The Influence of Combined Oxidation and Fatigue on the Endurance of Titanium Alloys

高性能钛合金正越来越多地应用于需要高温的先进机身中（例如，靠近发动机的地方）。虽然钛合金在低温下抗氧化，但在350℃以上的温度下，钛合金容易因氧化和氧气扩散到其表面而降解，在极端情况下，这可能会改变表面下的微观结构并导致脆化。目前，人们对氧化、溶解氧与疲劳裂纹萌生和扩展之间的相互作用知之甚少，这使得预测在役部件的耐久性变得困难。因此，对于钛机身合金，更清晰、更深入地了解高温疲劳和氧化环境之间的协同作用是很重要的。本项目将在受控条件下进行疲劳试验，研究氧化对疲劳寿命的影响，从短裂纹的萌生到长裂纹的扩展速度。这将包括研究动态变形对氧扩散和裂纹尖端损伤行为的影响，作为温度、停留时间和大气的函数。该研究还将采用先进的显微镜方法、x射线断层扫描3D成像和微观力学分析，以高分辨率研究氧化-裂纹相互作用，最终目标是能够更可靠地预测部件寿命。该项目将有助于研究旨在支持更质量高效的先进机身部件设计，并将通过空中客车机身研发部门的先进金属研究计划（AMRP）进行监督

High performance titanium alloys are being increasingly used in advanced airframes where elevated temperatures are experienced (e.g. in close proximity to engines). While oxidation resistant at low temperatures, at temperatures above 350C titanium alloys are prone to degradation from oxidation and diffusion of oxygen into their surfaces, which in extreme cases can change the subsurface microstructure and cause embrittlement. The interactions between oxidation, dissolved oxygen, and fatigue crack initiation and propagation, are currently poorly understood, which makes predicting the endurance of components in-service difficult. With titanium airframe alloys it is therefore important to obtain a clearer in-depth understanding of the synergistic interactions between elevated temperature fatigue and an oxidising environment.This project will use fatigue tests under controlled conditions to study the effects of oxidation on fatigue life, from the initiation of short cracks to the growth rate of long cracks. This will involve studying the effects of dynamic deformation on oxygen diffusion and the crack tip damage behaviour, as a function of temperature, dwell time and the atmosphere. The research will also involve employing advanced microscopy methods, 3D imaging by x-ray tomography, and micromechanical analysis, to study the oxidation-crack interactions at a high resolution, with the ultimate goal of being able to more reliably predict component life. The project will contribute to research aimed at supporting the more mass-efficient design of advanced airframe components and will be supervised through the Advanced Metallic Research Programme (AMRP) within Airbus Airframe R&T