流变单元与金属玻璃的热力学、力学性质

发布时间：2018-10-19 06:33

【摘要】：大块金属玻璃(BMGs)作为一种新兴的先进材料,与传统材料相比,具有独特的原子结构和优异的性能。在该领域,有待解决的应用瓶颈问题包括:改善材料的塑性,提高玻璃形成能力(GFA),以及降低制作成本。研究非晶合金结构和性能的关系有利于深入了解非晶合金的本质,解决非晶合金材料应用中的瓶颈问题。本研究工作是利用流变单元模型,探究金属玻璃中结构以及性质的关系。虽然有众多不同的理论模型可以用来解释金属玻璃中局部原子结构,但流变单元模型侧重联系局域结构与各项性能之间的关系。随机激活和流变单元的浓度决定了在类似条件下制备得到的金属玻璃的性能。Weibull模量随着体系中流变单元的浓度降低而增加,这一结论增加了该模型的可信度。流变单元在晶化过程中也至关重要。由经典的晶化方程得到的等温晶化数据可以很好的用流变单元模型拟合。它表明了流变单元可能扮演了一种类似晶化前驱体的角色。实验表明非晶合金的晶化焓与流变单元的浓度有很强的关联性。流变单元模型澄清了在形核以及晶粒长大的历程中原子尺度的演化过程。最后,流变单元模型通过结合温度调制的差示扫描量热仪(TMDSC)对可逆吸热过程(玻璃化转变)以及非可逆(弛豫峰)等过程提出了新的解释。玻璃化转变过程依赖于对样品的前处理,但弛豫峰并直接依赖于预处理过程。对可逆与不可逆热流过程的解释也说明了原子在该过程中对体系的反馈以及响应。这些结果有利于深入了解非晶合金的结构和性能的关系,对解决非晶合金材料应用中的瓶颈问题有帮助。
[Abstract]:As a new advanced material, bulk metal glass (BMGs) has unique atomic structure and excellent properties compared with traditional materials. In this field, the application bottlenecks to be solved include improving the plasticity of materials, increasing the glass forming ability (GFA), and reducing the production cost. The study of the relationship between the structure and properties of amorphous alloys is helpful to understand the nature of amorphous alloys and to solve the bottleneck problem in the application of amorphous alloys. In this study, the relationship between structure and properties of metallic glass was investigated by rheological unit model. Although there are many different theoretical models which can be used to explain the local atomic structure in metallic glass, the rheological element model focuses on the relationship between the local structure and the properties. The properties of metallic glass prepared under similar conditions are determined by the concentration of random activation and rheological units. The Weibull modulus increases with the decrease of the concentration of rheological units in the system, which increases the reliability of the model. Rheological units are also important in the crystallization process. The isothermal crystallization data obtained from the classical crystallization equation can be well fitted with the rheological unit model. It suggests that the rheological unit may play a role similar to the crystallization precursor. The experimental results show that the crystallization enthalpy of amorphous alloy is closely related to the concentration of rheological unit. The rheological unit model clarifies the evolution at atomic scale during nucleation and grain growth. Finally, a new interpretation of reversible endothermic process (glass transition) and irreversible (relaxation peak) process is presented by using a differential scanning calorimeter (TMDSC) with a temperature modulated differential scanning calorimeter (DSC). The glass transition process depends on the pretreatment of the sample, but the relaxation peak is directly dependent on the pretreatment process. The explanation of reversible and irreversible heat flux processes also shows the feedback and response of atoms to the system in the process. These results are helpful to understand the relationship between the structure and properties of amorphous alloys and to solve the bottleneck problems in the application of amorphous alloys.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG139.8

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