Corrosion fatigue crack growth behavior of a squeeze-cast Al-Si-Mg-Cu alloy with different precrack histories |
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Authors: | Kazuaki Shiozawa Shuming Sun |
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Affiliation: | (1) the Department of Mechanical Systems Engineering, Faculty of Engineering, Toyama University, 930 Toyama, Japan |
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Abstract: | Fatigue experiments have been performed on a squeeze-cast Al-Si-Mg-Cu alloy as a function of precrack history. The precracked
conditions were that the compact tension specimen was precracked with a relatively long through-thickness crack (about 6 mm)
in air, in aqueous 3 pct NaCl solution, and in air followed by hydrogen precharging. It was found that a relatively long through-thickness
crack can grow more rapidly than would be predicted by a traditional ΔK involving three stages under either a corrosion fatigue test after precracking in air or a hydrogen precharging experiment
followed by fatigue testing in air. The experimental evidence confirms that a hydrogen-assisted damage mechanism is mainly
responsible for the rapid growth phenomenon of a relatively long crack in a corrosive environment compared to the result of
fatigue testing in air after hydrogen precharging. The amount of hydrogen production in chemical-microstructure interaction
processes in a corrosion fatigue experiment and the effectiveness of hydrogen transport to the region ahead of the crack tip
determine the degree of hydrogen-assisted fatigue crack growth, which is controlled by the microstructure of the alloy and
the chemical attack on a sharp and fresh crack tip. |
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