Evolution of short-range order and dynamics of medium-range order influence on the glass-forming ability of CuZrAg alloys

Abstract

The glass-forming ability (GFA) of metallic glasses (MGs) is influenced by both short-range order (SRO) and medium-range order (MRO). However, experimentally examining the dynamic evolution of these microstructures across various time scales remains challenging. Therefore, this study employs molecular dynamics (MD) simulations to investigate the evolution of SRO and relaxation dynamics of MRO impacting on the GFA of Cu60Zr40-xAgx (x = 5, 10, 15, 20, 25) ternary alloys during their rapid solidification process. The GFA is characterized by the width of the supercooled liquid region, with Cu60Zr35Ag5 exhibiting the most prominent GFA among the five alloys. The reverse tracking method was utilized to analyze the inheritance and transformation of defective icosahedral clusters within the SRO. The defective icosahedral heritability and transformation rate are indicative of a more ordered and stable structure, significantly influencing the GFA. Furthermore, the decrease of Ag content leads to the increase of the average size of MRO clusters. The systems with larger MRO nanoclusters exhibit pronounced dynamic heterogeneity and a robust “cage effect”, thus hindering crystallization and promoting GFA. This study approaches GFA analysis from a microstructural evolution and dynamics perspective, aiming to provide theoretical backing for the discovery of alloys with superior GFA.

Keywords

• Molecular dynamics simulation
• Evolution of short-range order
• Dynamics of medium-range order
• Glass-forming ability