Relationship between hydrogen embrittlement and second-phase particles in a 7075 aluminum alloy

With respect to hydrogen embrittlement process in a 7075 alloy in humid air, it has been claimed that cracks at second-phase particles result in intergranular cracking. In this study, slow strain rate tensile tests in two environments and microscopic surface observation were carried out to investigate the hydrogen embrittlement process of a 7075 alloy. It was confirmed that elongation in humid air was smaller than in dry nitrogen gas due to hydrogen embrittlement. In both environments, cracks were observed in second-phase particles on the specimen surface during tensile deformation. The amount of cracks in second-phase particles was not larger in humid air than in dry nitrogen gas. Moreover, they did not grow into the aluminum matrix in both environments. Some intergranular cracks were observed on the specimen surface without a cracking of second-phase particles in humid air. Therefore, hydrogen embrittlement in a 7075 alloy based on intergranular cracking in humid air is not caused by a cracking of second-phase particles on the specimen surface.