| As a typical Additive Manufacturing technology,Electron Beam Solid Freeform Fabrication is suitable for rapid prototyping manufacturing of large active metal components due to its characteristics of high power,high efficiency and small beam spot.The manufacture of TC4 titanium alloy by EBF3 technology is an important means to achieve high performance and high material utilization in engineering applications.During the manufacturing of TC4 titanium alloy by EBF3,the high energy density of the electron beam caused the inhomogeneity and instability of the temperature field,which led to the complex changes of the stress field and affected the formability of the TC4 titanium alloy.Based on the above reasons,on the basis of thermal-coupling simulation,this paper further carried out the experimental study on the technology of EBF3 deposition of titanium alloy,and analyzed the macro and microstructure characteristics of EBF3 deposited TC4 titanium alloy.In this paper,"birth and death unit" technology of ANSYS software is used to simulate the single-channel multi-layer scanning process of the electron beam in the EBF3 test.In the study of temperature field of TC4 titanium alloy deposited by EBF3,the change of temperature field along the deposition height and electron beam scanning direction with time and the influence of process parameters on the temperature field of TC4 titanium alloy deposited by EBF3 were analyzed.Studies have shown that when the electron beam scans the same layer,the temperature in the middle of the deposited layer is relatively highest,and each point of the deposited layer in turn undergoes a thermal cycle process with the same trend.During the cooling process,the cooling rate of each layer is basically the same from fast to slow,and the heat accumulation in the middle of the deposit is relatively serious.The heat input during deposition is positively correlated with electron beam,but negatively correlated with the change of wire feeding speed and scanning speed.In the stress field study of TC4 titanium alloy manufactured by EBF3,the results of temperature field analysis were applied as structural loads to the nodes to achieve thermal-mechanical coupling,and the distribution of stress field with time during the deposition process was analyzed.Studies have shown that in the electron beam scanning area,the volume expansion of the alloy melt appears as compressive stress,while the deposited layer exhibits tensile stress.Secondly,when the electron beam increases,the surrounding metal has a smaller hindrance to the shrinkage of the deposited layer,and the stress value after the deposition is reduced;When the printing speed increases,the residual stress tends to increase.In the experimental study on the process of manufacturing TC4 titanium alloy by EBF3,the macroscopic morphology and microstructure of TC4 titanium alloy manufactured by EBF3 were investigated.Studies have shown that the height of the deposit decreases with the increase of the printing speed and increases with the increase of the wire feed speed,and the thick ? columnar crystals penetrate multiple deposition layers.The microstructure shows a lamellar structure as a whole,with a coarser structure at the bottom and a finer structure at the top.When the process parameters change,the morphology,phase content and orientation of the ? phase all change to a certain extent.In the EBF3 manufacturing TC4 titanium alloy process test study,the impact of changes in process parameters on the microhardness and defects of the sample was analyzed.Studies have shown that the change of microhardness is not obvious,basically fluctuating in the range of 21?48HRC,and with the increase of the deposition height,the microhardness has increased;At a faster printing speed,pores and unfused pores are randomly distributed in the area near the substrate. |
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