基于热力学与动力学的多元Zr基大块非晶合金的成分设计

Despite the high glass-forming ability the Zr-based bulk metallic glasses possess, stringent conditions such as high vacuum, high-purity raw materials and protection of high-purity argon during fabrication are demanded. This leads to an increase in the cost of production which restricts the large-scale application. Therefore, it is of great scientific and economic significance to develop novel Zr-based metallic glasses with high glass-forming ability and alleviate the sensitiveness to the amount of oxygen and harmful impurities during their formation. By combining thermodynamics and kinetics, the driving force-interfacial energy-viscosity criterion for the quantitative prediction of the glass-forming ability has been put forward in this project, and it is utilized to design the compositions of Zr-(Cu,Ni)-Al-(Y,Gd) alloys. Firstly, the accurate thermodynamic database concerning phase diagrams will be established coupling experimental study, first-principles calculation and CALPHAD (CALculation of PHAse Diagram) method. With this database, the onset driving force for the precipitation of crystalline phases in the quaternary supercooled liquid of different compositions and the interfacial energy between the nucleus and the liquid phase can be calculated. Then, the viscosity database will be built in a similar way to the establishment of the diffusion kinetic database, and the viscosity of different supercooled liquid could be obtained by calculation. Finally, using the driving force-interfacial energy-viscosity criterion, the glass-forming ability of the alloys will be predicted, followed by experimental verification as well as discussions of the influence of thermodynamic and kinetic factors on the glass-forming ability. These would provide a theoretical and experimental basis for the research and development of novel bulk metallic glasses.

Zr基大块非晶合金虽然具有优异的非晶形成能力，但是制备时需要高真空、高纯原材料以及高纯氩气保护的苛刻条件，导致生产成本提高，从而限制了其大规模应用。因此，开发具有较高非晶形成能力的新型Zr基非晶，减轻其形成过程中对氧和有害杂质含量的敏感程度具有重要的科学与经济意义。本项目将热力学与动力学相结合，提出了定量预测非晶形成能力的驱动力-界面能-粘度准则，并用于Zr-(Cu,Ni)-Al-(Y,Gd)合金的成分设计。首先，将实验研究、第一原理计算与相图计算方法相结合建立精确的相图热力学数据库，计算各成分四元过冷液体中晶体相析出的初始驱动力以及晶核与液相之间的界面能。然后，采用同建立扩散动力学数据库相类似的方法建立粘度数据库，计算各过冷液体的粘度。最后，利用驱动力-界面能-粘度准则预测合金的非晶形成能力，并进行实验验证，讨论热力学、动力学因素对其影响，从而为新型大块非晶合金的研发提供理论与实验依据。

Zr基非晶合金具有优异的非晶形成能力，但其制备时需要高真空、高纯原材料和高纯氩气保护，生产成本较高，从而限制了其大规模的生产应用。因此，开发新型Zr基非晶合金，进一步提高其非晶形成能力，最大限度减轻其对氧及杂质含量的敏感程度具有重要的科学与经济价值。本项目围绕非晶形成能力预测准则的建立以及非晶合金成分的高效设计开展了以下工作。首先，本项目首次建立了表征非晶形成能力大小的直接指标临界冷却速率与影响非晶形成能力的热力学因素（驱动力、界面能）和动力学因素（粘度）的组合函数，可用于定量预测合金的非晶形成能力。其次，本项目首次在CALPHAD方法的框架下建立粘度模型，实现了借用扩散动力学计算平台来优化粘度，进而建立粘度数据库。这为预测任一多元体系的粘度提供了便利，也为从动力学角度预测非晶形成能力奠定了基础。再次，通过将实验研究、第一原理计算与相图计算方法相结合建立了Zr-Cu-Gd、Zr-Al-Gd、Zr-Ni-Y、Al-Ni-Y和Zr-Ni-Gd体系的热力学数据库。结合文献报道的边界三元系的热力学描述，建立了Zr-Cu-Al-Y和Zr-Cu-Al-Gd体系的热力学数据库，为从热力学角度预测该多元系的非晶形成能力进而设计新型非晶合金提供了理论指导。最后，基于相图热力学在Zr-Cu-Gd、Zr-Al-Gd、Zr-Ni-Y、Al-Ni-Y和Zr-Cu-Al-Y体系中设计了几组非晶合金成分并进行了实验验证。除Zr-Cu-Gd三元系外，在上述体系中均成功制备出了三元和四元新型非晶合金。这表明热力学因素在非晶合金的形成上虽然不能起决定性作用，但在成分的初始筛取方面仍然起着事半功倍的作用。