Study On Mechanical Properties Of Ti6Al4V Alloy Lattice Material By Selective Laser Melting

Lattice material is a new type of porous material with strict porosity and pore size constraints,which is periodically arranged by metal crystal cells.It has the characteristics of light weight,high strength and excellent functional properties,and is considered to be the most potential structure-function integrated material.Due to the large number of complex pore structure units,it is difficult to produce them accurately by traditional manufacturing techniques.Metal powder bed additive manufacturing technologies,such as Selective Laser Melting(SLM),are used to enable the rapid proto-forming of lattice materials with complex internal pore structures(including pore size,morphology and distribution),which can be accurately controlled by traditional manufacturing techniques.Especially suitable for the personalized preparation of Ti6A14V alloy lattice materials which are widely used in the field of biological implantation.However,the problems of microstructure disorder and surface adhesion powder in the formation of Ti6A14V alloy lattice materials by SLM technology restrict its further application.In order to solve the above problems,relevant studies were carried out in this paper.First,take the F2CCZ structure(face-centered cubic structure with vertical struts)as the research object,and the mechanical properties of Ti6A14V alloy lattice materials formed by SLM technology with different aspect ratios were investigated by combining numerical analysis and experimental research.Then the structure of F2CCZ was optimized according to the load environment,which laid a foundation for the design of low density and high strength lattice structure.Finally,different post-treatment methods were used to regulate the microstructure and surface state.The main results are as follows:(1)Using beam element analysis method,the mechanical properties of F2CCZ structure under external loading condition are analyzed,and the constitutive relationship between length-diameter ratio of bars and elastic modulus and yield strength is established.(2)It is established that the pillar diameter of the lattice material formed by SLM technology is the primary factor of error source between SLM and the design model.Secondly,when the pillar diameter is constant,the size error will increase with the decrease of the aspect ratio.(3)The compressive strength and tensile strength of lattice materials increase with the decrease of aspect ratio.Compared with the original structure,the compressive strength of the optimized structure increases by 295.81%,while the density only increases by 79.21%.(4)The microstructure of the lattice material formed by SLM technique is composed of acicular α’ martensite with high density dislocation,and the contribution of high density dislocation to the strength is up to 29.73%.After double solution and aging treatment,the microstructure changes from needle-like α’martensite(width<1μm)to α+β lamellar structure,and there are a laths(width:400 nm-10μm)and β nanoparticles,which can simultaneously improve the strength and toughness of the lattice material.(5)The dual surface modification technology of pre-chemical polishing and micro-arc oxidation can remove the adhering powder on the surface of the lattice material and improve the ductility while ensuring its load-bearing capacity.The specific strength of the sample after pre-chemical polishing and micro-arc oxidation treatment for 5 minutes is even higher than that of the untreated sample,reaching 134.65 MPa/(g/cm~3).