Study On Selective Laser Melting Forming Of TC4 Titanium Alloy And Mechanism Of Surface Magnetic Finishing

With the rapid development of aerospace technology,the manufacturing requirements for aerospace titanium alloy components have become increasingly high.Traditional methods such as forging,casting,machining,and welding cannot meet the needs of today’s aerospace field.Therefore,more advanced technologies and methods have emerged as the times require.Selective laser melting（SLM）forming TC4 titanium alloy complex components provides an effective way to solve the above problems.However,SLM-formed TC4 titanium alloy components have problems such as unstable microstructure properties and poor surface quality,which is difficult to meet the requirements of high precision and high quality.In this paper,TC4 titanium alloy,a widely used material in the aerospace field,is selected to carry out SLM forming process and performance research,optimize the forming process parameters of TC4 titanium alloy formed by SLM,and study the magnetic finishing mechanism and surface quality of TC4titanium alloy formed by SLM.The main research contents and innovations of this paper are as follows:（1）Research on SLM forming process of TC4 titanium alloy powder.It mainly includes the optimization of SLM forming parameters of TC4 titanium alloy and the sample forming.The optimal forming parameters of TC4 titanium alloy SLM were determined to be laser power 275 W,scanning speed of 1100 mm/s and scanning distance of 120μm.The density of TC4 titanium alloy specimens formed under optimal forming parameters can reach up to 99.55%,and the average surface roughness Ra value of the side of the formed specimen is about 6μm.Due to the large residual tensile stress on the surface of the SLM formed sample,compared with the rolled TC4 titanium alloy sample after heat treatment,the internal microstructure of the SLM formed sample is more complex,and the density is low,which is not easy to be processed.（2）The research of magnetic finishing SLM forming TC4 titanium alloy mainly includes the design of magnetic finishing TC4 titanium alloy system,the optimization of magnetic finishing process parameters of SLM forming TC4 titanium alloy,and the research of surface quality of magnetic finishing SLM forming TC4 titanium alloy sample.The optimum magnetic finishing process parameters of TC4 titanium alloy formed by SLM are determined as follows:the spindle speed is 1000.00 r/min,the machining clearance is 1.50 mm,and the feed speed is 15.00 mm/min.After 48 minutes of magnetic finishing,the surface roughness of SLM sample decreased from Ra 0.6μm after rough grinding to Ra 0.065μm,The residual stress on the surface of the specimen was changed from tensile stress+297.4 Mpa to compressive stress of-237.8 Mpa,and the surface quality of the specimen was significantly improved,showing a mirror effect.（3）The removal mechanism of magnetic polishing SLM forming TC4 titanium alloy material is the removal of magnetic abrasive micro-cutting plasticity,the shear and extrusion of Al₂O₃ceramic abrasive phase and abrasive matrix,and the weak chemical corrosion of slurry,which work synergistically on the surface of SLM formed TC4titanium alloy specimen to achieve the purpose of magnetic polishing processing.The final surface micro-topography of the sample is the nano scale disorderly distributed small scratches produced by plastic removal.The surface quality of the TC4 titanium alloy sample formed by SLM has been significantly improved after magnetic finishing.This paper aims at the problems of low density and poor surface quality of TC4titanium alloy components formed by SLM,The forming process,magnetic finishing process and removal mechanism of TC4 titanium alloy formed by SLM were studied,The sample of TC4 titanium alloy formed by SLM with uniform and stable internal structure and properties and high surface quality has been obtained,which has important theoretical significance and engineering application value.