Effect of boron addition to the hard magnetic bulk Nd60Fe30Al10 amorphous alloy

A detailed study of the effect of boron addition to crystallinity, magnetic properties and thermal properties was carried out for alloys Nd60-xFe30Al10Bx with x=0, 1, 3 and 5 produced by copper mold chill casting and melt-spinning. The cast rods of alloys Nd60-xFe30Al10Bx were largely amorphous. Remanence up to 0.154 T and coercivity up to 355 kA/m were observed, which were higher than those of the bulk amorphous Nd60Fe30Al10 rod of the same diameter. A step in hysteresis loop was observed for the hard magnetic cast rod and ribbon melt-spun at a low speed of 5 m/s of the alloys with boron addition. Consistent increase in the amplitude of the step and magnetic field (H) at which the step was observed as the boron content increased. A single magnetic phase with low coercivity was observed for fully amorphous ribbon melt-spun at high speed of 30 m/s. Full crystallization due to heat treatment resulted in transition of hard magnetic amorphous phase of Nd55Fe30Al10B5 cast rod to paramagnetic crystalline phases. TEM results of the as-cast rods illustrated the existence of numerous minute Nd-crystallites in amorphous matrix