Microstructure and properties of 2519 alloy during aging process at 180 ℃ were researched by means of optical microscopy （OM）

transmission electron microscopy（TEM）

scanning electron microscopy （SEM） and hardness test.The results showed that three aged stages are observed during the aging process of 2519 aluminum alloy at 180 ℃.The peak-aged time is 12 h.As the alloy for 5 h aging

a little amounts of discrete θ（or θ′） phase were precipitated from the grain boundaries

while no obvious precipitated phase in grain is found.Continuous chain-like θ（or θ′） phase precipitates were found on the grain boundaries and θ″ strength phase was commonly precipitated from the grain at peak-aged state.θ（or θ′） phase precipitates on the grain boundaries become coarse and spheroidization in a discrete state at aging for 20h

meanwhile the θ′ phase precipitated from the grain become coarse too.The elongation of the alloy was decreased with the increase of the aged time.