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

摘要

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. phases, and the artificial aging treatment re-precipitated.' 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 298 K, the strength tested at 77 K was higher due to the weaker lattice vibration frequency and lower energy fluctuation. Besides, the plasticity was also higher at 77 K than that at 298 K, because the Peierls-Nabarro force was not sensitive to temperatures. Thus, the fracture toughness was also better at 77 K. (C) 2016 Elsevier Ltd. All rights reserved.