Influence of mechanical surface treatments on the high cycle fatigue performance of TIMETAL 54M

TIMETAL 54M (in the following Ti-54M) is a newly developed (α + β) titanium alloy with nominal composition Ti–5Al–4V–0.6Mo–0.4Fe. The alloy can provide a cost benefit over Ti–6Al–4V due to improved machinability and formability. These attractive properties might be a driving force for replacing Ti–6Al–4V in many aircraft as well as biomedical applications. Since HCF performance is one of the most important requirements for these applications, it is essential to improve this property by microstructural optimization and by mechanical surface treatments such as shot peening or ball burnishing. The latter improvement is mainly the result of induced near-surface severe plastic deformation which results in work-hardening and the generation of compressive residual stresses that retard fatigue crack propagation. The main aim of the present study was to investigate the potential fatigue life improvements in Ti-54M due to shot peening and ball-burnishing. The process-induced residual stresses and stress–depth profiles were determined by energy-dispersive X-ray diffraction (ED) of synchrotron radiation with the beam energy of 10–80 keV. Results on Ti-54M and Ti–6Al–4V will be compared and correlated with the mean stress and environmental sensitivities of the fatigue strengths in the microstructures.