Surface Condition Effect on the Fatigue Behavior of Aluminum Lithium Alloys

摘要

Production of Al-Li 2090-T3 alloy by powder metallurgy results in a material witha surface that contains micro and macro defects. In addition, scratches could be introduced to the surface during assembling and/or processing with a drastic decrease in a fatigue strength. The effects of scratch are so severe that a smooth sample with a scratch of 200 micrometers will have a fatigue life as a notched sample with KT = 3, a reduction in fatigue life of about three orders of magnitude. In order to recover the loss, shot peening, polishing, anodizing and some of the combined effects of these techniques have been studied. Depending on the applied stress, the fatigue strength of scratched samples, up to certain depth, can be partially recovered and some of these treatments have accumulative results on improving the fatigue life. The results are discussed in relation to the potential effects of defects on the nucleation of microcracks and their propagation.