| Electron Beam Fuse Deposition(EBF)is a new additive manufacturing technology based on the wire as raw material,Electron Beam as the heat source,and net forming under a vacuum environment.It is widely used in aerospace,Marine engineering,mechanical chemical industry,biomedical and other fields.304 stainless steel is the most widely used austenitic stainless steel,high strength,wear resistance,corrosion resistance,good surface gloss,and has good comprehensive performance and welding performance.In 304 stainless steel application scenarios,the thin-walled structure and block structure are common.In this paper,EBF 304 stainless steel is formed for these two different structures.The mechanical properties of 304 stainless steel under different structures are studied by comparing different processes.The penetration ability of the electron beam is determined by the acceleration voltage of the electron beam.During the shaping of the thin-wall structure,the influence of different acceleration voltages(50k V,60 k V,70 k V)on the interlayer bonding is studied and the mechanical properties and anisotropy of the thin-wall structure under different acceleration voltages are compared.The mechanical properties and anisotropy parameters of the formed thin-wall structure were obtained.The block structure was shaped by two forming paths of "bow-shaped" and "alternating bow-shaped",and the mechanical properties and anisotropy of the block structure were studied.The samples were heat treated by three heat treatment processes: 850 ℃/air cooling,1050 ℃/air cooling,and 1050 ℃/water cooling.The effects of different heat treatment processes on their formability and microstructure were studied and analyzed.The mechanical properties of the EBF-shaped 304 stainless steel thin-walled structure are anisotropic.When the acceleration voltage is 60 k V,the mechanical properties are the best and the anisotropy is the weakest.The tensile strength and yield strength in the horizontal direction are 1092 MPa and 1081 MPa respectively,and the tensile strength and yield strength in the vertical direction are 1099 MPa and 1035 MPa respectively.It is found that the mechanical properties of products with block structure also exhibit anisotropy in the formed block structure.Strength in different directions is X direction,Y direction,and Z direction from superior to inferior.It is found that the microstructure of 304 stainless steel products formed by the EBF method has certain magnetism due to the large amount of martensite in the formed thin-walled and block structure products.The heat treatment process decreases the density of the 304 stainless steel sample,which leads to a slight decrease in strength.However,by observing the microstructures,it is found that martensite decreases and the corresponding magnetic properties decrease after heat treatment. |
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