Study On Microstructure And Properties Of Titanium Matrix Composites Fabricated By Additive Manufacting

The particle reinforced titanium matrix composites were fabricated by laser cladding deposition technology.TC4 titanium alloy was used as matrix and TiB as reinforcement phase.The phase composition and microstructure of titanium matrix composites fabricated by additive were analyzed by metallographic microscope,scanning electron microscope,X-ray diffractometer and energy dispersive spectrometer.The tensile test was carried out by universal testing machine,and the mechanical properties of the composites were analyzed based on the tensile test results.The results show that TC4 titanium alloy composites are deposited by laser cladding with TiB as the reinforcing phase.It is found that the composite is composed of ?-Ti,?-Ti and TiB by XRD test and energy spectrum analysis and EBSD analysis.The matrix of the composite is TC4 titanium alloy,which has the characteristics of net basket.With the increase of TiB content,the length of the ? lamellae becomes shorter and the grain refinement becomes shorter.It can also be found that with the increase of TiB content,the distribution of TiB is more uniform and the grain refinement degree increases.The grain size of TiB decreased from 1294 ? m to 28.6 ? m with the increase of TiB content from 0 to 1%.The results show that TC4 titanium alloy composites are deposited by laser cladding with TiB as the reinforcing phase.It is found that the composite is composed of ?-Ti,?-Ti and TiB by XRD test and energy spectrum analysis and EBSD analysis.The matrix of the composite is TC4 titanium alloy,which has the characteristics of net basket.With the increase of TiB content,the length of the ? lamellae becomes shorter and the grain refinement becomes shorter.It can also be found that with the increase of TiB content,the distribution of TiB is more uniform and the grain refinement degree increases.The grain size of TiB decreased from 1294 ? m to 28.6 ? m with the increase of TiB content from 0 to 1%.After solution treatment,the microstructure of the composite can be found obviously.With the increase of solution temperature,the microstructure gets coarsening obviously.The ? phase gradually changes from strip to sheet,and the microstructure of the composite finally becomes sheet ? phase,basket ? phase and ? phase.Through the analysis of tensile test,it can be found that with the increase of TiB content,the strength of the composite increases obviously and the plasticity decreases.The increase of strength is because TiB refines the grain of the composite and produces fine grain strengthening effect.Meanwhile,during the deformation process of the composite,TiB will play the role of load transfer strengthening and bear the load transferred from the surrounding grains,so that the strength of the composite is improved.In the process of deformation,the aurovian strengthening mechanism is produced in TiB,and the dislocations generated in the process of deformation will leave dislocation loops near TiB when they encounter TiB,which will consume energy and make the composite can bear more load.At the same time,it is found that the angle between TiB growth direction and stress direction also has an effect on the strengthening effect.When the angle between TiB growth direction and stress direction is 0-45°,TiB has the strengthening effect.When the angle between TiB growth direction and stress direction is 45-90 °,because of the difference of elastic modulus between TiB and TC4,it is easy to produce cracks between TiB and TC4 matrix,so the TiB growth direction is different from stress direction When the angle of force direction is between 45 ° and 90 °,TiB may be used as the crack source to produce cracks,leading to fracture failure of the composite.It is found that with the increase of TiB content,the fracture mechanism changes from ductile fracture to brittle fracture.When the TiB content is 0.5%,the mechanical properties of the composite are the best.After solid solution heat treatment,the strength of the composite increases,and the elongation after fracture is related to the boron content.When the boron content is less than0.5%(wt),the shrinkage after fracture shows a downward trend;when the boron content is greater than or equal to 0.5%(wt),the shrinkage after fracture shows an upward trend.The strength of the composite material after solution treatment does not decrease significantly,and the elongation after fracture is greatly improved compared with the sample without solution treatment.The composite material with a B content of 1%(wt)without solution treatment is after fracture The elongation rate is 3.5%,and the post-break elongation rate of the composite material after solution treatment at 980 ?is 21%,which is greatly improved compared with the previous one.