The effects of different annealing temperature and time on the microstructural evolution and mechanical properties of the oxygen free copper tube were investigated by OM

TEM

SEM and universal tensile tester.The results reveal that:the high energy and high density dislocation of the as-deformed sample are evolved into thin dislocation walls

subgrain boundaries and then high angle grain boundaries with annealing at 260 ℃ or 300 ℃for 60 min

resulting in low density dislocation structure.After annealing at 300℃

recovery and recrystallization are fully completed.The tensile strength

yield strength and hardness are decreased with temperature increase

while the elongation is increased.Within the annealing temperature range of 300 ℃to 460 ℃

the change of mechanical properties of the copper tube can be ignored.Increasing the annealing time at 300 ℃from 10 min to 60 min

recrystallization is induced gradually

and the tensile strength

yield strength and hardness are decreased

while elongation is increased.With annealing for 60 min

recrystallization is finished

and the tensile fracture morphology is changed from quasi-cleavage surface

tearing edge and dimple characteristics to equiaxial dimples.Compared with those of as-deformed sample

the tensile strength

yield strength and hardness of the copper tube are decreased by 39%

68.5%and 53.1%

respectively

and the elongation is increased from1.2%to 50%.With annealing time more than 60 min

the grain size is increased slightly before reached a stable value

showing an insignificant effect on the mechanical properties.