Effect of refractory boride particles on crystallization of the amorphous alloy Fe85B15

We have studied the characteristic features of the process of transition fr om the amorphous to the crystalline state in the presence of refractory bor ide particles of different crystallographic types (zirconium diboride ZrB2 and lanthanum hexaboride LaB6), introduced into ribbons of Fe85B15 amorphou s alloy directly during ribbon formation. ZrB2 particles in the base alloy have practically no effect on its thermal stability, defined by the tempera ture of onset of formation of primary alpha -Fe crystals, while in the pres ence of LaB6 particles the thermal stability is considerably reduced. This qualitatively correlated with the Dankov principle of structural and dimens ional 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 alpha -Fe crystallization centers is rapid chemical reaction within the zone where they come in conta ct 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 th ermal stability of the base amorphous alloy.