Creep Behavior Of Commercially Pure Titanium Processed By ECAP After Cold Rolling And Rotary Swaging At Room Temperature

Pure Titanium'density is low,but it's melting point is high.And it's property of corrosion resistant and biocompatibility are well.So it is the idea implant material in medical.To make use of it's excellent properties,Ultra-fine grained(UFG)commercially pure Titanium(CP-Ti)was obtained by ECAP following with cold rolling and swaging.Microstructure of UFG CP-Ti were investigated by transmission electron microscope(TEM),scanning electron microscopy(SEM).Uniaxial tensile creep test and microhardness test was employed to study mechanical properties UFG CP-Ti.The main results of the research are as follows:The original grains was fragmented significantly and uniform processed by four passes of ECAP after cold rolling and swaging.The results showed that the yield strength of pure titanium was increased from 228 MPa to 800 MPa,and the increasing range was about 251% processed by ECAP after cold rolling and swaging.The annealing experiments results proved that the number of dislocations in the UFG CP-Ti was gradually reduced with the increase of annealing temperature.And the microstructure of UFG CP-Ti was restored when the annealing temperature was between 200°C and 400°C;When the annealing temperature was higher than 400°C,the recrystallization of UFG CP-Ti occured,the grain size growed rapidly,and the hardness decreased obviously.The tensile creep test of UFG CP-Ti at room temperature showed that under the condition of room temperature,stress was an important factor which affect the creep performance of UFG CP-Ti,with the increase of creep stress level,the steady creep rate of UFG CP-Ti was increased and the creep performance was deteriorated.In the range of 640Mpa~760Mpa,the creep deformation mechanism was dislocation slip mechanism,and the creep rupture type was ductile fracture.The steady creep rate and creep deformation of UFG CP-Ti after annealing at 200°C were reduced,while the creep life was increased and the creep resistance was improved.The creep finite element model of UFG CP-Ti at room temperature was established by numerical analysis of the creep characteristics of UFG CP-Ti at room temperature.The curve of creep strain vs time of UFG CP-Ti at room temperature was obtained and compared with the experimental results,which verifies the reliability of ABAQUS finite element simulation.