Stress corrosion cracking of 7xxx aluminum alloys in high humidity environments

The release of Safety Information Bulletin SIB 2018-04 by the European Aviation Safety Agency has prompted significant interest within the aerospace industry regarding the cracking behavior of 7000-series aluminum alloys in humid environments. The bulletin contains a description of the associated fracture surfaces, and the revised bulletin (SIB 2018-04R1) describes a test procedure in humid air for determining potential material susceptibility.

This presentation will demonstrate the consistency of the EASA bulletin’s description of the observed fracture surfaces with the scientific literature on the topic of Stress Corrosion Cracking. The performance of legacy and advanced 7000-series products in existing industry standard testing methods, such as ASTM G44/G47, will be compared to tests in humid air. The propagation mechanisms relevant to both types of testing and to in-service failures reported in the literature will be discussed.