The mechanical strength of Ti-6Al-4V columns with regular octet microstructure manufactured by electron beam melting

Columns with regular octet lattice microstructure have been manufactured by electron beam melting of Ti-6Al-4V powders. Each column comprised sixteen cells in the axial direction and three cells in the transverse direction and was manufactured in four different nominal slenderness for the struts. The columns were destructively tested both in tension and in compression, and both their macroscopic stiffness and strength were measured. The experimental results showed large discrepancies from the numerical and analytical predictions, which were explained on the base the imperfections observed in the solid material of the lattices. A model for the random generation of defects, based on the peculiarities of the electron beam melting process has been devised and used to generate defects whose statistical distribution matched the one observed in the test articles. A finite element model, including the automatically generated defects, showed to produce satisfactory agreement with the experimental results, and allowed to quantify the impact of typical imperfections occurring in additive manufacturing processes on the mechanical properties of parts with fine lattice microarchitecture.