Magnesium alloys have been extensively studied as degradable biomaterials for clinical applications due to their biocompatibility and mechanical properties. However, their poor corrosion resistance can lead to issues such as osteolysis and the release of gaseous hydrogen. This study investigated the influence of the activation time of magnesium surfaces in a sodium hydroxide (NaOH) solution on the concentration of active hydroxyl groups and corrosion resistance. The results indicated that immersion time significantly influences the formation of a corrosion-resistant film and the distribution of surface hydroxyl groups. Specifically, specimens treated for 7.5 h exhibited the highest concentration of hydroxyl groups and the most uniform oxide film distribution. Electrochemical tests demonstrated capacitive behavior and passive surface formation for all evaluated times, with the 7.5-h immersion in NaOH yielding superior corrosion resistance, lower current density, and a more efficient and thicker protective film. SEM and EDS analyses confirmed increased formation of Mg(OH)₂ for samples treated for 5 and 7.5 h, while a 10-h treatment resulted in a brittle, porous layer prone to degradation. Statistical analysis using ANOVA and Fisher\'s LSD test corroborated these findings. The optimal 7.5-h alkali treatment enhanced magnesium\'s corrosion resistance and surface properties, making it a promising candidate for orthopedic implants. However, further studies are necessary to assess biocompatibility and physiological responses before clinical implementation.

Mg-based and Zn-based biodegradable materials have the potential to become the next-generation implant materials to treat bone diseases, because of their desired degradation and mechanical properties. This article reviews the status of these implant materials. The required properties of biodegradable materials such as biodegradability, mechanical properties, and biocompatibility for performance evaluation were briefly discussed. The influence of fabrication techniques, microstructure, alloying elements, and post-processing techniques on the properties of Mg and Zn-based materials was addressed. The degradation mechanism by dissolution, oxidation, and interaction with human body cells was discussed. The biocompatibility of Mg and Zn-based biodegradable materials was analyzed. The significance of in vitro and in vivo biocompatibility testing was highlighted, emphasizing the superiority of in vivo results over cell line studies. This article identifies the many Mg and Zn-based biodegradable materials and summarizes the key findings.

Magnesium as a biodegradable material offers promising results in recent studies of different maxillo-facial fracture models. To overcome adverse effects caused by the fast corrosion of pure magnesium in fluid surroundings, various alloys, and surface modifications are tested in animal models. In specified cases, magnesium screws already appeared for clinical use in maxillofacial surgery. The present study aims to compare the bone healing outcome in a non-load-bearing fracture scenario of the forehead in sheep when fixed with standard-sized WE43 magnesium fixation plates and screws with plasma electrolytic oxidation (PEO) surface modification in contrast to titanium osteosynthesis. Surgery was performed on 24 merino mix sheep. The plates and screws were explanted en-bloc with the surrounding tissue after four and twelve weeks. The outcome of bone healing was investigated with micro-computed tomography, histological, immunohistological, and fluorescence analysis. There was no significant difference between groups concerning the bone volume, bone volume/ total volume, and newly formed bone in volumetric and histological analysis at both times of investigation. The fluorescence analysis revealed a significantly lower signal in the magnesium group after one week, although there was no difference in the number of osteoclasts per mm2. The magnesium group had significantly fewer vessels per mm2 in the healing tissue. In conclusion, the non-inferiority of WE43-based magnesium implants with PEO surface modification was verified concerning fracture healing under non-load-bearing conditions in a defect model. STATEMENT OF SIGNIFICANCE: Titanium implants, the current gold standard of fracture fixation, can lead to adverse effects linked to the implant material and often require surgical removal. Therefore, degradable metals like the magnesium alloy WE43 with plasma electrolytic oxidation (PEO) surface modification gained interest. Yet, miniplates of this alloy with PEO surface modification have not been examined in a fracture defect model of the facial skeleton in a large animal model. This study shows, for the first time, the non-inferiority of magnesium miniplates compared to titanium miniplates. In radiological and histological analysis, bone healing was undisturbed. Magnesium miniplates can reduce the number of interventions for implant removal, thus reducing the risk for the patient and minimizing the costs.

