The metastable β-Ti21S alloy exhibits a lower elastic modulus than Ti-6Al-4V ELI while maintaining high mechanical strength and ductility. To address stress shielding, this study explores the integration of lattice structures within prosthetics, which is made possible through additive manufacturing. Continuous adhesion between the implant and bone is essential; therefore, auxetic bow-tie structures with a negative Poisson’s ratio are proposed for regions under tensile stress, while Triply Periodic Minimal Surface (TPMS) structures with a positive Poisson’s ratio are recommended for areas under compressive stress. This research examines the manufacturability and quasi-static mechanical behaviour of two auxetic bow-tie (AUX 2.5 and AUX 3.5) and two TPMS structures (TPMS 2.5 and TPMS 1.5) in β-Ti21S alloy produced via laser powder bed fusion. Micro-CT reveals printability issues in TPMS 1.5, affecting pore size and reducing fatigue resistance compared to TPMS 2.5. AUX 3.5’s low stiffness matches cancellous bone but shows insufficient yield strength and fatigue resistance for femoral implants. Biological tests confirm non-toxicity and enhanced cell activity in β-Ti21S structures. The study concludes that the β-Ti21S alloy, especially with TPMS 2.5 structures, demonstrates promising mechanical and biological properties for femoral implants. However, challenges like poor printability in TPMS 1.5 are acknowledged and should be addressed in future research.

Refractory high entropy alloys have shown potential to be developed as structural materials for elevated temperature applications. In the present research, the multielement alloy Fe2TiVZrW0.5 was produced by high-energy ball milling of elemental powders in the air to promote the formation of reinforcing oxide and nitride particles followed by spark plasma sintering consolidation. The sintering temperature was optimized to achieve a full-density material that was characterized from the microstructural and mechanical points of view. Hardness and KIC were measured in the as-sintered condition as well as after thermal treatment at 1100 °C. TEM observations showed the presence of a fine distribution of ZrO₂ and Ti(V)-N in the microstructure mainly constituted by the bcc Fe-V and Fe-V-W phases. The fine distribution of ceramic particles in a metallic multielement matrix is responsible for the consistent hardness and thermal stability of this alloy.

Cobalt is the most used metal binder in hard metals since its extraordinary wetting, adhesion and mechanical properties. Nevertheless, it has been recognized genotoxic and cancerogenic with higher toxicity in combination with WC. To substitute Co with an alternative binder, the interaction between the binder and WC must be taken into account. In this work, IN625 is considered as a binder alternative due to its desirable combination of high-temperature strength and corrosion/oxidation resistance. A characterization of the interaction between WC and IN625 was carried out by means of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS) and X-Ray Diffraction (XRD). Depending on the sintering temperatures, different phases were evidenced at the WC–IN625 superalloy interface. From 1250 °C to 1300 °C, where solid-state sintering takes place, (Cr,Mo)₂₃C₆, W₂C and (Cr,W) solid solutions were detected. At a sintering temperature of 1350 °C, IN625 melts and the formation of additional phases, such as an intermetallic Ni₄W phase and (Mo,W) and (Mo,Nb) solid solutions, were observed. The precipitation of NbC and (Mo,Cr)₂₃C₆ carbides in IN625 was also detected.