INFLUENCE OF QUENCHING RATE AND HEAT-TREATMENT ON THE MAGNETIC-PROPERTIES AND PHASE COMPONENTS OF RAPIDLY QUENCHED FE77.5ND4B18.5 ALLOY

The magnetic properties and phase components of rapidly quenched Fe77.5Nd4B18.5 alloy as a function of quenching rate and heat treatment were studied. X-ray diffraction and thermomagnetic measurements show that the Fe77.5Nd4B18.5 ingot consists of Nd2Fe14B, Fe2B and alpha-Fe. The X-ray diffraction patterns of optimally annealed samples show only metastable Fe3B phase which decomposes into Fe2B and alpha-Fe at T(a) > 850-degrees-C, but the thermomagnetic curves show the presence of the Nd2Fe14B phase. In the sample annealed at 950-degrees-C for 60 min, Nd1.1Fe4B4 appears in coexistence with Nd2Fe14B, Fe2B and alpha-Fe. The Fe77.5Nd4B18.5 alloy is found to have very good glass-forming ability. Samples prepared at quenching rates upsilon-s greater-than-or-equal-to 6.6 m s-1 are amorphous and magnetically soft. Annealing at about 650-670-degrees-C gives the highest coercive field, which is nearly independent of quenching rate.