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near \"in situ\" structure around the exit hole, an \"emergency stop\" followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism.

A high strength and ductile Mg-Gd-Y-Zn-Zr alloy was designed and fabricated. The local strain evolution of the alloys during plastic deformation was analyzed using high-resolution digital image correlation (DIC). The results showed that the β particles, nano-sized γ\' phases, and LPSO phases were distributed in the as-extruded alloy and a bimodal microstructure was exhibited, including elongated un-dynamic recrystallized grains and fine dynamic recrystallized grains. With increasing extrusion ratio, the grain size remained, with the volume fraction of dynamic recrystallization of the as-extruded alloy increasing from 30% to 75%, and the as-extruded alloy exhibited a high strength-ductility synergy, which is attributed to the grain refinement, extensive β particles, and elongated block-shaped LPSO phases. The strain evolution analysis showed that a strain-transfer from un-DRXed regions to adjacent DRXed regions and LPSO phases can promote uniform plastic deformation, which tends to improve the ductility of the alloy.

Due to matching biomechanical properties and significant biological activity, Mg-based implants present great potential in orthopedic applications. In recent years, the biocompatibility and therapeutic effect of magnesium-based implants have been widely investigated in trauma repair. In contrast, the R&D work of Mg-based implants in spinal fusion is still limited. This review firstly introduced the general background for Mg-based implants. Secondly, the mechanical properties and degradation behaviors of Mg and its traditional and novel alloys were reviewed. Then, different surface modification techniques of Mg-based implants were described. Thirdly, this review comprehensively summarized the biological pathways of Mg degradation to promote bone formation in neuro-musculoskeletal circuit, angiogenesis with H-type vessel formation, osteogenesis with osteoblasts activation and chondrocyte ossification as an integrated system. Fourthly, this review followed the translation process of Mg-based implants via updating the preclinical studies in fracture fixation, sports trauma repair and reconstruction, and bone distraction for large bone defect. Furthermore, the pilot clinical studies were involved to demonstrate the reliable clinical safety and satisfactory bioactive effects of Mg-based implants in bone formation. Finally, this review introduced the background of spine fusion surgeryand the challenges of biological matching cage development. At last, this review prospected the translation potential of a hybrid Mg-PEEK spine fusion cage design.

In this work, the corrosion behavior of pure Mg, Mg3Ag, Mg6Ag, and MgZnYNd alloys in different fixatives (ethyl alcohol (EA), 85 % ethyl alcohol (85 % EA), 10 % neutral buffered formalin (10 % NBF), 4 % glutaric dialdehyde (4 % GD), and 4 % paraformaldehyde (4 % PFA)) was investigated to provide a valuable reference for the selection of fixatives during the histological evaluation of Mg implants. Through the hydrogen evolution test, pH test, and corrosion morphology and product characterization, it was found that corrosion proceeded slowest in the EA and 85 % EA groups, slightly faster in 4 % GD, faster in 10 % NBF, and fastest in 4 % PFA. After corrosion, the EA group surface remained unchanged, while the 85%EA group surface developed minor cracks and warping. The 4%GD fixative formed a dense needle-like protective layer on the Mg substrate. The 10%NBF group initially grew a uniform layer, but later developed irregular pits due to accelerated corrosion. In contrast, the 4%PFA solution caused more severe corrosion attributed to chloride ions. The main corrosion products in the EA and 85%EA groups were MgO and Mg(OH)2, while the other fixatives containing diverse ions also yielded phosphates like Mg3(PO4)2 and MgHPO4. In 4 % PFA, AgCl formed on the surface of Mg6Ag alloy after corrosion. Therefore, to minimize Mg alloy corrosion without compromising staining quality, EA or 85 % EA is recommended, while 4 % PFA is not recommended due to its significant impact.

