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Investigation of microstructure evolution after post-weld heat treatment and cryogenic fracture toughness of the weld metal of AA2219 VPTIG joints

In this work, the effect of post-weld heat treatment (solid solution+artificial aging) on the microstructure and cryogenic fracture toughness of the weld metal of VPTIG welded AA2219 joints were investigated by using crack tip opening displacement (CTOD) test method. The samples were divided into th...

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Published in:Materials & design 2017-01, Vol.113, p.54-59
Main Authors: Lin, Yi Tong, Wang, Ming Chao, Zhang, Yu, He, Ya Zhang, Wang, Dong Po
Format: Article
Language:English
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Summary:In this work, the effect of post-weld heat treatment (solid solution+artificial aging) on the microstructure and cryogenic fracture toughness of the weld metal of VPTIG welded AA2219 joints were investigated by using crack tip opening displacement (CTOD) test method. The samples were divided into three types: (i) the weld metal of as-welded joint, marked as sample A; (ii) the weld metal of post-weld heat treated joint, marked as sample B; (iii) the base metal used for comparison, marked as BM. The results showed that the solution treatment dissolved θ phases, and the artificial aging treatment re-precipitated θ' phases. After post-weld heat treatment, the strength of weld metal was improved, accompanied with a little bit of decrease in the plasticity and fracture toughness. No matter what kind of sample types, compared to 298K, the strength tested at 77K was higher due to the weaker lattice vibration frequency and lower energy fluctuation. Besides, the plasticity was also higher at 77K than that at 298K, because the Peierls-Nabarro force was not sensitive to temperatures. Thus, the fracture toughness was also better at 77K. [Display omitted] •Aluminum alloy 2219 was welded by variable polarity tungsten inert gas arc welding.•The effect of post-weld heat treatment on morphologies of precipitates was studied in detail.•The cryogenic fracture toughness of the weld metal was investigated by crack tip opening displacement tests.•The crack tip opening displacement values at 77K were nearly 20% higher than those at 298K.
ISSN:0264-1275
1873-4197
DOI:10.1016/j.matdes.2016.10.010