低歪速度法によるＡＺ３１Ｂマグネシウム合金の応力腐食割れ感受性

概要

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Due to advantages such as high strength-to-weight ratios, specific castability and recycling efficiency, magnesium alloys are used in a wide variety of industrial applications. Stress corrosion cracking (SCC) tests of AZ31B magnesium alloy in distilled water and 2∼8wt% sodium chloride solutions at 298K were performed with slow strain-rate technique. In a distilled water, the SCC of the magnesium alloy occurs surely and its susceptibility increases with a decrease of strain-rate. This magnesium alloy in sodium chloride solutions is very susceptible to the SCC under open circuit condition, regardless of the strain-rate and solution concentration. The SCC in 4wt% sodium chloride solution under potential-controlled condition occurs near the corrosion potential, which lies to the potential range of hydrogen evolution. Furthermore, the fracture surface is characterized by transgranular quasi-cleavage appearance. The evidence introduced here supports a hydrogen embrittlement for the SCC of AZ31B magnesium alloy in sodium chloride solution, including an anodic dissolution mechanism by chloride ion.