Effect of environmental relative humidity on hydrogen-induced mechanical degradation in an Al–Zn–Mg–Cu alloy

Abstract The influence of relative humidity (RH) on mechanical properties of a 7075 alloy, cold finished aluminum wrought product, was studied by slow strain rate technique in atmospheres with various RHs. Hydrogen was introduced into specimens from the testing environment during deformation and then thermal desorption spectrometry was utilized to determine the content of absorbed hydrogen. By increasing the RH in slow strain rate tensile tests, the ultimate tensile strength remained unchanged, the content of hydrogen increased, and the total tensile elongation reduced, revealing an increase in the hydrogen embrittlement sensitivity (HES). In RHs below 40%, the HES was insignificant. However, by increasing the RH, a sharp increase in HES was observed due to the formation of secondary cracks. The results firstly showed that even a normal humidity (40–60%) of the testing environment at room temperature can lead to a significant HES in a wrought aluminum alloy.