The effects of different aging time on microstructure and properties of hot-extruded GH3625 alloy tube at 720℃ were investigated by means of scanning electron microscopy（SEM）

energy-dispersive spectrometry（EDS）and Image-Pro plus metallographic analysis software.The results indicate that the M

23

C

6

γ" phase andδphase are mainly precipitated in the GH3625 alloy at 720℃ during long term aging

and the strength and hardness of GH3625 alloy are increased

however

the plasticity is decreased drastically.With the increase of aging time

some M

23

C

6

phases are transformed into M

6

C

and most of theγ"phases are transformed into acicularδphase.In addition

after aging for 5 000 h

theδphase is changed from long acicular to long rod-like

weakening strengthening effect ofγ" phase.Theδphase is grown up with aging time and the average growth rate length 5.9×10

8

nm

3

/h

following LSW theory

while the average width of coarsening is deviated from the LSW theory.