[T6] AM Beam Based Technologies

[15B-T6-27] Additive Manufacturing of Anisotropic Ti-6Al-4V Cubic Hollow-Strut Lattice Structures with High Specific Yield Strength: Optimization, Properties and Failure Modes

H. Tang¹, *S. Xu¹, C. Ding¹, M. Huang¹, X. Yang¹ (1.Hangzhou City University, China)

Keywords:Additive manufacturing, TC4, Cubic lattice structure, Hollow strut, Gibson-Ashby model

Additive manufacturing enables the design and fabrication of complex lattice structures, thereby realizing their performance potential. The study employed three design strategies to enhance the strength of the basic cubic lattice structure. Firstly, solid struts were replaced with hollow struts. Secondly, the proportion of vertical struts was increased. Lastly, cross-shaped plates were adding into the hollow struts to stabilize the inner-plane of the lattice structure. Compression tests and finite element modeling were conducted to evaluate the compressive properties of lattice structures with different parameters. Furthermore, the study uncovered the failure modes of the lattice structures at varying relative densities and vertical material proportions. The results demonstrate that substituting solid struts with hollow ones, the compressive yield strength of lattice structures increases by 109%. Increasing the vertical material proportion from 70% to 85%, at a relative density of 0.25, leads to a significant increase in yield and ultimate strength, surpassing 19% to 278.7 MPa and 377.5 MPa, respectively. Additionally, by adding cross-shaped plates inside the hollow struts at a vertical material proportion of 90%, the specific yield strength of the lattice structure can reach up to 250 MPa·cm³/g, which is significantly higher than the matrix material. The optimized anisotropic lattice structures exhibited exceptional uniaxial strength, tremendously surpassing the predicted limits of the Gibson-Ashby model. To incorporate the anisotropy of these lattice structures, a modification was made to the Gibson-Ashby model by introducing the vertical material proportion α. Besides, by increasing the relative density and incorporating cross-shaped plates inside the hollow struts, the fracture mode shifted from out-of-plane buckling of thin walls to fracture along the 45^o plane. These discoveries are expected to provide both experimental data and a scientific foundation for designing anisotropic lattice structures with remarkably high specific strength.