Corrosion Fatigue Properties Of UFG CP Ti Prepared By Compound Refinement

As the most promising engineering material,pure titanium has many good characteristics,such as low density,shape memory,non-magnetic properties,and good biocompatibility.However,due to its low strength,poor wear resistance and other shortcomings,the application of pure titanium is limited.In this paper,UFG CP Ti was prepared at room temperature through the ECAP+CR+RS composite refinement process.The ultrafine crystal industry was studied by using scanning electron microscope,transmission electron microscope,room temperature tensile test,high cycle corrosion fatigue test and simulation analysis.Fatigue and fracture mechanism of UFG CP Ti under different stress loading conditions in simulated seawater environment.Give the result as follows:Compared with UFG CP Ti and pure titanium,the UFG CP Ti prepared by the compound refinement process are significantly refined,and its yield strength is increased from 488 MPa to 908.5 MPa.Under the conditions of constant temperature of water bath 17.9±0.5?,3.5%NaCl(PH=8.1±0.2),|=25Hz,stress ratio R=-1,the corrosion fatigue limit of UFG CP Ti is close to the conventional fatigue limit.The stress-life mathematical model is:log?_a=-0.03952 log N_f+2.88201,with a cycle of 10~7 cycles as The ultimate corrosion fatigue limit is about 403 MPa,and the ratio of fatigue limit to tensile limit is about 0.43.Due to the short time of the experiment,the UFG CP Ti has excellent corrosion fatigue performance.The main damage mechanism of UFG CP Ti is dislocation slip.By comparison,the multiphysics simulation software COMSOL Multiphysics was selected to simulate the corrosion fatigue of composite refined UFG CP Ti when it was in the environment of 3.5%NaCl solution.In this software,through the input of data such as sample shape,material properties,loading stress size and method,boundary constraints,etc.,the material fracture status and cycle number under each stress loading state are obtained,and then the S-N curve is drawn.Comparing the simulation data with the actual experimental results,the UFG CP Ti has a very high agreement between the S-N curve of the simulation and the actual corrosion fatigue test.The corrosion fatigue limit is 0.439s_b(Year 0),0.383s_b(Year 2),0.342s_b(Year 4),0.295s_b(Year 6),0.246s_b(Year 8),0.206s_b(Year 10),as the simulation progresses,the corrosion fatigue limit of the material decreases year by year.Since the year,2,4,6,8,and 10 years,it has gradually decreased by 12.76%,22.10%,32.80%,43.96%,53.08%,after a long time of simulation,it was found that the material still has a higher corrosion fatigue limit.