Evaluation of mechanical properties of Ti-6Al-4V BCC lattice structure with different density gradient variations prepared by L-PBF

Based on the optimized pore size distribution and relative density, the functionally graded lattice structure is capable of achieving better mechanical properties than a uniform lattice structure with similar porosity. In this study, in order to investigate the effect of the strategy of density gradient variation on the lattice structure with similar porosity, three different density gradients were designed for the BCC-based lattice structure in parallel and perpendicular to the loading direction based on Ti-6Al-4V alloy powder and laser beam powder bed fusion technology, respectively. The results showed that the elastic modulus, yield strength and compressive strength of the lattice structure with a density varying as a logarithmic function perpendicular to the loading direction were 39.91%, 51.85% and 51.72% higher than the uniform lattice structure respectively. Moreover, the layer-by-layer collapse phenomenon was the primary aspect impacting the energy absorption in the lattice structures with density gradient parallel to the loading direction. By observing the fracture morphology of the lattice structures, it was found that all specimens exhibited dimple and smooth plane morphological features for a mixed failure mechanism of cleavage and dimple rupture, indicating that the failure mode of the lattice structures are a combination of brittle and ductile deformation. Therefore, a reasonable density gradient design can significantly improve the mechanical properties of the lattice structure with similar porosity. This work provides valuable inspiration for the design of lattice structures in engineering applications.