Abstract:The water-quenched (WQ) 2195 Al-Li alloy was subjected to stretching at different temperatures, from room temperature (RT) to -196 °C (CT), to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties. The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric (DSC) tests and electron microscopy observation. The results show that -196 ℃ deformation produces a high dislocation density, which promotes the precipitation of the T1 phase and refines its sizes significantly. In addition, the grain boundary precipitates (GBPs) of -196 °C-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors, which increases the ductility. In comparison, the strength remains nearly constant. Thus, it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.

Key words: Al-Li alloy; cryogenic stretching; T1 phase; precipitation kinetics; grain boundary precipitates