Study On The Processing Parameters And Properties Of Ti6Al4V And Its Porous Structures Fabricated By Selective Laser Melting

After the wrought artificial replacement joint being implanted into the human body,due to some problems such as mechanics and biocompatibility,it usually causes defects in the surrounding bone.Therefore,it is necessary to use other methods to manufacture the implant so that it can make up for the defect and also have good compatibility.As porous structures,the implant’s pore size,porosity and elastic modulus determine the efficacy of fusion and whether or not avoiding the “stress shielding”.Selective Laser Melting is a universal metal 3D printing technology with good shaping accuracy.The porous implants that have interconnected and regular cell pores cannot be achievable by traditional processing methods but can be rapidly fabricated using Selective Laser Melting technology.The purpose of this thesis is to study the process characteristics and mechanical properties of the SLM Ti6Al4 V bulks and porous structures,then lay the foundation for the preparation of porous implants that meet the human bone parameters.The main research contents and results are as follows:(1)Optimization of Ti6Al4 V bulk forming parameters and exploration of regularity.The effect of laser power,scanning speed,and scanning distance on the relative density of molding was studied and the optimum forming process was P=280W,V=1200mm/s,S=0.1mm.On the other hand,the surface roughness was also studied by adjusting different parameters.(2)Optimization of the heat treatment process.Using the optimal parameters to shape the specimen,explore and obtain the best heat treatment process(900oC for 30 min,furnace cooling).The sample has a tensile strength of 945 MPa and an elongation of 18%.After hot isostatic pressing,the strength and elongation rate were increased to 989 MPa and 20% respectively.(3)The samples fabricated in the 45 degree forming direction has the biggest tensile strength 1278 MPa.In addition,study on the influence factors of mechanical properties.The tensile strength(1228 MPa)and elongation(6.67%)obtained by the strips scanning strategy are larger than the chess scanning strategy.The impact toughness is 21.4J/cm2 for the horizontal direction forming sample.(4)Research on forming process and mechanical properties of porous structures.Laser parameters have an influence on the grid geometry,porosity and mechanical properties of the porous structure.The compression failure mechanism of porous structure is adiabatic shearing.The compression process includes three stages of elastic deformation,plastic collapse and densification.