Entropy Decoding the Fundamental Law of Phase Competition in Glass Formation

The quest to understand the fundamentals of optimal glass-forming compositions in multi-component alloys has long been challenging. To gain insights into the mechanism, a systematic study of glass compositions is conducted using a new strategy of entropy engineering, imposed by the integration of eutectic or intermetallic phases featured by their low melting entropies, which can be determined experimentally and precisely. The optimal composition designed using entropy engineering is further compared with that derived from the conventional “deep eutectic” principle and empirical trial-and-error. For the ternary Cu-Zr-Ti alloys, a series of compositions are achieved, and the ranking of their glass-forming ability indicates a correlation with the melting entropies of initial phases. In particular, the optimal glass-forming composition of Cu_59.99Zr_28.75Ti_11.26 is designed using two initial phases of intermetallic Cu₅₀Zr₅₀ and eutectic Cu_73.5Ti_26.5 with the lowest melting entropies. This designed composition is remarkably equivalent to the reported one, Cu₆₀Zr₃₀Ti₁₀. It is more meaningful that this study uncovers the phase competition mechanism involved in glass formation in a quantitative way for the first time, emphasizing the importance of melting entropies in screening and balancing the competing phases upon glass formation.