Visualization of hydrogen during fatigue fracture in an Al-Mg-Si alloy

Abstract

Hydrogen accumulation during fatigue of a bake-hardened Al-Mg-Si alloy was investigated by means of hydrogen microprint technique. As a result of S-N curve relation as a function of testing frequency, effect of environmental hydrogen on fatigue properties was not clearly identified. Based on the low cycle fatigue test with 60MPa stress amplitude, it was revealed that hydrogen was accumulated on slip bands and that distribution of hydrogen emission was changed in the crack propagation direction. Hydrogen was preferentially accumulated at the coarse slip bands near the fatigue crack where the separation of slip planes was observed in the fracture surface. On the other hand, hydrogen was observed on the slip lines arranged like steps where the fatigue striations were formed in the fracture surface. At near the final fracture area where the fine slip bands were formed on specimen surface, hydrogen was arranged on each slip bands formed by multiple slips.