Mechanical and microstructural characterization of Ti6Al4V lattice structures with and without solid shell manufactured via electron beam powder bed fusion

The topological optimization of components by means of lattice structures allows to reduce their weight avoiding a loss in the mechanical performance. Often the lattice parts are integrated in a more complex geometry, and they present an interface with a solid part. In the present paper, the mechanical and microstructural characterization of Ti6Al4V lattice structures with body-centered cubic unit cell was carried out. Samples with and without an external solid shell were designed and produced with electron beam powder bed fusion in order to investigate the behavior of these complex structures, especially at the interface between the solid and lattice parts. The microstructure and defects were analyzed, and compression tests were performed on the samples with and without solid shell to understand the influence of the solid part and its interaction with the lattice structure. After the fracture and detachment of the shell, the same behavior for both set of samples was observed. Finally, a finite element model was defined to better understand the mechanical behavior of the investigated structures. The nominal sample stiffness was significantly higher than the experimental one. This discrepancy can be attributed to local defects, both in terms of porosities and deviations from ideal geometry.