Shear Bands in Amorphous Alloys and Their Role in the Formation of Nanocrystals

The processes of evolution of the structure and surface morphology of Al₈₇Ni₈La₅ and Fe₇₆Si₁₃B₁₁ amorphous alloys under deformation are studied. It is shown that deformation occurs through the formation and propagation of shear bands, which form steps when they reach the surface. The formation of nanocrystals in the shear bands is noted. It is shown that steps on the surface are formed under the combined action of several elementary shear bands. The shear bands have a variable thickness in the range from 5 to 20 nm. An elementary step has a thickness of about 15 nm. The shear bands can be combined into zones. The transverse size of the zones is about 1 μm. The formation of nanocrystals in the zones can lead to anisotropy in the orientational position of nanocrystals in an amorphous matrix. With an increase in the degree of deformation, nanocrystals are formed not only in the shear bands, but also in areas adjacent to them. There is a difference in the kinetics of the formation of nanocrystals in an alloy based on aluminum and iron.