Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Naval Air The effects of environment concentration and strain rate on the stress corrosion cracking (SCC) behavior of 5083-H131 and 7075-T6 aluminum alloys were studied, conducting electrochemical measurement and slow strain rate test. The employed environments were pH 7.3 aqueous solutions of 0 to 20% NaCl, and the applied strain rate ranged from 10 -8 s -1 to 10 -4 s -1 . A comparative test was also carried out in air. After the tests, the fracture surface morphology was examined by scanning electron microscopy, and the microstructure in the vicinity of the fracture by light microscopy to clarify the SCC mode. The results indicated: 1. The SCC susceptibility is a little below 0.5% NaCl but it is raised noticeably with increasing NaCl concentration above 0.5% NaCl. 2. Compared to 7075-T6 aluminum alloy, 5083-H131 aluminum alloy has inferior mechanical property and it is highly susceptible to SCC. 3. The corrosion potential is lower and the corrosion rate is greater for higher NaCl concentration. 4. The SCC susceptibility increases with decreasing strain rate. 4. The SCC mode is crack initiation at the junctions of grain boundaries with specimen surface, and crack propagation along grain boundaries into the specimen, attributed to hydrogen embrittlement and anodic dissolution. ii SUMMARY The effects of environment concentration and strain rate on the stress corrosion cracking (SCC) behavior of 5083-H131 and 7075-T6 aluminum alloys were studied, conducting electrochemical measurement and slow strain rate test. The employed environments were pH 7.3 aqueous solutions of 0 to 20% NaCl, and the applied strain rate ranged from 10 -8 s -1 to 10 -4 s -1 . A comparative test was also carried out in air. After the tests, the fracture surface morphology was examined by scanning electron microscopy, and the microstructure in the vicinity of the fracture by light microscopy to clarify the SCC mode. The results indicated: 1. The SCC susceptibility is a little below 0.5% NaCl but it is raised noticeably with increasing NaCl concentration above 0.5% NaCl. 2. Compared to 7075-T6 aluminum alloy, 5083-H131 aluminum alloy has inferior mechanical property and it is highly susceptible to SCC. 3. The corrosion potential is lower and the corrosion rate is greater for higher NaCl concentration. 4. The SCC susceptibility increases with decreasing strain rate. 4. The SCC mode is crack initiation at the junctions of grain boundaries with specimen surface, and crack propagation along grain boundaries into the specimen, attributed to hydrogen embrittlement and anodi...