Mechanisms of fatigue crack propagation in titanium alloys at elevated temperature: environmental influence

摘要

This paper deals with a study of fatigue crack propagation in a Titanium alloy type 6246 forged at 950°C and treated to display a Widmanstatten microstructure. Tests were performed at 500°C under sinusoidal and dwell waveforms at various frequencies and in different environmental conditions including high vacuum, air, and argon with controlled partial pressure of water vapour. Closure correction was systematically done. Enhanced propagation rates observed in moist environments as compared to high vacuum are associated to corrosion-fatigue and/or creep-fatigue mechanisms induced by water vapour. The respective roles of oxygen and water vapour are discussed.