Effect of C on phase evolution, microstructure, and magnetic properties of Pr2Fe14B-type nanocomposites

The phase evolution, microstructure and magnetic properties of melt-spun Pr-rich Pr11Febal.B8-yCy (y = 0-8) and Pr-lean Pr9Febal.TixB11-yCy (x = 0, 2.5 and 4; y = 0-11) ribbons have been investigated intensively. A slight substitution of C for B (y = 2) was proven to be effective in improving the magnetic properties of Pr-rich Pr11Febal.B8-yCy nanocomposites. C atoms prefers to enter 2:14:1 phase. in forming Pr2Fe14(B, C). But the volume fraction of Pr2Fe17Cz, alpha-Fe and 1:2 carbide increases, due to the dissociation of 2:14:1 phase and the suppression of Fe3B phase, with further increase of carbon content. The optimal magnetic properties of B-r = 9.4 kG, H-i(c) = 9.3 kOe, and (BH)(max) = 17.3 MGOe were obtained for Pr11Febal.B6C2.- In contrast, the increase of C substitution in Pr9Febal.Ti2.5B11-yCy (y=0-11) ribbons degrades the B-r, H-i(c), and (BH)(max) monotonically, which is arisen from the increase of vol % of Pr2Fe17Cz and alpha-Fe phases, and the rapid decrease of 2:14:1 phase. In comparison with those of Pr9Febal.B11-yCy (y=0-5.5) ribbons, improved magnetic properties of (BH)(max) =15.3-17.8 MGOe with higher coercivity of H-i(c)=9.7-10.8 kOe have been obtained in Ti-containing Pr9Febal.Ti2.5B11-yCy (y=0-5.5) ribbons. However, in higher Ti concentration Pr9Febal.Ti4B11-yCy ribbons, a slight substitution of C for B (y = 0.5-1) is beneficial in improving the coercivity and magnetic energy product, simultaneously. The optimal properties of B-r = 9.4 kG, H-i(c) = 11.1 kOe, (BH)(max) = 18.0 MGOe and alpha = -0.146 %/degrees C, beta = -0.576 %/degrees C were achieved in Pr9Febal.Ti4B10.5C0.5 nanocomposites.