Thermodynamic analysis and modeling of novel ternary Ni-S-based bulk metallic-forming systems

我们建议应用CALPHAD(相图计算)方法来模拟多元金属非晶形成系统的热力学。具有X=Pd、Ti、Nb的新型三元大块非晶形成系统Ni-X-S是本课题研究的重点。与常见的五元BMG构型相比，三元体系相对简单，便于CALPHAD模型的应用。虽然我们的实验研究将包括所有三个Ni-X-S体系的二元和三元组成，但首先将重点放在Ni-Pd-S体系的模拟上，因为从平衡热力学的角度来看，它是一个简单的体系，而且文献中已经有了大量的平衡相实验数据。现有的CALPHAD型模型将被扩展，并将开发新的模型，不仅用于描述热力学稳定相图(二元和三元)，而且还用于描述过冷液体的亚稳状态。我们自己的实验数据将被评估和处理，因此它们可以作为CALPHAD建模和计算的关键输入数据。实验工作包括量热(DSC/DTA、Flash-DSC、MDSC)以及结构和微观结构测试(X射线衍射仪、扫描电子显微镜)。物理性质测量系统(PPMS)也将用于温度低至50K。作为该项目的结果，这将是第一次对三元体系的过冷液体的热力学进行真实的建模，因为我们将用大量真实的实验输入数据来支持我们的拟合。

We propose to apply the CALPHAD (CALculation of PHAse Diagrams) approach to model the thermodynamics in multicomponent metallic glass-forming systems. The novel ternary bulk metallic glass (BMG)-forming systems Ni-X-S, with X=Pd, Ti, Nb are the focus of this project. The relative simplicity of the ternary systems in comparison to the commonly found quinary BMG-formers facilitates the application of the CALPHAD modeling. While our experimental investigations will include binary and ternary compositions for all of the three Ni-X-S systems, emphasis will be given first to the modeling of the Ni-Pd-S system, because it is a simple system in terms of equilibrium thermodynamics and extensive experimental data of the equilibrium phases are already available in the literature. Existing CALPHAD-type models will be extended and new will be developed not only for the description of the thermodynamic stable phase diagrams (binaries and ternary), but also for the thermodynamic description of metastable states of the undercooled liquid. Our own experimental data will be assessed and processed, so they can serve as the crucial input data for CALPHAD modeling and calculations. The experimental work includes calorimetry (DSC/DTA, Flash-DSC, MDSC) and structural and microstructural examinations (XRD, SEM/TEM). A physical property measurement system (PPMS) will also be used for temperatures down to 50 K. As a result of this project, this will be the first time that for ternary systems the thermodynamics of the undercooled liquid down to the glass transition in relation to the competing crystalline phases will be realistically modeled, since we will underpin our fits with a large number of real experimental input data.