Abstract
To improve tank safety for fuel cell vehicles and promote the application of aluminum alloys to high-compression hydrogen gas tank liners, it is important to clarify the fatigue properties of aluminum alloys as affected by atmospheric hydrogen. In this study, the effect of elastic fatigue deformation on hydrogen diffusion for 7075 aluminum alloy was investigated by means of hydrogen microprint technique. The fatigue test was carried out under the various parameters for frequency (10 Hz, 1 Hz, or 0.1 Hz) and applied maximum stress (80%, 60%, or 40% of proof stress (525 MPa for 7075-T6 alloy)). In all fatigue tests, accumulated hydrogen was mainly observed within second phase inclusion such as Al_7Cu_2Fe. This shows that Al_7Cu_2Fe acts as hydrogen diffusion path during elastic fatigue deformation. The amount of hydrogen accumulation increased with decreasing fatigue test frequency, which shows that the hydrogen diffusion is influenced by deformation time. Hydrogen accumulation also increased with increasing maximum stress, which indicates that hydrogen evolution during elastic fatigue deformation is controlled by stress-induced diffusion.
