Fatigue crack growth behavior of X2095 Al-Li alloy

Microstructures and micro-textures of X2095 Al-Li alloy in as-received/superplastic state were characterized by means of SEM/BDS, X-ray diffraction and orientation imaging microscopy (OIM). It was observed that the microstructure of the alloy was typical of a particulate-reinforced composite material, consisting of aluminum matrix and homogeneously distributed T-B(Al7Cu4Li) particles with a volume fraction of about 10%. Brass-type texture was the dominant texture component. Both constant amplitude and near-threshold fatigue crack growth rates of the alloy in the L-T and T-L orientations were determined at different stress ratios. Particular attention was paid to the role of the T-B phase in the fatigue crack growth. When a fatigue crack approached a T-B particle, the crack basically meandered to avoid the particle. The T-B particles thus provided a strong resistance to the propagation of fatigue crack by promoting crack deflection and the related crack closure effects. The fatigue crack propagation behavior has been explained by the microstructural features, micro-textures, cracking characteristics and crack closure effects. (C) 1999 Elsevier Science Ltd. All rights reserved.