INVESTIGATION OF THE STRESS CORROSION CRACKING AND CORROSION FATIGUE RESISTANCE OF CONVENTIONAL AND NANOSTRUCTURED Al-Mg ALLOYS

摘要

The corrosion behavior of nanocrystalline Al-Mg based alloys was investigated and compared to their conventional counterpart 5083(H111). Specifically, the stress corrosion cracking (SCC) behavior and corrosion fatigue (CF) were studied. The pitting densities, average pit depths and crack initiation time were measured under different loading conditions after alternate immersion in artificial seawater after time intervals of 2 weeks, 1 month, 2 months and 6 months. Scanning Electron Microscopy (SEM) was used to analyze the fracture surface of the failed specimen after removal at selected intervals and tensile testing. S/N curves were generated for the nanocrystalline Al-Mg based alloy and the conventional counterpart 5083 in air and seawater. A range of microstructural and fundamental electrochemical experiments were aimed at identifying the role that the grain boundaries play in altering the localized corrosion mechanisms of the alloys. The results of this investigation will provide the necessary information regarding the role that ultra-fine microstructures play in their degradation in marine environments.