Mechanical Performance of Ti-6Al-4V Functionally Graded Lattice Structures Prepared by L-PBF

Linear porosity gradient samples based on the body-centered cubic (BCC) unit cell were designed and fabricated using laser powder bed fusion (L-PBF). This study investigates how the scale and direction of porosity gradients affect the mechanical properties of BCC lattice structures. The results indicate that optimizing the scale and orientation of the porosity gradient can effectively regulate the elastic modulus, yield strength, and energy absorption capacity of lattice structures. Compared to uniform lattice structures, functionally graded lattice structures display a lower elastic modulus and superior mechanical performance when the porosity gradient is oriented perpendicular to the compression direction. In particular, BCC1-V shows an 11.34% increase in elastic modulus, a 24.79% increase in yield strength, and a 37.51% increase in compressive strength compared to BCC1-P. Furthermore, a pronounced porosity gradient aligned with the load direction enhances energy absorption capacity through a sequential fracture mechanism. Both strut diameter and porosity gradient direction play a critical role in fracture characteristics. The porosity gradient model exhibits a combination of bending and tensile deformation behaviors, with fracture surfaces showing a mixed brittle-ductile fracture mechanism. This study provides new insights into the multiscale design of porosity gradient lattice structures, with the goal of optimizing their performance for multifunctional applications.