Functionally graded scaffold (FGS) is designed to mimic the morphology, mechanical and biological properties of natural bone closely. Porosity variation strategy between different regions in FGS plays a crucial role in influencing its mechanical and biological performance. A combination of modeling tool and scripting language can effectively enhance the ability to optimize FGS designs. This study was aimed at determining the effect of porosity variation strategy on the mechanical performance and permeability of the as-built and as-heat-treated FGSs. Ti-6Al-4V FGSs with sizes of 10×10×15 mm and diamond lattice structures were designed and fabricated by means of selective laser melting. A wide range of porosities in the FGSs (38~75%) were achieved by applying six different porosity variation strategies. The elastic modulus (3.7~5.7 GPa) and yield strength (27.1~84.7 MPa) of the as-built FGSs were found to vary between the corresponding mechanical properties of cancellous bone and cortical bone. Heat treatment reduced the strengths by 13~56%. Porosity variation strategy strongly affected the deformation behavior and failure mechanisms of the FGSs. The sigmoid function-controlled FGSs showed gradual failure behavior and

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Laser powder bed fusion (LPBF) is being increasingly used in the fabrication of complex-shaped structure parts with high precision. It is easy to form martensitic microstructure in Ti-6Al-4V alloy during manufacturing. Pre-heating the powder bed can enhance the thermal field produced by cyclic laser heating during LPBF, which can tailor the microstructure and further improve the mechanical properties. In the present study, all the Ti-6Al-4V alloy samples manufactured by LPBF at different powder bed temperatures exhibit a near-full densification state, with the densification ratio of above 99.4%. When the powder bed temperature is lower than 400 °C, the specimens are composed of a single α′ martensite. As the temperature elevates to higher than 400 °C, the α and β phase precipitate at the α′ martensite boundaries by the diffusion and redistribution of V element. In addition, the α/α′ lath coarsening is presented with the increasing powder bed temperature. The specimens manufactured at the temperature lower than 400 °C exhibit high strength but bad ductility. Moreover, the ultimate tensile strength and yield strength reduce slightly, whereas the ductility is improved dramatically with the increasing temperature, when it is higher than 400 °C.

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Ti-Ta alloys have been widely studied for biomedical applications due to their high biocompatibility and corrosion resistance. In this work, nearly fully dense and in situ alloyed Ti-50 wt% Ta samples were fabricated by the laser powder bed fusion (LPBF) of mechanically mixed powders. With increased exposure time, and thereby increased laser energy density, insoluble Ta particles were almost dissolved, and a Ti-50 wt% Ta alloy was formed. Cellular and dendritic structures were formed due to constitutional undercooling, which was caused by the high cooling rate of LPBF process. Both retained β phases and α″ phases were observed in the LPBFed Ti-50 wt% Ta alloy. The α″ phase was found at the boundary of the cellular structures, where the tantalum content was not high enough to suppress the bcc lattice transition completely but could suppress the β phase → α′ phase transition.

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