Effect of Refractory Boride Particles on Crystallization of the Amorphous Alloy Fe85B15

Abstract

We have studied the characteristic features of the process of transition from the amorphous to the crystalline state in the presence of refractory boride particles of different crystallographic types (zirconium diboride ZrB₂ and lanthanum hexaboride LaB₆), introduced into ribbons of Fe₈₅B₁₅ amorphous alloy directly during ribbon formation. ZrB₂ particles in the base alloy have practically no effect on its thermal stability, defined by the temperature of onset of formation of primary α-Fe crystals, while in the presence of LaB₆ particles the thermal stability is considerably reduced. This qualitatively correlates with the Dankov principle of structural and dimensional correspondence considered in the theory of heterogeneous nucleation. We have shown that the major factor determining the high catalytic activity of LaB₆ particles with respect to nucleation of α-Fe crystallization centers is rapid chemical reaction within the zone where they come in contact with the Fe₈₅B₁₅ melt. The ZrB₂ particles which do not enter into such a reaction, do not affect the course of crystallization processes and the thermal stability of the base amorphous alloy.