Superior energy absorption of continuously graded microlattices by electron beam additive manufacturing

Electron beam melted (EBM) Ti-6Al-4V functionally graded materials (FGM) with continuously graded densities are investigated for dimensional accuracy, compressive properties, fractography and build direction effect in comparison to uniform density counterparts of the same volume. It is found that FGMs exhibit progressive layer-by-layer deformation mode regardless of unit cell designs and build direction. This deformation behavior is highly favourable for uni-directional impact absorption applications compared to uniform density counterparts with random or diagonal failure. Overall, the EBM-built FGM exhibits superior energy absorption than counterparts of uniform density. Significant improvement in the quasi-elastic gradient and energy absorption is obtained by changing the build direction for specific designs. Compared with other FGM or uniform density lattice structures from the literature, the energy absorption of lattice structures with lower relative density could outperform those with higher relative density by changing the unit cell design or density profile.