In-situ Studies of Deformation Behavior and Damage Evolution in High Temperature Titanium Alloy IMI 834

Kurzfassung

The low-cycle fatigue behavior of near-α titanium alloy IMI 834 was studied in-situ at a temperature of 400 °C. The in-situ fatigue tests were conducted in an environmental scanning electron microscope under both high vacuum and 20 Torr of water vapor. In both environments, slip bands were observed to originate within the primary α grains rapidly. Slip bands were more numerous and more uniformly distributed when tests were conducted in vacuum. Crack nucleation also occurred along the slip bands but cracks appeared distinctly earlier in water vapor. The humid atmosphere presumably both eased crack initiation and accelerated crack growth due to environmental attack. Both mechanisms provide a rational for the pronounced decrease in cyclic life observed in water vapor compared to cycling in vacuum.