Composition origin of Cu-Zr bulk metallic glasses understood via a dual-cluster model of binary eutectics

Cu-Zr is an essential binary bulk glass-forming system with the three best bulk metallic glasses at Cu64Zr36, Cu56Zr44, and Cu50Zr50, which are eutectic or near-eutectic compositions. The current study reveals their composition origin by interpreting these eutectics via a dual-cluster model, where a eutectic is composed of two single-cluster-based chemical units derived from the corresponding eutectic phases in simple integer proportions. Each chemical unit represents a stable liquid formulated by the cluster-plus-glue-atom model. For example, eutectic Cu61.8Zr38.2 is deciphered as [Cu-Cu7Zr5]Cu1+4{[Zr-Cu10Zr6]Cu1} = Cu61.6Zr38.4, where the former is from eutectic phase Cu8Zr3 and the latter from another eutectic phase Cu10Zr7. The excellent glass forming composition Cu64Zr36 within this eutectic zone originates from the chemical unit of the Cu8Zr3 phase, [Cu-Cu7Zr5]Cu1 = Cu64.3Zr35.7. Two other eutectics, Cu56.0Zr44.0 and Cu45.7Zr54.3, are also interpreted using this dual-cluster model, leading to suitable glass formers Cu56Zr44 and Cu50Zr50.

Automated summary

This study interprets the three eutectic compositions in the Cu-Zr system and their glass-forming mechanisms using a dual-cluster model.