New sulfur-bearing Bulk Metallic Glasses: Thermophysical and mechanical properties

近年来，人们发现了一类新的以硫为主要成分的大块非晶合金。到目前为止，硫没有被考虑用于玻璃形成组合物的开发。令人惊讶的是，它表明，含硫的BMG可以产生在一个巨大的组成空间。另外，观察到向现有合金中少量添加硫可导致在从玻璃态加热时热稳定性的改善，从而通过热塑性成形或增材制造产生更好的可加工性。到这一点上，它仍然是开放的，为什么S稳定的亚稳过冷液体（例如在（Ti，Zr）-（Ni，Cu）-S系统），允许形成大块玻璃样品。因此，阐明硫在玻璃形成过程中所起的作用是非常重要的，而硫的作用是由热力学和动力学决定的，为了理解为什么硫能显著改善各种体系的玻璃形成能力和热稳定性，有必要对其热力学和动力学性质进行深入研究。在拟议的项目中，将研究几种含硫合金的热物理性质（如低温粘度、比热容、热力学函数和时间-温度-转变图）。特别地，将检查向商业使用的合金（例如Vitreloy™105（Zr52.5Cu17.9Ni14.6Al10Ti5）、Vitreloy™101（Cu 47 Ti 34 Zr 11Ni 8））中少量添加硫的影响，并与初始的无硫合金进行比较。 该项目的另一个主要课题是研究硫对这些合金机械性能的影响。通常，氧、氮或硫等元素通常被认为是金属玻璃中的杂质，对玻璃形成能力（GFA）和机械性能具有负面影响。因此，我们将研究硫对力学性能的影响，在几个玻璃形成系统相比，无硫alloys.Finally，热物理和力学分析的结果相结合，以验证动力学脆性和机械延展性之间的相关性提出了不同的作者。结合高能同步辐射实验，本研究将对原子结构与宏观性质之间的关系有更深入的了解。这些结果将导致一个全面的了解新的，含硫块体玻璃形成合金及其可能的应用领域。

Recently, a new family of bulk metallic glass (BMG) forming alloys containing sulfur as major constituent has been discovered. Up to now, sulfur was not considered for the development of glass forming compositions. Surprisingly, it was shown that sulfur-containing BMGs can be produced in a vast compositional space. Additionally, it was observed that minor additions of sulfur to existing alloys can lead to an improvement of the thermal stability upon heating from the glassy state resulting in a better processability by thermoplastic forming or additive manufacturing. To this point, it remains open, why S stabilizes the metastable undercooled liquid (e.g. in the (Ti,Zr)-(Ni,Cu)-S system), allowing the formation of bulk glassy samples. Thus, it is important to elucidate the role of sulfur for the process of glass formation, which is governed by thermodynamic and kinetic contributions.In order to understand why sulfur leads to a crucial improvement of the glass-forming ability and thermal stability in various systems, extensive research on their thermodynamic and kinetic properties is necessary. In the proposed project, the thermophysical properties (e.g. the low temperature viscosity, the specific heat capacity, the thermodynamic functions and the time-temperature-transformations diagrams) of several sulfur-containing alloys will be investigated. Especially, the effect of minor additions of sulfur to commercially used alloys (e.g. Vitreloy™105 (Zr52.5Cu17.9Ni14.6Al10Ti5), Vitreloy™101 (Cu47Ti34Zr11Ni8)) will be examined and compared to the initial, sulfur-free alloys. The other main topic of this project is the investigation of the influence of sulfur on the mechanical properties of these alloys. In general, elements like oxygen, nitrogen or sulfur are often considered as impurities in metallic glasses, having a negative influence on the glass forming ability (GFA) and the mechanical properties. Therefore, we will study the influence of sulfur on the mechanical properties in several glass forming systems in comparison to sulfur-free alloys.Finally, the results of the thermophysical and mechanical analysis are combined in order to verify a correlation between the kinetic fragility and the mechanical ductility as proposed by different authors. In combination with high energy synchrotron experiments this study will lead to a deeper insight in the relationship between the atomic structure and the macroscopic properties. These results will lead to a comprehensive understanding of the novel, sulfur-bearing bulk glass forming alloys and their possible fields of application.