Study On The Formation Mechanism Of High Temperature Oxide Film On Cutting Surface Of Titanium Alloy

Titanium alloys are widely used in many fields such as aerospace,medical and chemical industries due to their high strength,strong corrosion resistance and high heat resistance.The high hardness of the material itself makes it difficult to process.In the cutting process,the low heat transfer of the titanium alloy itself will generate a large amount of cutting heat,resulting in the formation of an oxide film on the cutting surface,which affects the material properties of the workpiece itself.Therefore,it is necessary to study the formation mechanism of high temperature oxide film on the cutting surface of titanium alloy.This time,pure titanium TA2 and TC4 titanium alloys are used as the research objects.Through the inspection and observation of the cutting surface after turning,the first principles and slow positron beam technology are used to treat titanium alloys in the direction of atom bonding and electron transfer.The formation mechanism of oxide film at high temperature was studied.The main research contents and results are as follows:（1）The single factor experiment method was used to conduct turning experiments on pure titanium TA2 and TC4 titanium alloy bars.In the experiment,the temperature during the cutting process was detected by an infrared thermometer.The Gibbs free energy calculation is performed on the metal oxidation reaction of the metal elements in the two materials.Studies have shown that during the cutting process of pure titanium TA2 and TC4 titanium alloys,the metal elements in the two materials can react with oxygen to form oxides.Pure titanium TA2 forms an oxide film during the cutting process,and the main elements of the oxide film formed during the cutting process are Al2O3,Ti O2 and V2O5.（2）Metallographic experiments were performed on the metal cutting surfaces of pure titanium TA2 and TC4 titanium alloys to observe their surface morphology and microstructure.Studies have shown that the oxide film of pure titanium TA2 and TC4titanium alloys show a huge color difference under the same cutting conditions.The reason is that the TC4 titanium alloy contains Al and V elements,and the oxide film produced has a large difference in composition.The thickness of the formed oxide film is different.The plastic deformation layer caused by the cutting force has no effect on the color of the oxide film.（3）Perform first-principles calculations on the oxidation process of pure titanium TA2 and TC4 titanium alloys,and explore the formation mechanism of the oxide film of titanium alloys during the oxidation process.Studies have shown that oxygen atoms have good reactivity on the surface of pure titanium metal and TC4titanium alloy,and both penetrate further into the matrix.TC4 titanium alloy is easier to oxidize with oxygen atoms under the same conditions,with stronger permeability and thicker oxide film.TC4 titanium alloy preferentially combines with aluminum atoms to form Al₂O₃during the oxidation process,and then continues to penetrate into the TC4titanium alloy system to combine with titanium and vanadium atoms to form oxides.（4）The slow positron beam experiment was performed on the cutting surface of pure titanium TA2 and TC4 titanium alloys to detect the thickness of oxidation during the cutting process.Studies have shown that with the increase of cutting speed,the thickness of the oxide film of the same material gradually increases,and the color of the oxide film becomes darker as the thickness increases.At the same cutting speed,TC4titanium alloy is easier to react with oxygen to form an oxide film than pure titanium TA2,that is,the thickness of the oxide film is larger.