非晶合金的结构非均匀性及其与弛豫行为间的关联研究

Metallic glasses show some excellent physical, chemical and mechanical properties, which have attracted widespread attention from both scientists and industrialists. However, lots of basic problems in metallic glasses are still lack of clear understanding and remains challenges, such as the relaxation mechanism, the structure characterization and construction. In current work, serial metallic glasses are selected as model alloy systems. The structure heterogeneity will be characterized by nanoindentation technique and high resolving transmission electron microscopy (TEM). Meanwhile, the non-exponential relaxation behaviors will be investigated by means of dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The distinction of structure heterogeneity caused by the intrinsic property such as the fragility and the evolution of structure result from extrinsic factor such as the thermal annealing will be carefully studied. Furthermore, the impact of both the fragility as well as the thermal annealing upon the non-exponential relaxation will be considered. Based on these results, the correlation between structure heterogeneity and non-exponential relaxation behavior will be established. Finally, this study tries to reveal the underlying physical origin of structure heterogeneity and non-exponential relaxation behavior, which will provide both theoretic foundation and experimental data for the understanding of glass transition and the nature of glass.

非晶合金具有优异的物理、化学和力学性能，已引起了科学界和工业界的广泛研究和关注，然而其中的一些基础问题仍未能得到清晰的理解，如对非晶合金结构的构建表征以及弛豫行为的认知。因此，本项目拟采用典型金属非晶为模型合金，利用纳米压痕新技术和高分辨电镜对其结构非均匀性进行表征，同时借助于动态力学分析仪和差示扫描量热仪等手段对其弛豫行为进行系统研究。系统考察非晶合金体系中本征属性（脆度）引起的结构非均匀性差别和外界因素（热退火处理）导致的结构演化行为，分析脆度以及热退火处理对其弛豫行为的影响，并建立起结构非均匀性与弛豫行为之间的内在关联。同时，尝试揭示结构非均匀性和非指数弛豫的物理起源，为进一步认识玻璃转变现象和玻璃的本质提供理论依据和实验数据。

本项目制备了系列具有低脆度系数的新型铀基非晶合金成分，并开展了其结构弛豫的研究，发现该类非晶体系中的弛豫并不明显；进一步采用纳米压痕仪器研究了不同加载速率与峰值载荷条件下的纳米蠕变行为，依据粘弹性材料的蠕变模型及弛豫谱分析构建出了非晶合金的结构非均匀性模型；最后，并利用相角模式的原子力显微镜获取了其结构非均匀性的实验证据。研究结果表明，铀基非晶合金同常规非晶合金体系一样具有结构非均匀性特征，并且通过成分调制能够显著改变其结构的非均匀性。这些结果对开发具有优异性能的新材料体系具有指导意义，同时有助于非晶合金中结构-性能关系的构建。