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

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 B₆ )_{0.97 - x} Cr_x (TiC)_0.03(x = 0; 0.25; 0.5; 0.75; 1) and (Nd _9.5Fe _84.5B 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, 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 ( ~ 70 wt%) R ₂Fe ₁₄B, the soft phase being ( ~ 30 wt%) alpha-Fe. Mossbauer 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.