Microstructure and mechanical properties of large Ti6Al4V components by electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF)-built Ti–6Al–4V(Ti6Al4V) has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. Large components prepared by additive manufacturing (AM) have heterogeneous microstructures, defect size, and residual stress in the building direction due to the high temperature gradient. The samples with a height of 170 mm ware prepare via EB-PBF. The microstructure, mechanical properties, defect size, and residual stress along the building direction have been systematically study in this work. The grains epitaxial growth along the build direction as coarse prior β columnar grains. The residual compressive stress increases from the sample bottom to top. The max void size increases from 23.8 μm at the bottom to 108 μm at the top, and the mechanical properties gradually deteriorate along the building direction, which is related to the temperature gradient on the building direction of the sample. It is found that the ultimate tensile strength decreases from 916 ± 9 MPa at the bottom to 876 ± 7 MPa at the top, and the elongation to failure decreases from 9.13 ± 0.61 % to 6.49 ± 0.34 %. Meanwhile, the hardening ability is also weakened along the building direction. This study reveals the evolution process of the sample's microstructure, mechanical properties, and defects, providing data support for further control of material defects.