Effects of Wheel Velocity and Subsequent Crystallization on the Microstructures

Abstract:

(Nd,Pr)13Fe80Nb1B6 ribbons were melt-spun at 10~35 m/s and subsequently crystallized, the effect of wheel velocity and crystallization conditions on the microstructures and coercivities were studied. The XRD results indicate that the ribbons spun at 10~20 m/s consist of (Nd, Pr)2Fe14B nano-crystalline phase, while the ribbons spun at 25 and 35 m/s are partly and fully amorphous, respectively. In addition, the (004), (006) and (008) peaks of (Nd, Pr)2Fe14B are obvious on the ribbons spun at 18 m/s, suggesting the c-axis anisotropy. The coercivity of the ribbons prepared at 10~25 m/s increases with the increase of wheel velocity, with the maximum of 1216 kA/m at 25 m/s. After the ribbons spun at 25 m/s and 35 m/s are crystallized, the (Nd, Pr)2Fe14B phase and rich-rare earth phase are co-existed. And the coercivities of the ribbons spun at 35 m/s are much higher and with more homogeneous microstructures than those at 25 m/s. The maximum coercivity, 1616 kA/m, is obtained in the ribbons spun at 35 m/s after crystallizing at 973 K for 19 min due to the Pr and Nb addition. Because the Pr2Fe14B has a higher anisotropic coercive field than that of Nd2Fe14B, and the Nb element can inhibit the formation of α-Fe phase and refine the sizes of grains

Key words:wheel velocity; crystallization; coercivity; rich-rare earth alloys