Nanocomposites and nanomaterials

Zr-based amorphous and nanostructured ribbon 
Sergiienko R.A.1, Shcheretskyi O.A.1, Verkhovliuk A.M.1, Myslyvchenko O.M.2
1 Physico-Technological Institute of Metals and Alloys of the NAS of Ukraine, 34/1, Vernadsky Ave., Kyiv, 03142, Ukraine. 
E-mail: rsruslan17@gmail.com
2Frantsevich Institute for Problems of Materials Sciences of the NAS of Ukraine, 
3 Krzhyzhanovsky Str., Kyiv, 03142, Ukraine.

The creation of materials with an amorphous-nanocrystalline structure is a promising area to date and may solve the problem of high brittleness of amorphous alloys [1, 2]. Amorphous alloys can be converted to an amorphous nanocrystalline state by isothermal treatment at a certain temperature. In this work, isothermal treatment of the Zr65Cu17.5Ni10Al7.5 amorphous alloy ribbon was performed in a vacuum in the temperature interval between the glass transition temperature (Tg) and the crystallization temperature (TX), at different processing modes: 370 ºС - 1 h, 2 h. ; 400 ºC - 5 min, 40 min, 2 h; 410 ºС - 1 h; 420 ºС - 1 min, 30 min, 1 h; 430 ºС - 1 h; 440 ºС - 30 min; 450 ºС - 20 min. The Kolmogorov- Johnson-Methl-Avrami (KJMA) model was used to analyze the kinetics of crystallization in the tested ribbon. According to the KJMA model, the values of Avrami constant n = 2,79; 2.92; 3.28 for the ribbon samples correspond to the growth of crystals in three directions with a fixed number of nuclei. After heat treatment of amorphous ribbon at 420°C for 30 minutes, transmission electron microscopy revealed particles of two types which were separated in the amorphous matrix: nanocrystals of a size not exceeding several tens of nanometers and larger crystalline particles of about 1 micron in size. The calculation of the diffraction patterns showed that the nanocrystals belong to the Zr2Cu phase with the tetragonal lattice (body-centered, S.G. I4/mmm (139)) and the larger particles belong to Zr2Ni with the tetragonal lattice (body-centered, S.G. I4/mcm (140). The phase composition detected by transmission electron microscopy corresponds to the phase composition data obtained by X-ray phase analysis. 

1.	Glezer A.M., Shurygina N.A. Amorphous-Nanocrystalline Alloys. –New York- Boca Raton: CRC Press CISP Taylor & Francis Group, 2018. – 467 p.
2.	Inoue A., Fan C., Saida J., Zhang T. High-strength Zr-based bulk amorphous alloys containing nanocrystalline and nanoquasicrystalline particles// Sci. Technol. Adv. Mat.-2000.-Vol.1 (2).-P. 73-86.