Investigation On Microstructure And Properties Of TC4 Titanium Alloy Fabricated By Rapid Additive Manufacturing

Titanium alloy is an important application material of aero-engine,its manufacturing process is one of the important standards to measure the level of a national aviation industry.Conventional manufacturing methods not meet products of rapid and complex,rapid manufacturing method based on additive provides an effective way for this problem.In this thesis,the effects of alloy phase structure,microstructure and properties on different rapid manufacturing TC4 titanium alloys were studied.The main research contents are as follows:(1)Rapid additive manufacturing basis.For the rapid casting process,the filling and solidification processes were analyzed,and the defect prediction basis was given.Based on the laser,powder characteristics and rapid solidification forming process,the selective laser melting forming mechanism was analyzed.The equipment,process and detection methods used in rapid manufacturing were described to provide a theoretical basis for systematic research.(2)Microstructure and properties of rapid casting TC4 titanium alloy.The temperature field,cooling rate,phase composition,microstructure,mechanical properties,high temperature durability and friction and wear properties were systematically studied by numerical simulation and experiment.The effect of mold on microstructure and properties of the alloy was investigated.It was found that the cooling rate of graphite mold was higher than ceramic mold and increased by 52.04%.At the same time,texture of ceramic mold was strong and orientation was obvious,the toughness and high temperature durability were higher than graphite mold,and the rapid casting process of ceramic mold was more suitable.(3)Microstructure and properties of laser selective melting TC4 titanium alloy.The effects of laser energy density and forming direction on microstructure and properties of TC4 titanium alloy were analyzed.It was found that the increase of line laser energy density,the life of molten pool was prolonged and the maximum cooling rate was reduced.Further optimizing the process,the increase of bulk laser energy density,the density first increased,then decreased,when the bulk laser energy density was 101.85 J/mm3,the strength and plasticity were better.After optimizing the process,it was found that the forming direction had a significant impact on the microstructure and properties,the original ? grain in the cross section was equiaxed and refined,and the strength,hardness and wear resistance had different degrees of anisotropy,the optimal forming process was obtained by performance control,which provides a basic reference for the microstructure and performance improvement of titanium alloy prepared by rapid manufacturing technology.