Abstract: The size effect of Ti-6Al-4V submillimeter structures manufactured by selective laser melting, which is critical for metallic mechanical metamaterials of unique mechanical properties, for example, negative Poisson's ratio and ultrahigh modulus, which show promise in biomedical, environmental, energy-related applications, has not been systematically investigated. Presented here are the quantification of the porosities by X-ray microtomography scans, texture analysis, and mechanical characterization of the additively manufactured Ti-6Al-4V microbeams. We found linearly decreasing porosities, increasing mechanical properties, and increasing texture in the microbeam with increasing diameter from 250 to 500 µm. The variation of microstructure in microbeams of different diameters and along the sample height, resulting from the printing parameters and the thermal conditions, leads to the discrepancy between the behavior observed in experiments and finite element simulation. Our results provide the structure-property-processing correlation to improve the manufacturing and prediction of the mechanical behavior of metallic mechanical metamaterials.

Key words: Selected laser melting, Porosity, Texture, Epitaxial growth, Finite element modeling, Metallic mechanical metamaterials