Research On Forming Accuracy And Mechanical Properties Of SLM Forming Inclined Titanium Alloy Thin-wall Structure

Due to the high specific strength,high corrosion resistance and biocompatibility of titanium alloy,it is widely used in aerospace,biomedical and other fields.However,it is difficult to process this alloy by the traditional processing method because of the large deformation resistance and low thermal conductivity of titanium alloy.With the development of complex structures in aerospace and other fields,traditional processing technology has become more and more difficult to meet the needs of the industry.Selective Laser Melting(SLM),as an important branch of additive manufacturing technology,can quickly produce complex and precise metal structures.Parts designed based on SLM technology usually contain a large number of inclined thin-wall structures.When the inclined Angle of the thin-wall structure is small,SLM forming requires the design of support structure.When the thin-walled structure is inside the part,it is difficult or impossible to remove the support structure.Therefore,in this paper,formability and mechanical properties of inclined thin-wall structure are studied,and Ti6Al4 V is used as the raw material to study the influence of various structural characteristic parameters and spatial placement of SLM formed thin-wall structure.The main research contents are as follows:(1)The research on the dimensional accuracy of thin-wall structure formed by SLM is carried out,and the forming characteristics of thin-wall structure under different sampling locations,different wall thicknesses,different tilt angles and spatial placement characteristics are analyzed.The forming accuracy of SLM thin wall structure was investigated,and the mapping relationship of thin wall structure feature-space placement feature-forming quality was established.It is found that the forming Angle of thin-wall structure has a great influence on the thickness and rough value of downdip surface.The rough value of the downdip surface of the thin wall of parallel scraper increases with the increase of growing height.(2)The mechanical properties of thin-walled structures formed by SLM are studied,and the influences of different sampling locations,different wall thicknesses,different tilt angles and spatial placement characteristics on the mechanical properties of thin-walled structures are analyzed.By observing the fracture morphology of thin wall structure with different characteristic parameters,the fracture characteristics of thin wall Ti6Al4 V were analyzed.It was found that the thin-wall fracture with inclined Angle present two kinds of macro morphology,brittle zone and ductile zone,and the ductile zone was always close to the overhanging side.Secondly,the tensile strength anisotropy of thin-walled structures was analyzed by exploring the strength difference ratio under different characteristic parameters.(3)The research on the defects and microstructure of thin-wall structure formed by SLM are studied.By comparing the distribution of defects and microstructure of solid and thin-wall structures,the differences between solid blocks and thin-wall structures formed by laser selective melting were explored,and the reasons for the changes in the mechanical properties of solid blocks and thin-wall structures were analyzed.It was found that the porosity of thin wall tends to decrease with the increase of thin wall inclination Angle.The orientation of the thin-walled columnar crystal was always parallel to the deposition direction,and the thickness of α slats increases with the increase of sample thickness,but the overall thickness is less than1μm.