Development and Characterization of Eutectic V-Si-B Alloys with Advanced Specific Mechanical Properties for High Temperature Applications: Role of the New V8SiB4 Phase

V-Si-B合金在高温结构应用中具有巨大的潜力。在第一个资助期内，开发并研究了富V V-Si-B系统的相图，包括液相线投影和1400 °C等温截面。在这些研究中，一个新的三元相，V8 SiB 4被发现，其晶体结构被确定相结合的实验结果和密度泛函理论计算。根据文献和我们自己的结果的当前状态，可以假设V8 SiB 4相的形成温度在V5 SiB 2相的1400 °C和1600 °C之间的范围内。这似乎是从V5 SiB 2相的转变。此外，在25 °C至1000 °C的温度范围内研究了Vss− V3 Si − V5 SiB 2和Vss− V5 SiB 2共晶合金的机械性能。该后续提案的主要目的是研究新V8 SiB 4相的相稳定性取决于温度和合金组成。将使用粉末冶金（PM），即机械合金化和烧结（FAST）生产单片V8 SiB 4相。为了确定V8 SiB 4相的溶解度范围，将制备并研究2-3种新相化学计量略有变化的变体。此外，将进行EDX和/或WDX测量以缩小溶解度范围。随后，将扩大上一项目期间创建的V-Si-B数据库（FactSage），以纳入最新调查结果。作为拟议项目的第二个重点，将在微观和宏观尺度上研究V8 SiB 4相的力学行为。V8 SiB 4和V5 SiB 2相将通过纳米压痕和电子显微镜进行研究，以表征作为晶体取向的函数的变形机制和机械性能。在宏观尺度上，将在900 °C和1000 °C下测试多晶V8 SiB 4和V5 SiB 2相的压缩屈服强度和抗蠕变性。然后将确定的两个金属间相的机械参数应用于模型中，以描述来自第一资助期的合金的变形参数。

V-Si-B alloys have great potential for high-temperature structural applications. In the first funding period the phase diagram including the liquidus projection and the isothermal section at 1400 °C were developed and investigated for the V-rich V-Si-B system. In these investigations, a new ternary phase, V8SiB4, was discovered, whose crystal structure was determined by combining experimental results and density functional theory calculations. According to the literature and the current status of our own results, the formation temperature of the V8SiB4 phase can be assumed to be in the range between 1400 °C and 1600 °C from the V5SiB2 phase. This appears to be a transformation from the V5SiB2 phase. Furthermore, the mechanical properties of the Vss−V3Si−V5SiB2 and the Vss−V5SiB2 eutectic alloys were investigated in the temperature range from 25 °C to 1000 °C. The primary objective of this follow-up proposal is to investigate the phase stability of the new V8SiB4 phase depending on the temperature and the alloy composition. A monolithic V8SiB4 phase will be produced using powder metallurgy (PM), i.e. mechanical alloying and sintering (FAST). The postulated solid-solid transformation behavior will be investigated via DSC measurements in combination with purposefully selected heat treatment experiments.To determine the solubility range of the V8SiB4 phase, 2-3 variants with slight variations in the stoichiometry of the new phase will be prepared and investigated. In addition, EDX and/or WDX measurements will be performed to narrow down the solubility range. Subsequently, the V-Si-B database (FactSage) created in the previous project period will be expanded to include the latest findings. As a second focus of the proposed project, the mechanical behavior of the V8SiB4 phase will be investigated on the micro- and macroscales. V8SiB4 and V5SiB2 phases will be studied by nanoindentation and electron microscopy to characterize the deformation mechanisms and mechanical properties as a function of crystal orientation. On the macroscale, the compressive yield strength and the creep resistance of polycrystalline V8SiB4 and V5SiB2 phases will be tested at 900 °C and 1000 °C. The determined mechanical parameters of the two intermetallic phases will then be applied in a model to describe the deformation parameters of an alloy from the first funding period.