One of the issues that modern implants face is their high stiffness, coupled with a positive Poisson’s ratio along the implant. This creates certain problems with bone inflammation and implant detachment. A possible solution to these problems is TiNi alloy lattice structure implants with low stiffness and negative Poisson’s ratio. This paper presents the results of simulation, fabrication by the SLM technique, and study of lattice structures with negative Poisson’s ratio, which can help to solve said problems. The studies involve the determination of mechanical characteristics, Poisson’s ratio, transformation temperatures, and the potential for a superelasticity effect of the lattice structure. The characteristics obtained at initial simulation were partially confirmed in the course of the works. Moreover, the possibility of fabricating TiNi alloy lattice structures with negative Poisson’s ratio (about −0.00323) and low Young’s modulus values (0.818 GPa) was confirmed by the SLM technique.

Spheroidization of Fe and steel powders in a plasma stream of an DC arc plasma torch is investigated. The possibility of obtaining a product with a spherical particle content of up to 100% is established. The fluidity of the best samples of obtained powder is 13–20 s with a fluidity of the feedstock of 39 s. The bulk density of the initial powder (3.05 g/cm³) during the plasma treatment increases to 4.1–4.4 g/cm³. The nanofraction content in spheroidized powders varied from 0 to 75 wt % and it depends mainly on the enthalpy of the plasma stream, consumption of raw materials, and the organization of the flow of the plasma-forming gas in the discharge channel of the plasma torch. It is established that Fe powders spheroidized in plasma can be used in selective laser melting technology to obtain compact samples whose density reaches 7.86 g/cm³.

Three-dimensional printed nitinol (NiTi) alloys have broad prospects for application in medicine due to their unique mechanical properties (shape memory effect and superplasticity) and the possibilities of additive technologies. However, in addition to mechanical properties, specific physicochemical characteristics of the surface are necessary for successful medical applications. In this work, a comparative study of additively manufactured (AM) NiTi samples etched in H₂SO₄/H₂O₂, HCl/H₂SO_4, and NH₄OH/H₂O₂ mixtures was performed. The morphology, topography, wettability, free surface energy, and chemical composition of the surface were studied in detail. It was found that etching in H₂SO₄/H₂O₂ practically does not change the surface morphology, while HCl/H₂SO₄ treatment leads to the formation of a developed morphology and topography. In addition, exposure of nitinol to H₂SO₄/H₂O₂ and HCl/H₂SO₄ contaminated its surface with sulfur and made the surface wettability unstable in air. Etching in NH₄OH/H₂O₂ results in surface cracking and formation of flat plates (10–20 microns) due to the dissolution of titanium, but clearly increases the hydrophilicity of the surface (values of water contact angles are 32–58°). The etch duration (30 min or 120 min) significantly affects the morphology, topography, wettability and free surface energy for the HCl/H₂SO₄ and NH₄OH/H₂O₂ etched samples, but has almost no effect on surface composition.

This study examines the Inconel 718/Ti6Al4V multi-material with a Cu and Nb interlayer produced by SLM. To achieve this, it is necessary to investigate the microstructure, the chemical and phase composition, and the hardness of the interfacial zone in the multi-material samples. Furthermore, it is necessary to determine the impact of interlayer utilization on the mechanical properties of multi-material samples. The investigation showed that the formation of island macro-segregation was observed in all interfacial zones of the multi-material samples. The interfacial zones, Ti6Al4V/Nb and Cu/Inconel 718, exhibited a relatively sharp transition in the chemical composition. In contrast, the Cu/Nb interfacial zone exhibited a gradual transition. The results of the chemical composition study indicated that the width of the Nb/Cu transition zone was approximately 700 μm. No new phases were identified in the production of the multi-material samples. The typical phases were present in the alloy zone, as well as in the Nb/Cu interfacial zone. During the transition from the Ti6Al4V zone to the Inconel 718 zone through the Nb and Cu zones, the average microhardness values changed as follows: 270 → 190 → 120 → 300 HV. The ultimate tensile strength values for the multi-material samples reached 910 MPa.

Multi-material can have functional properties, which are not typical for the materials of which they are composed (for instance, shape-changing effect). This can be used in robotics, micromachines, aerospace, and other fields. In this work, the 316L/FeNi36 multi-material produced by selective laser melting was investigated. The results show that the interfacial zone of the multi-material exhibits mixing regions of the two alloys but no defects. The microstructure is constituted by large grains with epitaxial growth, which propagate in a directional manner from the 316L alloy through the interfacial zone to the FeNi36 region. The multi-material sample displays three different zones of chemical composition: the FeNi36 composition zone; the interfacial zone; and the 316L zone. The size of the interfacial zone is approximately 50 µm. The multi-material sample exhibits the presence of three distinct phases: γ-Fe; γ-Fe64Ni36; and α-Fe. The hardness of the FeNi36 zone is approximately 163 HV, followed by an interfacial zone with a hardness of approximately 200 HV and then, the 316L zone with a hardness of approximately 214 HV. Functional tests demonstrate that the shape-changing effect is directly correlated with the variation in the FeNi36 thermal expansion coefficient with temperature. For achieving the most pronounced shape-changing effect, the temperature range of 25–215 °C is more suitable.