EFFECT OF C, AL AND SI ADDITIONS ON THE MAGNETIC-PROPERTIES OF MELT-SPUN ND-FE-B ALLOYS

We have studied the effect of the addition of C, Al or Si on the magnetic properties of Nd-Fe-B-based alloys crystallized from amorphous states. The amorphous Fe77.5Nd15(B1-xMx)7.5 (M = C, Al or Si and x = 0- 1) alloys were prepared using the melt-spinning method. An increase in C content increases the remanence B(r) of Fe77.5Nd15(B1-xCx)7.5 alloys crystallized at 873 K, and the maximum energy product (BH)max is obtained as 93 kJ m-3 in the composition range x = 0.15-0.25. On addition of Al, the coercivity (i)H(c) is at a maximum (1.55 MA m-1) at x = 0.25. It is concluded from the variation of the relative intensities of the Mossbauer spectra that Al or Si atoms are preferentially substituted for one or two (k2 and probably j2) Fe sites in the Nd2Fe14B phase. Mossbauer spectra show that C atoms occupy the same site as B atoms in the Nd2Fe14B phase and give a similar effect to that of B. The average magnetic hyperfine field of Nd2Fe14C is about 93% of that of Nd2Fe14B.