Microstructure And Mechanical Properties Of Ti-6Al-4V Alloy Fabricated By Electron Beam Additive Manufacturing

Electron Beam Melting(EBM)technology has the advantages of high energy utilization and absorption rate.It is one of the rapid and high-quality forming technologies for complex titanium components in the field of biomedicine.In this work,EBM was used to prepared Ti-6Al-4V alloy implants with complex arcs and accurate screw location.Morphology,defects,microstructure and mechanical properties of the implants were analyzed.The influence of electron beam current on microstructure and mechanical properties were systematically studied,providing process theoretical basis for high-quality preparation for the implant plate.The effects of electron beam current on the morphology,metallurgical defects and density of the implanted plate were investigated.Pits can be observed in the maximum curvature of the implanted plate under 10 m A and molten particles are easy to be adhered to the surface under 20 m A.However,when the beam current is 15 m A,quality of the surface is the best.Industrial CT results show that the defects are irregularly spherical or strip-shaped,the average defect volume is 0.01 mm3,and the maximum volume is 1.10 mm3.The microscopic defects are stoma,and the large-size defects are interlayer gaps,the density of the implanted plateis largerthan 99.98%.The effects of electron beam current and height of the implanted plate on composition and density of the implanted plate were studied.The results show that different electron beam currents and different height alloys of implanted plates have stable chemical composition and consistent density;The Al element has no obvious burn damage,the density of the implanted plate is about 4.42 g/cm3,and the relative density is about 99.33%.The effects of electronbeam current and height of the implanted plate on phase constitution,α plate size and orientation,mechanical properties of Ti-6Al-4V alloy were investigated.The results show that microstructure of the alloy is lath-like a phase and needle-like α’ phase.Very fine α and α’ phases are di stributed in the coarse β columnar crystals.The residual βphase mainly exists in the gaps of a slats.With the beam current increases,the a phase changes from a long strip to a rod shape.The spacing of a slats is slightly reduced,while the size of the α slats is slightly increased.The a slats are dominated by high-angle grain boundaries,and the proportion of small-angle grain boundaries decreases with increasing beam current.When the electron beam current is 15 mA,the average spacing of a slats is 1 pm and the average size is 19 μm.As the height increases,the a phase in the<0001>1<1010>direction decreases.The mechanical properties of the implant plate are Rm≥928 MPa、Rp0.2≥874 MPa、A≥12%,Et≤13 GPa,Rmc≥671 MPa and HV 20≥320.The fracture is dominated by dimples,and the fracture form is ductile-brittle mixed fracture fracture.The mechanical properties of the implant plate meet the requirements of surgical implants.