The microstructure and environment influence on fatigue crack growth in 7049 aluminum alloy at different load ratios

The role of microstructure and environmental influence on fatigue crack has been investigated on a high strength 7049 aluminium alloy, artificially aged to underaged (UA) and overaged (OA) microstructures with approximately the same yield strength properties, but differing in the mode of slip deformation. The UA alloy deforms by planar slip while the OA alloy by wavy slip. Crack growth measurements were performed at constant load ratios, between 0.8 and −1, in ambient air and vacuum. The influence of load ratio is discussed in terms of slip deformation mechanisms, microstructure, and the influence of environment using the two intrinsic parameters, ΔK and Kmax.