Influence of solution heating rate on grain structures and fatigue crack propagation behaviors of an aviation Al-Li alloy sheet

Abstract

In this study, the effects of grain structure on the fatigue crack propagation (FCP) behaviors in the aviation Al-Li alloy sheets prepared by varying solution heating rates are discussed systematically. The results reveal that both the intensity of Goss texture and grain dimensions are improved with the decreased solution heating rates. Upon an identical stress intensity factor range (ΔK), the increased Goss texture of the sample with a solution heating rate of 2 ℃/min (2HR) promotes crack deflection, causing a decrease in FCP rates compared to that of the sample with a solution heating rate of about 100 ℃/min (FHR). The dislocations clustered near grain boundaries are more significant with increasing grain size during cyclic loading, which intensifies the strain localization. The accumulation of dislocations increases the possibility of micro-voids formation and creates the conditions for crack deflection, which results in a decrease in FCP rate. Besides, based on the calculation of the reversible plastic zone (RPZ) size, the initial ΔK entering the rapid propagation region increases with decreasing solution heating rates and exhibits a strong linear relationship with grain size.