Very High Cycle Fatigue and Damage Behavior of Ti6Al4V

Abstract:

High frequency fatigue tests were carried out with a 20 kHz ultrasonic testing facility to investigate the cyclic deformation behavior of Ti6Al4V in the Very High Cycle Fatigue (VHCF) regime in detail. The S,N_f -curve at the stress ratio R = -1 shows a significant decrease of the stress amplitude and a change from surface to subsurface failures in the VHCF regime for more than 10⁷ cycles. Microscopic investigations of the distribution of the α-and β-phase of Ti6Al4V indicate that inhomogeneities in the phase distribution are reasons for the internal crack initiation. Scanning electron microscopy as well as light microscopy were used to investigate the internal crack initiation phenomenon in the VHCF-regime. Beside the primary fatigue crack additional defects like micro cracks and crack clusters were observed in the fatigued specimens. SEM-investigations of specimens which were loaded up to 10¹⁰ cycles without failure show irreversible microstructural changes inside the specimens. Two step tests were performed to evaluate the influence of internal fatigue induced defects observed in specimens which did not fail within 10¹⁰ cycles.

• Periodical: Key Engineering Materials (Volume 664)
• Pages: 71-80
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.664.71
• Online since: September 2015
• Authors: Stefan Heinz, Dietmar Eifler*
• Keywords: Cyclic Deformation Behavior, Damage Mechanisms, Ti6Al4V, VHCF

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