On The Fragility Of Metallic Glass-forming Liquids

Compared with types of non-metallic materials such as polymers and small molecules, metallic liquids are paid attention to only recently in the field of liquid fragility. The correlation between liquid fragility of alloys and micro/maro -properties in liquids or their corresponding solids, as well as the correlation between liquid fragility and potential energy landscape(PEL), is of great significance for understanding the nature of liquid fragility and the relationship between thermodynamics and dynamics, and then for turning the phenomenological energy landscape into quantification.Here the investigation contents can be divided into three interrelated sections: the correlation between liquid fragility and medium/short-range order structures (chapter three and chapter four); how to predict liquid fragility by the features in PEL (chapter five and chapter six); the introduction of a new fragility definition (chapter seven).The main investigation results, as well as the main contents, have been listed as follow:一. Investigation into liquid fragility of metallic glass-forming liquids and the medium/short-range order structures:1. Analyze the limitations of methods to directly or indirectly calculate fragility parameter, based on the consideration that marginal metallic glasses (MMG) usually have indistinct glass transition and lack supercooled regions. Conclusions: The process to calculate liquid fragility of MMG has been given. According to it, the fragility strength of the typical Al₈₅Ni₁₀Ce₅ alloys has been. calculated and discussed.2. Investigate the characteristics of short/medium-range order structure in Al-based ternary alloys; calculate the fragility parameters of the corresponding metallic glass forming liquids by DSC experiments; discuss the correlation between them as viewed from cluster dynamics.Conclusions: The close relationship between liquid fragility and the stability of medium-range order structure is found on metallic materials: the unstable medium-range order structures lead to large fragility strength. It indicates that the cluster stability in liquids is the controlled key to influence the fragility of supercooled liquids.