Radiation-induced nanostructuring of the amorphous alloy
UDC: 544.022.51; 621.039.531
Controlled crystallization of the amorphous alloys is used to create nanostructured materials which can be used in the cladding and fuel elements of nuclear reactors because of the corrosion resistance and the radiation swelling resistance. Structural changes in metallic glasses CoFe3.2Si2.5Mn3.1B15.7 after irradiation by Ar+ ions with energy of 30 keV at 100 – 300°C and post-radiation annealing to a temperature 600°C were investigated by methods of the differential scanning calorimetry, atomic probe microscopy and electron microscopy.
It is shown that irradiation at temperatures below the crystallization temperatures (430 and 548°C) leads to nanostructuring of metallic glass. The nanostructure consists of clusters of 20 – 40 nm in size which are combined into grains of 100 – 150 nm in size. Grains on the surface form parallel strips spaced approximately 1 micron. The nanostructure is a structure of severe plastic deformation which is induced by ion irradiation and extends to a depth of tens microns, significantly deeper than the projective range of ions. Radiation-induced formation of nanostructures is accompanied by the particles of metastable borides Co3B segregation in the volume of glass. These particles disappear after post-radiation annealing with the exothermic effect and return to the X-ray amorphous state. The crystallization heat of the nanostructured glass increases by 30% compared to the crystallization heat of the original non-irradiated glass (as-cast state).
The changing of the ion irradiation temperature can significantly complicate the structural relaxation of metallic glasses in post-radiation annealing. Alloys irradiated at high temperatures can display two glass transition points. This indicates the induced inhomogeneity of the alloy.
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