To build a suitable corrosion environment for testing the degradation behavior of magnesium alloy in vitro, the medium and test environment are constantly optimized. However, the applicability of medium renewal mode is still vague. In this study, based on three representative test protocols, the influence of the specific ratio of media volume to surface area and the disposable medium real-time renewal mode (flow-through) on Mg corrosion were investigated. It is found that in flow-through medium renewal mode, the composition of the medium is maintained quasi-constant which is essential for corrosion tests. The selection suggestion on medium renewal mode was also proposed. This work is beneficial for ultimately establishing the representative in vitro testing protocols for Mg bioabsorbable materials.

A multimaterial device, composed of Nickel-Titanium (NiTi) and Mg1.2Zn0.5Ca0.5Mn, is developed as a stiffness-matched approach for skeletal reconstruction application. Due to the rapid biodegradation of Mg in the body and the galvanic corrosion occurring due to the interaction of both metals in physiological fluid, we present preliminary results for delaying the degradation of Mg. First a Zn interlayer is introduced between the metals. Second, Mg surface treatment is conducted by via Micro-Arc Oxidation (MAO) and followed by CaP coating. Results shows a characteristic porous surface in the Mg component as result of the MAO treatment. The obtained surface will next work as a perfect surface to receive the CaP coating.

A homogenous microstructure in Mg materials facilitates not only a homogenous degradation but also improved cell adhesion characteristics. Additive manufacturing (AM) technologies like metal injection molding (MIM) and 3D printing use polymeric binders mixed with Mg alloy powders to improve flow and shape characteristics. Analysing the sintered microstructures for suface contaminations becomes important and therefore in this study Raman spectroscopy was utilized to reveal carbonaceous residuals in the MIM Mg-0.6Ca sintered microstructures. EDX analysis predominantly showed oxygen (O), calcium (Ca) and silicon (Si) intensities. Certain precipitates comprised only O intensities whereas Ca and Si intensities coexist at random precipitations in the microstructure. Raman modes observed at nearly 1370 cm-1 and 1560 cm-1 are generally ascribed to the presence of elemental C and the modes observed at 1865 cm-1 are probable C=C stretching. The hydrocarbon cracking during thermal debinding process (400-550 °C) releases C that might interact with Mg to form metastable carbides. The C=C stretching can therefore be related to MgC2 type carbides. Additionally, free C radicals are probable due to accelerated vacuum thermal decomposition of the hydrocarbons in the binder material, which is evident at wavenumbers 1370 cm-1 and 1560 cm-1. Grain interiors are mostly free of any precipitation giving rise to noisy signal in Raman due to the specimen’s metallic nature.The results indicate that Raman is a viable option to characterize carbon impurities on metallic biomaterial surfaces. The exact stoichiometry with respect to Ca and Si elements still needs evaluation, however, the presence of surface C impurities might be important for future cell culture.

Additive manufacturing (AM) offers unique opportunities to meet the complex design requirements of implants such as stents. On the other hand, research on Fe-based biodegradable alloys for stent applications has significantly increased in the last decade due to their suitable mechanical properties such as ductility and high ultimate strength. In this work, the effect of laser powder bed fusion (LPBF) parameters on the corrosion of Fe20Mn0.5C was studied using potentiodynamic polarization and electrochemical impedance spectroscopy. An optimization of LPBF parameters was carried out by varying laser power and scanning speed considering volumetric energy density and sample porosity. Three conditions were selected for electrochemical tests: P160V640, P200V440, and P240V340. The results showed that corrosion resistance is strongly related to porosity, which in turn depends on the volumetric energy density of the LPBF system during the manufacturing process.

