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

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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