This paper presents the methodology of measuring chip temperature in the cutting zone in the rough milling of magnesium alloys. Infrared measurements are taken to determine the effect of variable cutting speed, feed per tooth, and depth of cut on the maximum temperature of chips. Thermal images of chip temperature for a generated collective frame and corresponding histograms are presented. Chip temperatures are presented in numerical terms as median and average values; maximum and minimum values; range; and standard deviation. Box plots are also shown for selected machining conditions. The problems arising during signal recording with a mean emissivity coefficient ε = 0.13, a value which is dedicated during machining magnesium alloys, are discussed in detail. Chip temperatures obtained in the tests do not exceed approx. 420 °C. Therefore, the dry rough milling process carried out with carbide tools with different blade geometries can be considered safe for a wide range of machining parameters. The proposed methodology of chip temperature measurement and result processing is a new and effective approach to safety assessment in the dry milling of magnesium alloys.

Due to the absence of thermodynamic data concerning the Ag-Mg-Ti system in the existing literature, this study aims to fill this gap by offering the outcomes of calorimetric investigations conducted on ternary liquid solutions of these alloys. The measurements were performed using the drop calorimetry method at temperatures of 1294 K and 1297 K for the liquid solutions with the following constant mole fraction ratio: xAg/xMg = 9/1, 7/3, 1/1, 3/7 [(Ag0.9Mg0.1)1-xTix, (Ag0.7Mg0.3)1-xTix, (Ag0.5Mg0.5)1-xTix, (Ag0.3Mg0.7)1-xTix)], and xAg/xTi = 19/1 [(Ag0.95Ti0.05)1-xMgx]. The results show that the mixing enthalpy change is characterized by negative deviations from the ideal solutions and the observed minimal value equals -13.444 kJ/mol for the Ag0.95Ti0.05 alloy and xMg = 0.4182. Next, based on the thermodynamic properties of binary systems described by the Redlich-Kister model and the determined experimental data from the calorimetric measurements, the ternary optimized parameters for the Ag-Mg-Ti liquid phase were calculated by the Muggianu model. Homemade software (TerGexHm 1.0) was used to optimize the calorimetric data using the least squares method. Next, the partial and molar thermodynamic functions were calculated and are presented in the tables and figures. Moreover, this work presents, for comparative purposes, the values of the enthalpy of mixing of liquid Ag-Mg-Ti alloys, which were calculated using Toop\'s model. It was found that the best agreement between the modeled and experimental data was observed for the cross-sections xAg/xTi = 19/1 [(Ag0.95Ti0.05)1-xMgx] and xAg/xMg = 9/1 [(Ag0.9Mg0.1)1-xTix]. The results of the experiments presented in this paper are the first step in the investigation and future evaluation of the thermodynamics of phases and the calculation of the phase diagram of the silver-magnesium-titanium system.

The dissolution of metals, influenced by mechanical and chemical factors, plays a crucial role in various applications. Ultrasonic irradiation has been explored for its ability to enhance dissolution rates and modify surface characteristics. In this study, we investigate the dissolution of magnesium (Mg) and magnesium alloys under high-intensity focused ultrasound (HIFU) conditions with frequency sweeping (wobbling). Our findings reveal distinct effects of cavitation and acoustic streaming on the dissolution process. For pure magnesium, ultrasonic treatment significantly increases dissolution rates compared to silent conditions. Negative frequency sweeps result in the highest dissolution rates, linked to increased cavitation activity, while positive sweeps reduce dissolution rates but maintain acoustic streaming effects. The removal of surface oxides is accelerated in all sonication conditions. Macro- and micro-roughness patterns on the surface correspond to the wobbling frequency range, with wavelengths matching the average ultrasonic frequency. However, dissolution is not uniform across the sample, and preferential attack occurs at the focal point during negative frequency sweeps. In contrast, magnesium alloys exhibit lower dissolution rates than pure Mg. The alloy\'s mechanical properties make it less susceptible to cavitation erosion but more sensitive to acoustic streaming-induced dissolution. Grain boundaries are preferentially attacked, revealing differences between ductile pure Mg and the harder, more cavitation-resistant, alloy. This study highlights the complex interplay between cavitation and acoustic streaming in the dissolution of magnesium and its alloys under HIFU conditions, shedding light on the limits and potential applications of this technique, particularly in microstructure analysis.