The hierarchy of microstructure parameters affecting the tensile ductility in centrifugally cast and forged Ti-834 alloy during high temperature exposure in air

Ductility regression is the main concern in using Ti-834 titanium alloy at temperatures above 500 °C for aerospace applications. The reduction of ductility in titanium alloys at high temperatures is strongly correlated to the exposure time. In the current study the effect of prolonged exposure at 500 °C on the tensile ductility of two differently processed Ti-834 alloys was investigated. In order to simulate actual … Continue reading The hierarchy of microstructure parameters affecting the tensile ductility in centrifugally cast and forged Ti-834 alloy during high temperature exposure in air

A new statistical framework for the determination of safe creep life using the theta projection technique

In this article a new estimation framework is put forward for the well-known theta projection technique which enables, for the first time, levels of confidence to be associated with the creep property predictions made using this technique. The predictions made from the resulting model are in the form of distributions, which is a substantial advance on existing life assessment methodologies used in high-temperature applications such … Continue reading A new statistical framework for the determination of safe creep life using the theta projection technique

Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions

Investigations of Timetal 834 crept specimens showed that a uniform alpha-case layer was developed at the surfaces of all specimens tested in air at 823 K to 923 K (550 °C to 650 °C). The formation of this alpha-case was a result of the inward diffusion of oxygen, which is an alpha stabilizer, and other elements promoting the transformation of the beta matrix into an alpha phase and, thus, … Continue reading Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions

Insights into microstructural interfaces in aerospace alloys characterised by atom probe tomography

Atom probe tomography (APT) is becoming increasingly applied to understand the relationship between the structure and composition of new alloys at the micro- and nanoscale and their physical properties. Here, we use APT datasets from two modern aerospace alloys to highlight the detailed information available from APT analysis, along with potential pitfalls that can affect data interpretation. The interface between two phases in a Ti–6Al–4V … Continue reading Insights into microstructural interfaces in aerospace alloys characterised by atom probe tomography

Domestic object damage and fatigue behaviour of an advanced gamma TiAl alloy

Laboratory simulated domestic object damage (DOD) was imposed on aerofoil style specimens manufactured from a latest generation gamma titanium aluminide. The form of the impact sites was characterised in detail before assessment under fatigue loading at room temperature and 650°C. A reduction in fatigue strength due to the presence of DOD was shown to be sensitive to the projectile impact energy but independent of test … Continue reading Domestic object damage and fatigue behaviour of an advanced gamma TiAl alloy

Titanium alloy developments for aeroengine fan systems

Recent research relating to two α+β processed titanium alloys, designed for specific employment in aeroengine fan disc and aerofoil components, is described. Timetal 575 (Ti575) and Timetal 639 (Ti639) are both novel compositions that provide relatively high strength compared to Ti–6Al–4V. Static and cyclic behaviour of the two developmental alloys were evaluated at room temperature. A dwell fatigue assessment of Ti575 is reported, while the … Continue reading Titanium alloy developments for aeroengine fan systems

Experimental and crystal plasticity studies of deformation and crack nucleation in a titanium alloy

This paper presents recent developments in crystal plasticity modelling to incorporate a non-local crack nucleation criterion and the comparison of experimental observations and model predictions for deformation and crack nucleation in a near-alpha titanium (Ti) alloy polycrystal. The model polycrystal was established so as to have grain morphology and crystallography nominally identical to that in the experiment, enabling direct interpretation and comparison of the results. … Continue reading Experimental and crystal plasticity studies of deformation and crack nucleation in a titanium alloy