Investigation of structural evolution in the Cu-Zr metallic glass at cryogenic temperatures by using molecular dynamics simulations.

Abstract

In the present work, investigation of structural evolution of Cu33Zr67 specimen during the cooling process from 2500 down to the 300K, 200K, 150K, 100K, 50K, and 10K has been performed at cooling rate of 5K/ps using molecular dynamics simulation. The pair distribution function (PDF) reveals that Zr‒Zr pair causes the splitting of the first peak of the Cu33Zr67 glass at a lower temperature with an increase in height. Splitting of the first and second peaks supports the presence of the inhomogeneous structure with a statistical average of crystal-like and disordered structural regions in the Cu33Zr67 glass. Voronoi cluster analysis indicated that quasi icosahedral clusters such as < 284 > , < 0285 > , and < 0282 > ; mixed-type cluster such as < 0364 > ; and crystal-like clusters such as < 0446 > are responsible for stabilization of glassy phase at 300K, 200K, 150K, 100K, 50K, and 10K. Similarly, the maximum population of the Cu-centered and Zr-centered < 0286 > quasi icosahedral clusters support the stability of the glassy phase over the studied temperature range. Besides, the maximum population of Cu-centered < 0367 > and Zr-centered < 0364 > , < 0367 > , < 0363 > , and < 0365 > mixed-type clusters and Cu-centered < 0448 > and Zr-centered < 0448 > , < 0445 > , < 0446 > , and < 0444 > crystal-like clusters support the possibility of the presence of intermediate phase of CuZr2 at lower temperatures as observed from PDFs. Mean square displacement (MSD) for the Cu33Zr67 glass shows that the diffusion coefficient of Cu and Zr atoms reduces with decreasing temperature from 300 to 10K. Diversity parameter (d) was found to decrease with decreasing temperature.