Volume 6, Issue 2 (March 1978)
Comparison of Stress Corrosion Cracking Properties of Several Aircraft Structural Alloys
Sustained load subcritical flaw growth characteristics of five alloys of interest to aircraft designers were investigated. The aluminum alloy (2024-T851) and steel alloy (18Ni-maraging) were studied in 3.5% sodium chloride solution and high humidity air environments while two of the titanium alloys, Ti-6Al-4V (recrystallized annealed) and Ti-6A1-6V-2Sn (solution-treated and overaged), were also investigated in these environments plus sump tank water. The Ti-6Al-4V (beta) alloy was tested in 3.5% sodium chloride solution. Wide differences between the alloys were noted not only in their cracking rates but also in their responses to similar loads and environments. Specimen thickness was found to have an important effect on stress corrosion susceptibility of the titanium alloys. Many coupons of specific titanium alloys had significant subsurface crack growth without visible surface growth. For these alloys, no precise threshold for stress corrosion cracking could be defined.