Effect of strain rate on environmental hydrogen embrittlement susceptibility of a severely cold-rolled Al-Cu alloy

This study investigated the effect of strain rate ranging between 1.7 x 10(-4) and 1.7 x 10(-8) s(-1) on environmental hydrogen embrittlement behavior in a severely cold-rolled Al-Cu alloy. Elongations of the specimens tensile-tested in humid air (HA) decreased significantly compared with the specimens tensile-tested in dry nitrogen gas at strain rates of 1.7 x 10(-5), 1.7 x 10(-6) and 1.7 x 10(-7) s(-1). With decreasing the strain rate, the hydrogen embrittlement sensitivity (HES) index of the alloy first increased and then decreased with the maximum occurring at 1.7 x 10(-6) s(-1), exhibited a largest amount of desorbed hydrogen. The characteristics of the fracture behavior of the specimens tensile-tested in HA also changed with the strain rate. Thermal desorption spectroscopy results revealed that the amount of trapped hydrogen at dislocations and/or second phase particles has a correlation with HES index.