Hydrogen embrittlement properties of 7075 and 6061 aluminum alloys in humid air

Abstract

For 6061-T6 and 7075-T6 aluminum alloys as candidate liner materials for high-pressure hydrogen container, SSRT (slow strain-rate technique) tests in humid air with 90% relative humidity were carried out to evaluate the susceptibility to hydrogen embrittlement (HE) and to reveal the process of HEAC (hydrogen-environment -assisted cracking). 7075-T6 showed a significant susceptibility to HE, resulting in intergranular cracking, while in contrast, 6061-T6 exhibited an excellent resistance required as liner materials. HEAC of 7075-T6 is confirmed to progress as follows; at the first stage micro-cracks originate at inclusions of Al–Fe–(Cu) phase on the specimen surface and then advance to intergranular cracking. 6061-T6 would not give rise to micro-cracks because of less localization of slip deformation enhanced by hydrogen effects, mainly due to the precipitation microstructure.