Magnesium Alloy Biomaterials: Innovative Engineering Solutions for Future Biodegradable Implant Materials

Magnesium (Mg) alloys are promising candidates for temporary orthopaedic and cardiovascular implants due to their biocompatibility, mechanical compatibility with bone, and complete biodegradability in the human body. Although extensive research has focused on alloying and conventional heat treatments to tailor their performance, the application of deep cryogenic treatment (DCT) remains largely unexplored. DCT, which involves exposure to cryogenic temperatures, has been shown to enhance hardness, wear resistance, and corrosion behaviour in various steels and alloys. However, its use in biomedical systems is still at an early stage. In this study, the influence of DCT on the microstructure, mechanical properties, and corrosion behaviour of Mg-Gd alloys with different Gd contents was systematically investigated. Three compositions Mg-2Gd, Mg-5Gd, and Mg-10Gd were examined under conventionally extruded (CHT) and DCT (−196 °C) for 8 h, 24 h and 48 h states. Microstructural and phase characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and atom probe tomography (APT). Additionally, XRD-based micro-residual stresses were analysed to observe changes in the stress state of the material in response to specific treatment procedure. Next, corrosion behaviour was evaluated by potentiodynamic polarization, while Raman shift spectroscopy was used to analyse surface oxides and passivation layer formation. Mechanical response was assessed via Vickers microhardness testing. The results demonstrate a clear compositiondependent response to DCT. A significant increase in hardness was observed for Mg-5Gd, whereas Mg-2Gd and Mg-10Gd exhibited reduced hardness following treatment. Changes in corrosion behaviour were also observed for all three alloys after DCT, suggesting that cryogenic processing alters the electrochemical response of the materials, likely through modifications of the microstructure. However, the mechanisms governing these corrosion changes remain not yet fully understood and warrant further investigation. These findings highlight the potential of DCT as a supplementary processing route for tailoring the performance of biodegradable Mg-Gd alloys for biomedical applications.