Evaluation of Susceptibility to Hydrogen Embrittlement of 7075 Aluminum Alloy by Hydrogen Addition Using Flax-Treatment Method

Abstract

It is more difficult with aluminum alloys to investigate the effect of hydrogen on their mechanical properties than with steels because of their stable and protective oxide films, which act as a strong barrier for hydrogen penetration. In this study, after the flux-treatment, 7075-T6 alloy was subjected to thermal desorption spectroscopic (TDS) analysis and tensile test using the slow strain rate technique (SSRT) to establish a procedure for adding hydrogen to aluminum alloys and clarify the influence of hydrogen on their environmental embrittlement. The fluxtreatment consisted of applying a flux-solution for soldering on specimen surfaces and vaporizing water of the solution. These flux-treated specimens were exposed in a desiccator for various periods of time and then the solidified-flux and corrosion products were removed from the specimen surfaces before the TDS analysis and the tensile test. The experimental results revealed that hydrogen was absorbed into the alloy by the flux-treatment and the hydrogen content had a tendency to increase with increasing exposure time. Additionally, the fracture strain of tensile specimen decreased with exposure time, resulting in more severe embrittlement. Consequently, this flux-treatment method was considered to be an appropriate procedure for adding hydrogen to aluminum alloys and for evaluating their susceptibility to hydrogen embrittlement when combined with SSRT.

Chemical reactions in cracks of aluminum crystals: Generation of hydrogen from water

“…2 the peaks above 350 1C are possibly from hydrogen existing at crystalline defects like grain boundaries. Such a fact is suggested by experiments in our group [6]. The number of H atoms in Al n particles is calculated from the number of desorbed H 2 molecules shown in Fig.…”

“…It might be very difficult for us to observe the inside of micro-cracks in metal crystals especially in water. However, we can have somewhat concrete images of cracks in Al crystals from macroscopic observations [3,6]. Crack formation starts from grain boundaries on surfaces of Al crystals due to corrosions by H 2 O, and the micro-cracks grow into the interior of Al crystals.…”

Study of Hydrogen-Induced Plastic Damage Response of 7085-T7651 High-Strength Aluminum Alloy

“…Swapnar et al [13] showed that, at intermediate strain rates, the film interfered and reduced hydrogen entry at intermediate strain rates, while hydrogen embrittlement was significant at the slowest strain rates. Komazaki [14] revealed that hydrogen was absorbed into the alloy by flux treatment and hydrogen content tended to increase with increasing exposure time. However, hydrogen is difficult to detect, and has strong diffusivity in materials.…”