Structural design and mechanical response of gradient porous Ti-6Al-4V fabricated by electron beam additive manufacturing

Abstract

Gradient porous materials are gradually developed for some biomedical implants such as mandible and vertebrae to meet the varied Young's modulus due to serious bone density variation and thus to avoid serious stress shielding effect. In this study, different designs of gradient porous materials are fabricated by additive manufacturing 3D printing via the electron beam melting (EBM) method, and the mechanical properties are examined. The first attempt is to examine the size variation of porosity gradient region, with gradual transition region from 0 to 8 mm in height from the lower 70% porosity region to the higher 90% porosity region. The gradient transition has pronounced impact on the mechanical response improvement of porous EBM foams. The second attempt is to explore the effect of porosity variation and the interface discontinuity degree, or the degree of strut overlapping. The foam mechanical properties are governed mainly by the mechanical properties of the higher porosity portion and the mismatch on the interface; the latter degree of mismatch (or the degree of strut overlapping) plays a more dominant role. By re-designing to fulfill complete continuity with no mismatch of the struts on the interface, significant improvement of the mechanical properties can be achieved.