This paper concisely reviews the development of a dental implant (DI) manufactured from the novel TiMg bioactive composite material named BIACOM©. BIACOM© enables reduction of the stress-shielding effect and it leads to better biocompatibility compared with that of the traditional Ti and Ti alloys used in dentistry. BIACOM© was fabricated by cold consolidation of atomised TiGr1 and Mg99.8% powder blend. BIACOM© comprises bioabsorbable Mg component in the form of interconnected filaments, elongated along the direction of extrusion, which are embedded within a permanent, bioinert ultrafine-grained Ti matrix. The Ti component provides the mechanical properties, required for a function of the implant during its service. As the Mg content increases, the discrete filaments become interconnected with each other and form a continuous spatial network. The Mg component with low Young`s modulus (E), homogeneously dispersed within the Ti matrix, reduces E of BIACOM©. Moreover, Mg gradually dilutes at a controlled rate from the implant`s surface in contact with a corrosive environment after implantation. As a result, the pores gradually form at prior Mg sites, composite`s E decreases further down, and the stress-shielding phenomenon is reduced. Also, Mg promotes the osseointegration process and a bonding strength increases at the interface between the bone and implant, eventually. In the current paper we report the development of DI, which was manufactured from the optimized BIACOM© composite by an efficient hydro-extrusion consolidation process. The implant was designed in a way to reflect the properties and peculiarities of this novel Ti17Mg composite material. Two different implants designs and two surface finishes were pursued. Static mechanical performance was assessed by the finite element analysis and experimentally verified in compliance with the standard for the fatigue testing of endosseous DI. The corrosion of Mg from the surface of DI was evaluated by H2 evolution volumetric method. In-vitro cytotoxicity biological response was assessed by the indirect contact MTT assay using DMEM extracts of DI and L929 cell line.

The use of biodegradable magnesium alloys in cardiovascular applications supports the "leave nothing behind" strategy, necessitating materials with high tensile strength, elongation, and fine grain sizes. This study investigated the mechanical properties, microstructure, and surface quality of three magnesium alloys (WE43, ZX00, AZ31) subjected to a custom low-profile extrusion process. The alloys were cast, extruded into 9.5 mm billets, and further extruded into wires with diameters of 1.5 - 2.5 mm. Process variables included temperature, speed, method (direct/indirect), and extrusion ratio. Results showed that press speed and temperature are interconnected, with higher speeds raising forming temperatures due to friction and adiabatic heating. Contrary to expectations, press speed alone did not significantly affect outcomes within the tested range. Lower temperatures required higher forming forces, notably in WE43 at 460°C. Surprisingly, higher tensile strengths were achieved with direct pressing despite the higher forming temperatures. For WE43, a tensile strength of 415 MPa was achieved at low temperature and high speed. Recrystallization during forming resulted in finer grain structures, with smaller grains seen in wires with higher deformation degrees. Both tensile strength and elongation varied, with no clear trend linking them; however, higher strengths were sometimes accompanied by higher elongations. The pressing method significantly impacted the mechanical properties, with direct pressing enhancing tensile strength across all alloys. In conclusion, WE43 and ZX00 alloys showed significant process parameter influences on tensile strength. The study suggests that process optimization, especially in press method and temperature control, can enhance the mechanical properties of biodegradable magnesium alloys for cardiovascular applications.

Fe-Mn-C alloys have significant applications in developing temporary implants like bioabsorbable stents. Laser powder bed fusion, a promising additive-manufacturing technique, allows tailoring the microstructure by adjusting laser process parameters, expected to improve the degradation rate and mechanical properties of Fe-Mn alloys. In this study, we produced Fe-16Mn-0.7C bulk samples by varying laser power (50÷70 W) and scanning speed (700÷1000 mm/s), while maintaining a constant volumetric energy density (VED) of 88 J/mm³, to understand the effect of printing parameters on the alloy's performances. Fully austenitic microstructure and mechanical properties (microhardness approximately of 300 HV) appear comparable among the different samples. However, the defect analysis via X-ray micro-computed tomography identified an operational window for producing fully dense Fe-16Mn-0.7C bulk samples using LPBF. This operational window resulted in laser parameters much lower than those reported in the literature. Ongoing corrosion tests are being conducted to validate the obtained results further.