Stress corrosion cracking (SCC) tests were conducted in 1N AlCl3 solution on 7075 aluminum in three tempers: T6, T73, and an underaged temper (UT) approximately equal in strength to T73. Tests were conducted both in mode I (tension) and in mode III (torsion). Increasing the degree of temper (UT → T6 →T73) reduced susceptibility to SCC in modes I and III; UT and T6 were much less different in this ranking than were T6 and T73. The mechanical and fractographic results were interpreted to suggest that the predominant mechanisms of SCC were hydrogen embrittlement in mode I and anodic dissolution in mode III. However, a corrosion (non-SCC) component of crack advance was also present in T73 tests, indicating that accelerated laboratory SCC tests using AlCl3 could be misleading.

Subject
Scanning electron microscopy, Test methods, Intergranular stress corrosion cracking, Secondary cracks, Stress intensity, Aluminum, Stress, Corrosion attacks, Mechanical failure, Aluminum alloys, Fracture, Stress corrosion cracking, Aging
National Association of Corrosion Engineers
1985
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