Research On Mechanical Behavior Of High Strength And High Toughness Titanium Alloy Fabricated Using Laser Deposition Manufacturing

The rapid development of aviation industry puts forward higher requirements for materials.In order to meet the production requirements,the research of high-performance titanium alloy is of great significance.A new type of Ti-6Al-2Mo-2Sn-2Zr-2Cr-2V titanium alloy with high strength and high toughness was prepared on the basis of Ti-6Al-4V titanium alloy,which is widely used.The microstructure and force of the alloy were analyzed by optical microscope,scanning electron microscope,microhardness tester,tensile,impact and fatigue tests were studied.It provided theoretical data support for further exploration of the development of high strength and high toughness titanium alloys.By testing the tensile properties,impact properties and microhardness of the samples at different solution temperatures,the formation and evolution of the alloy structure before and after heat treatment were analyzed;the high cycle fatigue properties after solution aging treatment were compared with Ti-6Al-4V,and the effects of microstructure and structural defects on the mechanical properties were discussed.The results showed that after solution aging in the two-phase region,the microstructure was similar to that as deposited,and it was still composed of coarse columnar crystals,but the ? phase was coarsened and the volume fraction of ? phase was significantly increased;after solution aging above the ?transformation point,the primary ? phase disappeared and a large number of secondary ?phase were precipitated.The tensile strength,impact toughness and microhardness of titanium alloy were improved by solution aging heat treatment,and the impact toughness value in deposition direction was much higher than that in laser scanning direction.Comprehensive analysis showed that the heat treatment system of 920? × 2h,air cooling+540? × 4h air cooling can made the alloy obtain better mechanical properties.Compare with Ti-6Al-4V alloy samples prepared with the same process,the fatigue performance of the alloys is higher in the high-stress zone,but lower in the low-stress zone,the difference in alloy element content,phase composition and microstructure are the main factors that contribute the distinguishing fatigue performance of the two alloys.Fracture analysis showed that most of the nucleation site of the fatigue source were located at the non-fusion defects of the strip and the porosity defects,bigger diameter of the defect and smaller distance to the surface effect the faster the fatigue crack initiation.