Parameter optimization and tensile properties of additively manufactured lattice structures of Ti6Al4V alloy

The effects of laser processing parameters on dimensional accuracy, the formation of pores and surface defects, as well as tensile properties of the Ti6Al4V alloy lattice structures prepared by laser powder bed fusion technique were investigated. The lattice structure size and pore defects were characterized by X-ray tomography. The results showed that the size of the lattice structure was strongly affected by the building direction and deviated with the designed values. There existed a linear correlation between the lattice structure size and energy density. The optimal parameters for minimizing porosity were 250W and 1000 mm/s for the face-centered cubic with Z-struts (FCCZ) lattice structure (0.0064 %) and 250W and 1200 mm/s for the Diamond lattice structure (0.0070 %). Tensile specimens were printed accordingly, and the ultimate tensile strength values were 140.71 MPa, 120.59 MPa and 106.05 MPa for the FCCZ, hollow simple cubic (HSC) and diamond lattice structures, respectively. The FCCZ failed at nodes parallel to the tensile direction. The HSC failed at the connection between vertical and horizontal plates. The Diamond failed at regions parallel to the tensile direction. The simulation based on the Gurson-Tvergaard-Needleman (GTN) model with porosity considered agreed well with experiments, and could predict the damage evolution behavior and final fracture location.