Effect of extrusion aspect ratio and test temperatures on fatigue crack growth behavior of a 2099-T83 Al–Li alloy

Fatigue crack growth (FCG) behavior of an integrally stiffened panel (ISP) of the 2099-T83 Al–Li alloy was investigated both at ambient (23 °C) and low (−30 °C) temperatures. FCG rates have been found to correlate with the local extrusion aspect ratio (AR), as a result of the combined effects of both the grain structure and the crystallographic texture, regardless of the test temperature. The resistance to FCG increased with decreasing temperature, this effect being attributed to a decrease in humidity content in the studied temperature range. Fractographic examinations indicate that the changes in FCG resistance with temperature are associated with a change in the fracture surface roughness and crack path tortuosity, which likely control the migration of water vapor to the crack tip.