Behavior of Hydrogen in Al-4%Mg Alloys during Heat Treatment

Abstract:

The effect of the annealing atmosphere, the annealing temperature etc. on the hydrogen behavior in several Al-4% Mg alloys during heat treatment, was investigated. The results have shown that the hydrogen content in the as-cast slab is uniform, while the hydrogen content in the slab tends to be higher near the surface than in the interior after annealing. Such a tendency becomes more marked when annealing time is prolonged and Si and Fe content is lowered. The condensation of hydrogen near the surface can be seen only when it is annealed in a wet atmosphere. When annealed in a dry atmosphere, the hydrogen content near the surface becomes lower than in the center of the specimen. The hydrogen in Al-Mg alloys tends to be released to outside intrinsically at temperatures around 400°C and above. It is revealed that oxide film formed on the surface prevents the hydrogen from being released to outside.

• Periodical: Materials Science Forum (Volumes 539-543)
• Pages: 305-310
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.539-543.305
• Online since: March 2007
• Authors: Hidetoshi Umeda, Goroh Itoh, Yoshinori Kato
• Keywords: Al-Mg-Si Alloy, Blister, Diffusion, Heat Treatment, Hydrogen

References

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40 50 100 150 200 Hydrogen content (ppm) as-cast Distance from the surface, d/mm 540°C, 24h 540°C, 0h.

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40 50 100 150 200 Hydrogen content (ppm) as-cast Distance from the surface, d/mm 540°C, 24h 540°C, 0h Fig. 2 Hydrogen content in specimen A before and after annealing as a function of the location.

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4 0 100 200 300 400 500 600 Hydrogen content (ppm) 4h 24h Temperature, T/°C.

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4 0 100 200 300 400 500 600 Hydrogen content (ppm) 4h 24h Temperature, T/°C Fig. 4 Change in hydrogen contents of specimen B annealed at each temperature for 4h or 24h. 0.

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2 Surface Center Hydrogen content(ppm) wet dry as-cast Center Surface Sample for hydrogen measurement 0.

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2 Surface Center Hydrogen content(ppm) wet dry as-cast Center Surface Sample for hydrogen measurement Fig. 3 Change in hydrogen content of specimen A cut in the shape of 100mm x 100mm x 100mm during annealing at 540˚C for 50h in the two atmospheres. 0.

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5 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 Thickness of oxide film, t/µm Hydrogen content (ppm) before annealing 540°C, 24h 0.

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5 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 Thickness of oxide film, t/µm Hydrogen content (ppm) before annealing 540°C, 24h Fig. 5 Change in hydrogen content of anodized specimens B during annealing at 540˚C for 24h as a function of film thickness.