Assessing the fatigue crack growth behavior of highly sensitized AA5456-H116 under cathodic polarization

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:792

Article

Harris, Zachary D.¹  Dubas, Erin M.¹  Schrock, David J.²  Locke, Jenifer S. (Warner)²  Burns, James T.¹ 

[1] Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22904 USA

[2] Ohio State Univ, Dept Mat Sci & Engn, 116 W 19Th Ave, Columbus, OH 43210 USA

关键词: Corrosion fatigue;    Cathodic corrosion-induced blunting;    Al-Mg alloys;    Hydrogen embrittlement;   

DOI  :  10.1016/j.msea.2020.139792

来源: Elsevier

【 摘 要 】

Fatigue crack growth experiments were conducted on highly sensitized AA5456-H116 in laboratory air and 0.6 M NaCl at two applied potentials (-900 mV(SCE) and -1300 mV(SCE); vs. saturated calomel electrode) using frequencies of 5 and 0.1 Hz. At 5 Hz, the fatigue crack growth rate (da/dN) was similar between -900 mV(SCE) and -1300 mV(SCE) (similar to 1.5 x 10(-4) mm/cycle), which were both approximately 10-fold faster than the da/dN measured in laboratory air. However, significant differences in da/dN were observed between -900 and -1300 mV(SCE) for testing at 0.1 Hz. Specifically, while a nominally similar da/dN to the 5 Hz data was observed for -900 mV(SCE), a 1000-fold decrease in da/dN was noted for -1300 mV(SCE) at 0.1 Hz. Microscopy of the crack tip region on interrupted fatigue experiments conducted at -1300 mV(SCE) revealed significant blunting of the crack tip at 0.1 Hz, while the crack tip cycled at 5 Hz remained sharp. A stepped potential experiment demonstrated that the measured da/dN at -1100 mV(SCE) decreased by multiple orders of magnitude when this potential was approached from the cathodic versus the anodic direction. Collectively, these data suggest a salient role of corrosion-induced blunting on the measured da/dN for highly sensitized AA5xxx-series alloys immersed in marine environments at highly cathodic potentials and low loading frequency.

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