Influence of a Ta Coating on the Crystallization of Deformed Amorphous Alloys Fe78Si13B9 and Al87Ni8Gd5

The influence of the free volume on the crystallization processes of Fe78Si13B9 and Al87Ni8Gd5 amorphous alloys is studied by X-ray diffraction. To study the influence of the free volume, two methods of amorphous-alloy deformation are carried out: ultrasonic treatment and multiple rolling. After deformation, a protective coating is applied to the amorphous alloys. It is shown that the deposition of a protective coating with a higher vacancy-formation energy compared to that in the amorphous alloys under study is an effective way to maintain the free volume in the amorphous phase, since it is thermodynamically unfavorable for the free volume to migrate from the amorphous phase into the coating material. Experimental data indicate that the preliminary deformation of amorphous alloys leads to an increase in the amount of free volume. An increase in the amount of free volume and its maintenance by the protective coating contributes to the significant crystallization acceleration of Fe78Si13B9 and Al87Ni8Gd5 amorphous alloys. The results obtained expand existing ideas about the processes of the crystallization of amorphous alloys and indicate the possibility of developing materials with different structural characteristics and, consequently, with different physical-chemical properties.