The combined role of nickel and boron on the nucleation and growth of Fe-based non-crystalline alloys

Abstract

Amorphous ribbons of composition Fe 75− x Ni x Si 9B 16 ( x = 1 , 2, 3, 4) were in situ crystallized upon heat treatment and electron beam irradiation. Depending on the Ni concentration an eutectic or primary crystallization took place. The sequence of phases formation was followed by transmission electron microscopy observations and thermal analysis. Other studies (Scripta Metall. 12 (1978) 75, Appl. Phys. Lett. 33 (1978) 233, RQ 111, 1 (1978) 44428) led to the conclusion that the presence of a supersaturated solid solution of boron in Fe-based amorphous alloys strongly influences the crystallization process. In our case, the onset crystallization is determined by the boron solid solution in iron in the case of Ni content less than 3 wt%, while Ni admixtures more than 4 wt% alter the process of the nucleation and the subsequent crystallization. The last one results in the formation of an ultrafine grain structure composed mainly of α-Fe(Si) crystallites. It seems that the modification of the crystallization is a result of the inhibition of the formation of a supersaturated solid solution of boron in iron. An observed large scattering of the values of the lattice parameter of α-Fe(Si) crystallites was ascribed to a different degree of occupation of metalloid atoms in the α-Fe grains.