| Selective Laser Melting(SLM),as one of the most promising additive manufacturing technologies,uses a high-energy laser beam to scan the pre-coated metal powder layer by layer according to the preset scanning path,the metal powder is completely melted,cooled and solidified to form the sample.This technology has the advantages of forming any complex part,high material utilization rate,and short molding cycle.Ti6A14V(TC4)alloy is an ?+?two-phase alloy,which has wide application prospects in the aerospace,nautical and biomedical fields due to its characteristics,such as low density,light weight,high specific strength,good biocompatibility and corrosion resistance and so on.Using the SLM process is expected to obtain titanium alloy parts with fine structure,uniform composition and no segregation,and excellent performance.In this paper,the Ti6Al4V alloy is used as the raw material.Firstly,the anisotropy of the microstructure and properties of the Ti6A14V alloy produced by SLM is discussed.Secondly,the influence of the addition of Nb on the microstructure and properties of the Ti6A14V alloy sample is explored.Finally,the effect of annealing temperature on the microstructure and properties of alloy sample is studied.Exploring the most effective forming process and annealing temperature to enhance the performance of the sample,in order to prepare titanium alloy parts with high plasticity and high corrosion resistance,and strengthen its scope of use and utilization rate in engineering,the main conclusions are as follows:(1)The effect of different build orientations on the mechanical properties and corrosion resistance of Ti6A14V alloy produced by SLM are studied,and the samples show obvious anisotropy.The results of the compressive tests show that the compressive strength and yield strength of different samples is not much different,but the plasticity is greatly different,the sample with building direction of 0° has the best plasticity,the sample with building direction of 90° is the second,and the sample with building direction of 45° has the worst plasticity.This is because the specimens with different build orientations have different slip surfaces during compression.The microhardness test shows that the sample with building direction of 45° has the highest hardness due to the large amount of hard phase acicular martensite a' and low density.In addition,in terms of corrosion resistance,for the cross section,the corrosion resistance of the sample with building direction of 90° is the best;for the longitudinal section,the sample with building direction of 0° has the best corrosion resistance.(2)The effect of different forming process parameters on the forming quality,mechanical properties and corrosion resistance of Ti6A14V+5Nb alloy are discussed.It was found that when the laser power is 345 W,the scanning speed is 950 mm/s,the scanning spacing is 0.12 mm,and layer thickness is 0.03 mm,the densest sample can be obtained,and excellent mechanical and corrosion resistance can also be obtained.Due to the addition of the Nb element,columnar? grains and cell ? grains of ultrafine structure can be observed in the microstructure of the Ti6A14V+5Nb alloy,and the volume fraction of the ? phase increases significantly.Compared with the Ti6A14V alloy matrix,the plasticity of the Ti6Al4V+5Nb alloy has been significantly improved,the compressive strength has been slightly improved,the yield strength has been reduced,and the corrosion resistance of the alloy has also been enhanced.(3)The effect of different annealing temperatures on the microstructure,mechanical properties,and corrosion resistance of Ti6Al4V alloy samples produced by SLM are studied.After treatment at different annealing temperatures,the acicular martensite ?' phase is decomposed,showing a lamellar ?+? mixed structure,and the volume fraction of ? phase increases with the increase of the annealing temperature.The compression test showed that the yield strength of the sample increased with the increase of the annealing temperature.In addition,after heating and holding at 730 0C,the sample showed the best plasticity without significant reduction in compressive strength.After heating and holding at 1015?,the compressive strength and plasticity of the sample is poor,due to the formation of Widmanstaten structure.The annealed sample is dominated by the grain size,the corrosion resistance decreases with increasing grain size,the samples annealed at 730? show best corrosion resistance,and the samples annealed at 1015? show the worst corrosion resistance. |
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