The identification of hydrogen trapping states in an Al-Li-Cu-Zr alloy using thermal desorption spectroscopy
Thermal desorption spectroscopy (TDS) was utilized to identify several metallurgical states in an Al-2Li - 2Cu-0.1Zr (wt pct) alloy, which trap absorbed hydrogen. Six distinct metallurgical desorption states for hydrogen were observed for tempers varying from the T3 to peak aged condition. Lower energy thermal desorption states were correlated with interstitial sites, lithium in solid solution, and {delta}{prime} (Al{sub 3}Li) precipitates. These states have trap-binding energies {le}25.2 kJ/mol. Under the charging conditions utilized, approximately 4 pct of the total (e.g., trapped and lattice) hydrogen content was associated with interstitial sites, consistent with the view that the intrinsic lattice solubility of hydrogen in aluminum is very low. In contrast, dislocations, grain boundaries, and T{sub 1} (Al{sub 2}CuLi) particles were found to be higher energy-trap states with trap-binding energies {gt}31.7 kJ/mol. Approximately 78 pct of all absorbed hydrogen occupied these states. Moreover, greater than 13 pct of the available trap sites at grain boundaries were occupied. Such a high hydrogen coverage at grain-boundary sites supports the notion that hydrogen contributes to grain-boundary environmental cracking in Al-Li-Cu-Zr alloys. Also, it points out the error in assuming that hydrogen cannot play a major role in cracking of Al-based alloys due to the low lattice solubility.
- Research Organization:
- Univ. of Virginia, Charlottesville, VA (US)
- OSTI ID:
- 20014055
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 31, Issue 1; Other Information: PBD: Jan 2000; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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