OS1512 カソード電位制御下におけるAZ61マグネシウム合金の疲労き裂進展挙動

Abstract

It is known that the fatigue crack propagation (FCP) behavior of magnesium (Mg) alloy is sensitive to the environment, because the corrosion resistance of Mg alloy is rather poor. In the previous works, the authors had conducted FCP tests using some Mg alloys under controlled humidity, and concluded that the FCP rates could be accelerated by the humidity in air. In addition, the hydrogen microprint method had revealed that the hydrogen atoms diffused along the crack-wake. Thus it was expected that the acceleration mechanism of FCP rates could be attributed to both anodic dissolution and hydrogen embrittlement at the crack tip. However, it is difficult to estimate the both effects separately, and the influence of hydrogen on FCP behavior is unclear. In the present study, FCP tests on Mg alloy, AZ61, were performed in 3% NaCl solution. The cathodic potential was controlled to achieve the hydrogen charged condition without anodic dissolution to figure out the effect of hydrogen on FCP. The cathodic potential was set to -3.0V, which corresponded to the immunity region without corrosion reaction based on the Pourbaix diagram of Mg. The FCP rates accelerated under hydrogen charged condition compared to those in dry air.