Improved strength and ductility of rapidly solidified 2195 alloy by pre-rolling combined with double aging and interrupted aging

Abstract

Pre-rolling combined with double aging (DAT8) and interrupted aging (IAT8) were carried out to improve the mechanical properties of rapidly solidified 2195 Al–Cu–Li alloy. For the DAT8 treatment (4% pre-rolling + 120 °C/12 h + 165 °C/16 h), low aging temperature (120 °C) in the first stage forms abundant δ′ phase, which grows into well-dispersed T1 plates in the second stage (165 °C). The IAT8 treatment (165 °C/2 h + 4% pre-rolling + 65 °C/5 day + 165 °C/16 h) first produces some small GP zones, which are connected to dislocations generated by pre-rolling. Subsequent long-term low-temperature aging (65 °C/5d) results in the enrichment of Cu, Mg, Ag and Li atoms on dislocations, significantly enhancing the precipitation driving force of the T1 phase. The results show that DAT8 and IAT8 treatments simultaneously improve the strength and ductility of the alloy. The increased strength is mainly due to the dense precipitation of the T1 phase, generating higher precipitation strengthening, as well as the introduction of high dislocation density, yielding strain strengthening. The improved ductility is attributed to the fine and well-dispersed T1 phase, decreasing the incongruous deformation between precipitates and matrix, and suppressing the formation of precipitation free zone (PFZ), weakening local stress concentration at sub-grain boundaries.