Preparation Of TC4 Titanium Alloy Heat Dissipation Structure SLM For Aviation And Study On Heat Treatment Strengthening And Microstructure Properties

Ti6Al4V（TC4）titanium alloy has the advantages of low density,high specific stiffness,corrosion resistance and fatigue resistance,and is widely used in aircraft components.The traditional TC4 titanium alloy manufacturing process has the disadvantages of high processing energy consumption,low material utilization,long forging cycle time and difficulty in forming complex structural parts,which hinders the application and development of TC4 titanium alloy.SLM（Selective Laser Melting,SLM）provides a new way of thinking for the manufacture of complex structural parts with short production cycles,high material utilisation and high precision.Therefore,SLM parts need to be post-treated to achieve serviceability.Taking the heat dissipation structure of TC4 prepared by laser selective melting technologyas the research object,this paper mainly analyzes the microstructure and properties of alloy materials in the heat dissipation holes and outer areas before and after heat treatment by designing different heat treatment processes,including metallographic and X-ray diffraction（XRD）,scanning electron microscopy（SEM）,microhardness and electrochemical corrosion.On this foundation,the effect of different heat treatment processes on the microstructure structure,phase transformation,microhardness and electrochemical corrosion performance of TC4 heat dissipation structure prepared by laser selective melting technology was explored,and the following results were obtained:The TC4 heat dissipation structure prepared by SLM is composed of a fine needle-likeα’phase and a small number ofβphases,with a"cluster"composed of a sheetα’phase in the near inner pore area,while the outerα’phase is scattered on theβsubstrate.There are uneven tissues near and outside the heat dissipation holes.The hardness fluctuation range of the surface is large(55.523HV_0.2)and the inner and outer hardness is large.After heat treatment,the microstructure and properties are improved:Using the heat treatment process of annealing,it is found that with the increase of annealingtemperature and holding time,the structure is coarsed,the hardness rises first and then falls,and the corrosion resistance is enhanced.Among them,when the annealing temperature is900°C,theα’phase is basically converted intoαphase,the content of theβphase increases,the grain and structure of the heat dissipation structure are uniform,which is most significant in the near inner hole area;the hardness is significantly reduced,and the hardness difference around and outside the heat dissipation hole is reduced to(12.42HV_0.2).With the heat treatment process of solid solution,the mesh basket structure is formed inside,and with the increase of solution temperature,the grain width andβphase content increase,the hardness decreases,and the corrosiveness is enhanced.Among them,when the solution temperature is 980°C,there is a small number of rod-shapedαphases around the heat dissipation holes of the heat dissipation structure;The hardness is slightly reduced compared with the original state,and the difference between the inner and outer hardness is(20.4HV_0.2);the corrosion resistance is better than the original state but lower than the annealing process at900°C.Using the heat treatment process of solution+aging,the structure is mainly uniformly dispersed（α+β）phase,the hardness is reduced,and the corrosion is slightly worse.Among them,after 970°C/1h/WC+550°C/4h/AC treatment,the difference between the inner and outer tissues of the heat dissipation structure was the smallest in other heat treatment processes.The hardness is reduced,the difference between the inner and outer hardness is not much(8HV_0.2);the electrochemical corrosion potential is negatively shifted,and the corrosion performance of the TC4 heat dissipation structure is slightly reduced compared with the original state,and the comprehensive performance is obtained.