Effect of Ti-C and Cr Additions on Magnetic Properties of Nanocrystalline (Pr,Nd)-Fe-B Alloys

摘要

The addition of both Ti-C and Cr as grain refiners in Nd-Fe-B nanocomposites substantially increases the coercive field Hc. This motived our investigation of the effect of Ti-C and Cr on Pr-Fe-B nanocomposites. Melt-spun ribbons of composition (Pr$_{9.5}$ Fe$_{84.5}$ B$_{6}$ )$_{0.97 - {x}}$ Cr$_{x}$ (TiC)$_{0.03}({x} = 0; 0.25; 0.5; 0.75; 1)$ and (Nd $_{9.5}$Fe $_{84.5}$B $_{6}$) $_{0.97 - {x}}$Cr $_{x}$(TiC) $_{0.03}$( ${x} = 0.5$ and 1) were produced for study. For a Pr nanocomposite with 1% Cr, ${rm Hc} =$ 12.5 kOe. However, the energy product was limited to 13.6 MGOe by the remanence value. Rietveld analysis of X-ray spectra showed the ribbons to consist of predominantly hard ( ${sim}$70 wt%) R $_{2}$Fe $_{14}$B, the soft phase being (${sim}$30 wt%) $alpha$-Fe. MÖssbauer measurements at 300 K are consistent with a reduced hyperfine field for the hard magnetic phase due to the Cr addition. Analysis of transmission electron microscopy images showed the Pr nanocomposite with 1% Cr to have an increased average grain size.