文摘
High-strength aluminum alloy AA7075 forgings are widely used in various control system components of liquid engines of satellite launch vehicles. In one such application, a forged component was found to crack under storage. Multiple cracks were noticed on the surface of the component. Fractographic features indicated intergranular mode of failure. Optical microscopic examination revealed dendritic coring in the material and crack propagation to be along the grain boundaries. Anodic dissolution of grain boundaries was also noticed. Based on detailed metallurgical investigations, it was concluded that the failure was due to ‘stress corrosion cracking.’