Effect of aging microstructure on hydrogen embrittlement sensitivity in an Al-Mg-Si alloy

In recent years, the fuel cell vehicle that uses hydrogen as clean energy has been developed among automobile companies. To store high compressed hydrogen gas in the fuel cell vehicle, a special tank is needed and Al-Mg-Si base alloys have been regarded as one of the candidate materials for the tank liner. However, little is know about the effect of atmospheric hydrogen on the mechanical properties of the Al-Mg-Si alloy. In this study, effect of aging microstructure on hydrogen embrittlement (HE) sensitivity of the Al-Mg-Si alloy was investigated by means of the tensile testing machine equipped with quadruple mass spectrometer in an ultrahgh vacuum chamber, which was originally developed by our group. It is proved that the elongation decreases when the slow strain rate testing (SSRT) is carried out in humid air. The amount of hydrogen evolution at the moment of fracture is clearly decreased particularly in the OA specimen. The hydrogen desorption amount from the OA specimen is smaller than that from the PA specimen after the predeformation by SSRT. As the aging proceeds, the composition of the grain boundary precipitates is changed. It is assumed the PA condition has higher capability to trap hydrogen than the OA condition in the Al-Mg-Si alloy.