TY - JOUR
T1 - Damage micromechanisms of stress corrosion cracking in Al-Mg alloy with high magnesium content
AU - Hirayama, Kyosuke
AU - Toda, Hiroyuki
AU - Fu, Dongsheng
AU - Masunaga, Ryohei
AU - Su, Hang
AU - Shimizu, Kazuyuki
AU - Takeuchi, Akihisa
AU - Uesugi, Masayuki
N1 - Funding Information:
The synchrotron experiments were performed with the approval of JASRI, through proposal numbers 2019A0076, 2018B0076, 2018A0076, 2017B0076, and 2017A0076. One of the authors (HT) is also grateful for the support of the Grant-in-aid for Scientific Research from JSPS, Subject No. 17H01328, and the Light Metal Educational Foundation.
Publisher Copyright:
© 2021 The Authors
PY - 2021/5/15
Y1 - 2021/5/15
N2 - Al-10Mg alloys, which are highly susceptible to SCC, were prepared with various β precipitate morphologies. Interrupted in-situ tensile tests were conducted under synchrotron X-ray radiation, employing a recently developed X-ray microtomography technique that combines high-energy, applicability to metallic materials, and ultra-high resolution. Preferential dissolution of the β phase along grain boundaries, and incidental intergranular and transgranular fracture, were observed in 3D. A drastic decrease in SCC resistance was measured after hydrogen charging. The additional effect of external hydrogen absorbed from an aqueous solution during loading was also revealed, by directly measuring crack-tip plasticity. The aquatic environment, one of the most extreme conditions for hydrogen uptake, caused continuous crack-tip corrosion. Catastrophic failure was observed when an alloy had both a relatively high areal grain boundary coverage by film-like β phase, and a reticulately interconnected plate-like β phase in the grain interior. Hydrogen bubble formation was also observed, in relation to the progress of crack-tip corrosion. The main corrosion product was identified as Al(OH)3, based on its linear absorption coefficient. The respective amounts of corrosion products and hydrogen gas in the gas bubbles, and the pH value of the aqueous solution, were accurately measured during in-situ tensile testing, enabling estimation of the local elevation of hydrogen content in the crack-tip vicinity. Finally, a quantitative criterion for the occurrence of hydrogen embrittlement in inter-β ligaments is discussed, together with the applicability of the findings to the prevention of SCC.
AB - Al-10Mg alloys, which are highly susceptible to SCC, were prepared with various β precipitate morphologies. Interrupted in-situ tensile tests were conducted under synchrotron X-ray radiation, employing a recently developed X-ray microtomography technique that combines high-energy, applicability to metallic materials, and ultra-high resolution. Preferential dissolution of the β phase along grain boundaries, and incidental intergranular and transgranular fracture, were observed in 3D. A drastic decrease in SCC resistance was measured after hydrogen charging. The additional effect of external hydrogen absorbed from an aqueous solution during loading was also revealed, by directly measuring crack-tip plasticity. The aquatic environment, one of the most extreme conditions for hydrogen uptake, caused continuous crack-tip corrosion. Catastrophic failure was observed when an alloy had both a relatively high areal grain boundary coverage by film-like β phase, and a reticulately interconnected plate-like β phase in the grain interior. Hydrogen bubble formation was also observed, in relation to the progress of crack-tip corrosion. The main corrosion product was identified as Al(OH)3, based on its linear absorption coefficient. The respective amounts of corrosion products and hydrogen gas in the gas bubbles, and the pH value of the aqueous solution, were accurately measured during in-situ tensile testing, enabling estimation of the local elevation of hydrogen content in the crack-tip vicinity. Finally, a quantitative criterion for the occurrence of hydrogen embrittlement in inter-β ligaments is discussed, together with the applicability of the findings to the prevention of SCC.
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U2 - 10.1016/j.corsci.2021.109343
DO - 10.1016/j.corsci.2021.109343
M3 - Article
AN - SCOPUS:85102141271
VL - 184
JO - Corrosion Science
JF - Corrosion Science
SN - 0010-938X
M1 - 109343
ER -