Mechanical Properties Charicterization Of Thermal Oxidation TC4

Titanium and titanium alloys are widely used in many fields,because of their high strength-to-weight,excellent corrosion resistance and bilcompatibility.However the poor tribological behavior caused by high and unstable friction coefficients,severe adhesive wear and a strong tendency to seize,as well as the poor corrosion resistance in some aggressive environments have seriously restricted extensive applications of titanium.Surface engineering methods have proved to be the most promising way to improve the surface performance of titanium.In this paper,the thermal oxidation layer was prepared on the surface of TC4 titanium alloy by 700? and 10 h thermal oxidation process,and the composition,hardness,wear resistance and corrosion resistance were analyzed.The effects of thermal oxidation process parameters on the static and dynamic mechanical properties of titanium alloys were investigated by means of Nano Indentation,static compression and dynamic compression.Based on the experimental data,the Johnson-Cook constitutive equation and bilinear elastoplastic model are fitted.Finally,the impact process is simulated by ANSYS/LS-DYNA,and the fracture mechanism and the influence of the oxide layer on the impact deformation process is analyzed.In addition,this paper studied the thermal oxidation temperature(600-750?)10 h,700 at different oxidation time(10-50 h)static effect of dynamic mechanical properties of TC4 titanium alloy.The main results are as follows:(1)Through 700/10 h thermal oxidation,the oxide film rutile Ti O2 is formed on the surface of TC4 titanium alloy,and the surface color from white to black,and the microhardness increased from 300 HV0.05 to 600 HV0.05.The friction and wear properties were improved,and the corrosion was delayed.(2)The hardness and elastic modulus of TC4 titanium alloy were improved after 700? and 10 h heat treatment.The results show that 700?/10 h titanium alloy can improve the strain rate and yield strength at room temperature under quasi static(3)The strain rate sensitivity of TC4 substrate and 700?/10 h thermal oxidation TC4 are relatively low.The dynamic strain hardening effect of thermal oxidation TC4 was increased.At low strain rate,the impact plasticity of 700?/10 h thermal oxidation TC4 increases,and the impact plasticity decreases and becomes worse with the increase of strain rate.(4)The effects of different thermal oxidation conditions on the yield strength and strain hardening rate of static materials were investigated.The results show that the TC4 titanium alloy has the best quasi static mechanical properties after 700?and 10 h oxidation treatment.(5)Different thermal oxidation treatments have no effect on the dynamic yield strength,improve the dynamic stress of the material and change the impact ductility of the material.The results show that the TC4 titanium alloy after 700? and 30 h treatment has better dynamic performance.(6)Johnson-Cook constitutive model can predict the plastic flow stress of TC4 titanium alloy at room temperature.The oxide layer formed by thermal oxidation can play a buffer role at low strain rate,which can improve the performance of the material.When the strain rate is too large,the oxide layer on the surface of the material will break down to form a crack,which will lead to the destruction of the material.