Study On Electrochemical Plasticization And Friction Mechanism Of Titanium Alloy Surface

As an important material in aerospace,civil medicine and other fields,titanium alloy tubes,rods and wires with excellent properties play an important role.This thesis aims at the existing problems of surface work hardening,low processing efficiency and poor product surface quality during the cold drawing process of titanium alloys,and studies the electrochemical plasticization mechanism of titanium alloys in corrosive media and the influence mechanism of surface tribological behavior.It is expected to provide theoretical guidance for the development of electrochemical cold drawing technology of titanium alloys,promote its application,and provide technical support for the high efficiency,low energy consumption and high quality processing of titanium alloys and other difficult-to-deform alloys.In this thesis,TC4 alloy is selected as the research object to study the formation process of plasticized layer on the surface of titanium alloy under the combined action of chemical corrosion current and stress.This study observes the electrochemical state,microstructure,microhardness,friction coefficient,wear rate and wear scar morphology of the alloy surfaces during the plasticization process,analyzes the electrochemical plasticization mechanism of TC4 alloy surface,and discusses the influence of different corrosion parameters(medium,concentration,voltage,etc.)on the tribological properties of the plasticized surfaces.The main research methods and contents of this thesis are as follows:(1)This thesis uses the CHI604E electrochemical workstation to obtain the electrochemical curves of the TC4 samples under different corrosion conditions,and analyzes the influence of different parameters on the electrochemical corrosion behavior of TC4 alloy by studying the changes of the sample open circuit potential and corrosion current under the conditions of static corrosion,friction corrosion,and friction corrosion under external potential.The results show that both friction and the applied anode potential can affect the surface passivation state and corrosion-behavior of the TC4 alloy sample.The local plastic deformation and anode potential in the contact area promote the anodic dissolution at the wear scar of the sample,making the open circuit potential(OCP)negative shift and corrosion current(icorr)increase,affecting the corrosion tendency and reaction rate.(2)A variety of analysis and detection methods were used to further study the influence of different corrosion parameters on the structure and mechanical properties of the surface corrosion layer,and explore the film formation process and plasticization mechanism of TC4 alloy in acidic corrosion solution.In this thesis,the morphology of the corroded surface was observed,the corrosion components were detected and analyzed,and the hardness and elastic modulus of the electrochemically corroded surface were measured.The results show that under the combined action of chemical corrosion and applied potential anodic polarization,the corrosion reaction is no longer inhibited,and the anodic dissolution and surface passivation of the TC4 matrix reach a dynamic balance,forming a corrosion defect area with surface cavities.The surface of TC4 alloy shows the phenomenon of electrochemical plasticization with reduction of mechanical properties and elastic modulus.(3)On the basis of studying the corrosion behavior and plasticization phenomenon under different parameters,this study continues to observe the friction coefficient,wear rate,and wear morphology of TC4 samples under different friction environment parameters(media type,media concentration,applied potential,sliding speed),and analyzes the influence of different electrochemical surface plasticized layers on the tribological properties of TC4.By studying the phase change law of the plasticized layer in the friction process,the synergistic interaction between surface plasticization and friction and the wear mechanism are discussed.The results show that different corrosion treatments affect the tribological properties of TC4 alloy surface.The vacancies formed in the frictional contact area under anodic dissolution will be attracted and migrated by the deformation dislocations during friction deformation,showing extra plasticity in the deformation direction,reducing the friction shear resistance and forming an easy shear corrosion layer play a good anti-friction lubrication effect.