Assessment of new fatigue capable titanium alloys for aerospace applications

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Titanium alloys are used in high performance rotating components for both large and small/medium civil gas turbines. For applications such as fan blades and fan discs, titanium alloys with enhanced strength and fatigue performance are required. Rolls-Royce currently utilises mainly Ti-6Al-4V for applications under 350C with new titanium alloys currently under development. As part of the ATI funded BETA program a number of commercially developed and R-R IP alloys are being considered. These alloys are RR11, S23, Ti542, Ti407, Ti412 and Titan 27.Latest developments on jet engines have raised the need for an alternative to Ti-6Al-4V with improved Range-mean fatigue performance, damage tolerance and cold dwell fatigue insensitivity while having good weldability to other titanium alloys and whose properties must be maintained after post welding heat treatment.Ti407 and Ti412 are known as lean aluminium alloys as they have much lower aluminium contents than common titanium alloys such as Ti-6Al-4V. They have been developed to enhance ductility at failure and hence energy absorption capability. Ti542 has been developed by Timet to be an alternative to Ti64 that is less sensitive to cold dwell. S23 has been developed via powder metallurgy route as a high strength titanium alloy may show enhanced fatigue performance. Finally, Titan27 has been developed as an improved Ti64 with excellent cold and hot workability.The primary purpose of this investigation is to develop fundamental understanding of how the down selected alloys respond to mechanical loading.It is envisaged that work would be carried out on the processing and optimization on the down selected materials to investigate the effect of chemistry variation using small scale melts and processing routes on the mechanical properties and its scalability to production size components.During the programme, the student will develop core skills in advanced microscopy, such as microstructural and texture characterisation, fundamental titanium metallurgy and thermomechanical processing. The student will develop an insight into the development path of alloys for usage in the aerospace sector and work closely with engineers at Rolls-Royce.