nd-Fe-B melt-spun ribbons with highly abundant rare earth element La can be improved by optimizing alloy composition and preparation process. (C) 2018 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.