Crystallization of nickel-niobium alloy under deformation and pressure
A paper by Kazan Federal University has been made available in early access in Journal of Non-Crystalline Solids.
A computer experiment made it possible to determine the threshold pressure value; stepping over it leads to an “explosive” crystallization of this alloy.
The work was part of Russian Science Foundation-supported grant project ‘Theoretical, simulation and experimental studies of the physical and mechanical features of amorphous systems with inhomogeneous local viscoelastic properties’ (headed by Professor Anatolii Mokshin).
Nickel-based amorphous metal alloys, as he says, are among the promising materials in terms of their practical application in a wide variety of fields, including microelectronics and mechanical engineering.
“Among such alloys, it is worth highlighting the amorphous metal alloy Ni62Nb38, which is a promising structural material due to its high strength, corrosion resistance and hardness. These properties largely depend on the stability of the amorphous structure, which, in fact, is the structure of a ‘frozen’ melt, liquid,” adds Professor Mokshin.
As a result of computer modeling (molecular dynamics), the researchers found that the stability of the amorphous structure of the Ni62Nb38 alloy is disrupted under mechanical influences: high pressure and shear deformation.
“Shear deformation and high pressures lead to the the formation of crystalline inclusions. The higher the applied pressure, the faster the crystals grow. At high pressures, the material completely loses its useful structural properties,” explains first co-author, Associate Professor Bulat Galimzyanov.
Ni62Nb38 alloy is capable of retaining useful functional properties at pressures not exceeding 400 gigapascals. In comparison, this pressure is four million times the normal atmospheric pressure.
“Exceeding the threshold pressure leads to rapid crystallization of the material. Moreover, during crystallization, two fractions are formed, consisting of Ni and Nb atoms. The growth rate of these fractions differs due to the different concentrations of Ni and Nb atoms,” comments second co-author, senior year student Maria Doronina.
Studies of amorphous alloys and their properties in various conditions lead to a better understanding of their usefulness in practical applications.
The paper was made available online on 4 August 2021 and is set to appear in print in November 2021.
Excellent glass former Ni62Nb38 crystallizing under combined shear and ultra-high pressure
https://www.sciencedirect.com/science/article/pii/S0022309321004658
Source text: Media Center
Translation: Yury Nurmeev