Topological Frustration and Glass-Forming Ability of Sulfur-containing Metallic Glass-Formers

含硫金属玻璃形成剂的拓扑挫败和玻璃形成能力

• 批准号: 419370172
• 负责人: Professor Dr. Ralf Busch
• 金额: --
• 依托单位: Institut für Materialphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/419370172?language=en
• 关键词: Topological; Frustration; Glass; Forming; Ability

Very recently, a new family of metallic glasses that contain Sulfur (S) as alloying element has been developed by R. Busch and co-workers. For those alloys, in most cases the glass-forming ability was improved as compared to similar alloy compositions where S was absent. In some cases, the addition of S even served to create the possibility for bulk vitrification for the first time. In that context it is important to recall that Sulfur has a complex coordination behavior and forms more allotropes than any other element, with the S8-ring being the most abundant crystalline allotrope under ambient and near-ambient conditions. In the molten state of pure sulfur, also a large variety of largely different allotropes coexist, including S8-rings, and the occurrence of a helical structure with eight atoms per turn is also known. Thus, conceptually, adding sulfur to a metallic melt increases considerably the topological variability and complexity. In the view of structural models of glass-forming metallic liquids, including early association models, such a situation is prone to vitrification due to geometrical frustration. Thus, the new family of S-containing glass-forming alloys offers the unique opportunity to systematically analyze the impact of a specific alloying element that largely enhances the stability of the liquid state against crystallization. For this systematic study, three distinct groups of alloys with minor -, medium - and high Sulfur content have been identified. If the respective S-free base alloy systems are regarded, the following correlation is observed: bulk metallic glasses with high S-content of 20 at. % or more are related to solid-solution-forming base alloys such as Pd-Ni that do not form glasses at all; medium S-contents below 10 at. % are required to form bulk metallic glasses in base alloys that are marginal glass-formers and minor S additions of the order of a few atomic percent serve to enhance the glass-forming ability (GFA) of base alloys that are already allowing for bulk glass formation even without the addition of sulfur. Thus, the different groups of S-containing and bulk glass-forming alloys allow addressing long-standing and basic issues concerning glass formation in metallic systems in a unique and unprecedented way. We thus propose a systematic and strongly interlinked approach that combines the complementing and long-standing expertise of the three participating groups in research on glass-forming metallic alloys to address the following interconnected questions: - How does sulfur as alloying element modify the viscosity and the atomic mobility of the elemental species in the melt and the glass?- Do the enhanced GFAs of S-containing systems result from a decreased microscopic mobility, from a modified mesoscopic flow behavior or from changed thermodynamic constraints?- How does the S-addition affect the medium-range order of the liquid and the glass?

最近，R。Busch和同事们。对于这些合金，在大多数情况下，与不存在S的类似合金组合物相比，玻璃形成能力得到改善。在某些情况下，S的加入甚至第一次创造了大量玻璃化的可能性。在这种情况下，重要的是要记住硫具有复杂的配位行为，并且比任何其他元素形成更多的同素异形体，其中S8环是环境和近环境条件下最丰富的晶体同素异形体。在纯硫的熔融状态下，还存在大量不同的同素异形体，包括S8环，并且还已知存在每圈具有8个原子的螺旋结构。因此，从概念上讲，向金属熔体中添加硫大大增加了拓扑可变性和复杂性。在玻璃形成金属液体的结构模型，包括早期协会模型，这样的情况是容易玻璃化由于几何挫折。因此，含S的玻璃形成合金的新家族提供了系统地分析特定合金元素的影响的独特机会，该合金元素极大地增强了液态对结晶的稳定性。对于这一系统的研究，已确定了三个不同的组的合金与少，中，高硫含量。如果考虑相应的无S基合金系统，则观察到以下相关性：具有20 at. %或更高的S含量与固溶体形成基础合金（例如Pd-Ni）有关，其根本不形成玻璃; %是在作为边缘玻璃形成剂的基础合金中形成块体金属玻璃所必需的，并且几个原子百分比数量级的少量S添加用于增强基础合金的玻璃形成能力（GFA），所述基础合金已经允许块体玻璃形成，即使不添加硫。因此，不同组的含S和块体玻璃形成合金允许以独特和前所未有的方式解决关于金属系统中玻璃形成的长期存在的基本问题。因此，我们提出了一个系统的和强烈相互关联的方法，结合了三个参与小组在玻璃形成金属合金研究中的互补和长期的专业知识，以解决以下相互关联的问题：-硫作为合金元素如何改变熔体和玻璃中元素物质的粘度和原子迁移率？含硫系统的增强的GFAs是否是由于微观流动性降低、介观流动行为改变或热力学约束改变所致？添加硫如何影响液体和玻璃的中程有序？