Direct ink writing of porous Fe–Ti6Al4V and Fe-Inconel 718 bimetallic structures

Additive manufactured bimetallic structures provide site-specific functions by joining two metallic materials in the designed area, offering customized solutions for biomedical and engineering applications. However, cracking, delamination, or cross-contamination frequently occurs at the joint between two dissimilar metallic materials due to their different thermal properties. In the paper, porous bimetallic structures made of biomedical materials (Fe, Ti6Al4V, and Inconel 718) for bone implants are fabricated via direct ink writing (DIW) with a dual syringe system. After subsequent heat treatment, the original shapes of the bimetallic structures are well-preserved, and the shrinkages of the two materials are equalized by adjusting the sintering temperature. All joints are free of cracks and delamination, and the material deposition sequence has no impact on them, according to microstructural analyses of the interface. The pores created by binder pyrolysis and metallic powder sintering are necessary for bone growth, cell migration, body fluid flow, etc. The Fe–Ti6Al4V and Fe-Inconel 718 bimetallic structures have better mechanical properties than the Fe structures and can perform multiple functions that are challenging for monometallic implants.