Abstract:Ultra-fine grain commercial pure (CP) Ti were processed by Equal channel angular pressing(ECAP) at room temperature and ECAP followed by cold rolling (CR).Effect of annealing temperature on microstructure and properties of ultra-fine grain commercial pure Ti were investigated by transmission electron microscopy (TEM),uniaxial tensile test and microhardness test.The results showed that,the average grain size of ultra-fine grain was about 130 nm ,and ultimate tensile strength was over 813 MPa;when annealing temperature was below 400℃,the organization had no obvious change.Ultimate tensile strength and microhardness slightly decreased.At the same time,elonggation increased.when annealing temperature was higher 400℃,grain size of ultra-fine grain CP Ti grew slowly,and dislocation density decreased.Ultimate tensile strength and microhardness decreased obviously when annealing temperature at 500℃, grain size of ultra-fine grain CP Ti grew rapidly,and average grain size was 2 μm.