Effects of temperature on the fatigue crack growth of an Al-Li 8090 alloy with δ’ microstructure

Abstract

Recently, it has been found that Al-Li alloys display enhanced strength, ductility, and toughness at cryogenic temperatures, with possible mechanisms for this enhancement being the increased strain hardening capacity, the immobilization of low melting-point impurities segregated at the grain boundaries, the decrease in stacking fault energy promoting the deformation by twinning, and the intensified delamination at cryogenic temperatures. A substantially improved high cycle fatigue strength at cryogenic temperatures has also been reported for some Al-Li alloys. However, there have been very limited data sources reported for the fatigue crack growth (FCG) behavior of Al-Li alloys at Cryogenic temperatures, One of which shows that the FCG rate of a 2090 alloy decreases with decreasing temperature to 77 K. The underlying mechanism for this increased resistance to FCG induced by the cryogenic temperature environment has not been clarified. Therefore, the present investigation is aimed to examine the FCG behavior of an Al-Li 8090 alloy at both room (298 K) and cryogenic (77 K) temperatures and to understand its mechanisms.