Search Results (1,827)

In the medical field, magnesium (Mg) alloys have been widely used due to their excellent antibacterial properties and biodegradability. However, in the marine environment, the antibacterial effect may be greatly attenuated, and consequently, microorganisms in the ocean are likely to adhere to the surface of Mg alloys, resulting in biocorrosion damage, which is really troublesome in the maritime industry and can even be disastrous to the navy. Currently, there is a lack of research on the biocorrosion of Mg alloys that may find important applications in marine engineering. In this paper, the biocorrosion mechanism of the Mg alloy Mg-3Nd-2Gd-Zn-Zr caused by Chlorella vulgaris (C. vulgaris), a typical marine microalga, was studied. The results showed that the biomineralization process in the artificial seawater containing a low concentration of C. vulgaris cells was accelerated compared with that in the abiotic artificial seawater, leading to the deposition of CaCO₃ on the surface to inhibit the localized corrosion of the Mg alloy, whereas a high concentration of C. vulgaris cells produced a high content of organic acids at some sites through photosynthesis to significantly accelerate the surface film rupture at some sites and severe localized corrosion there, but meanwhile, it resulted in the formation of a more protective biomineralized film in the other areas to greatly alleviate the corrosion. The contradictory biocorrosion behaviors on the Mg-3Nd-2Gd-Zn-Zr alloy induced by C. vulgaris were finally explained by a mechanism proposed in the paper. Full article

Improving the corrosion resistance of magnesium (Mg) alloys is a long-term challenge, especially when cost-effectiveness is taken into account. In this work, Mg-1Bi and Mg-1Sn extruded alloys are prepared, and the effects of cost-effective Bi and Sn on the corrosion behavior of Mg alloys are comparatively studied. The corrosion resistance of the Mg-1Sn alloy (P_H: 2.83 ± 0.19 mm y⁻¹) is better than that of the Mg-1Bi alloy (P_H: 13.75 ± 1.12 mm y⁻¹), being about five times greater. In addition to the relatively low dislocation density in Mg-1Sn alloy, the difference in corrosion resistance is mainly attributed to two aspects of influence brought about by the addition of Sn and Bi. The Mg₂Sn phase introduced by the addition of Sn has a potential difference (PD) of ~30 mV, which is significantly lower than that (~90 mV) of the Mg₃Bi₂ phase introduced by adding Bi, thereby weakening the micro-couple corrosion tendency of the Mg-1Sn alloy. The addition of Bi has little effect on the corrosion film, while the addition of Sn makes the corrosion film on the Mg-1Sn alloy contain SnO₂, improving the compactness of the corrosion film and thereby enhancing the corrosion protection effect. Full article

Mg-Li-based dissoluble metal is a promising material for preparing dissoluble magnesium alloy wires. However, there are few reports on the development of Mg-Li dissoluble magnesium alloy wires so far. In this paper, the mechanical properties and dissoluble properties of as-drawn and annealed LA141-0.5Cu wires were investigated in detail. It was found that the tensile strength of the LA141-0.5Cu wires decreased from 160 MPa to 127 MPa and the elongation increased from 17% to 22% after annealing. The difference in corrosion rates (93 °C/3% KCl solution) between the as-drawn wires and annealed wires is not significant, with values of 5.1 mg·cm⁻²·h⁻¹ and 4.5 mg·cm⁻²·h⁻¹, respectively. This can be explained as follows: after annealing, the number of dislocations in the wire decreases, the strength decreases, and the plasticity increases. The reason why the wires have a significant corrosion rate is that there is a large potential difference between the Cu-containing second phase and the magnesium matrix, which forms galvanic corrosion. The decrease in dislocation density after annealing leads to a slight reduction in the corrosion rate of the wires. This work provides a qualified material for fabricating temporary blocking knots for the exploitation of unconventional oil and gas resources. Full article

This work expands the processing window of the laser powder bed fusion (LPBF) processing of WE43 magnesium alloy by evaluating laser powers and scanning speeds up to 400 W and 1200 mm/s, and their effect on densification, microstructure, and electrochemical performance. Relative density of 99.9% was achieved for 300 W and 800 mm/s, showing that the use of high laser power is not a limitation for the manufacturing of Mg alloys, as has been usually considered. Microstructural characterisation revealed refined grains and the presence of RE-rich intermetallic particles, while microhardness increased with height due to thermal gradients. Electrochemical testing in 3.5 wt.% NaCl solution, a more aggressive media than those already used, indicated that the corrosion of samples with density values below 99% is conditioned by the porosity; however, above this value, in the WE43, the corrosion evolution is more related to the microstructure of the samples, according to electrochemical evaluation. This study demonstrates the viability of high-energy LPBF processing for WE43, offering optimised mechanical and corrosion properties for biomedical and structural applications. Full article

In this study, the atmospheric corrosion behavior of AZ31 magnesium alloy exposed in Sanya and Nansha for one year was investigated. While existing studies have characterized marine corrosion of magnesium alloys, the synergistic corrosion mechanisms under extreme tropical marine conditions (simultaneous high Cl⁻, rainfall, and temperature fluctuations) remain poorly understood—particularly regarding dynamic corrosion–product evolution. The corrosion characteristics and behavior of AZ31 magnesium alloy exposed in Sanya and Nansha were evaluated using X-ray photoelectron spectroscopy, X-ray diffraction, electrochemical measurements, scanning electron microscopy, and weight loss tests. The results showed that the main components of corrosion products were MgCO₃·xH₂O(x = 3, 5), Mg₅(CO₃)₄(OH)₂·4H₂O, Mg₂Cl(OH)₃·4H₂O, and Mg(OH)₂. The corrosion rate exposed in the Nansha was 26.5 μm·y⁻¹, which was almost two times than that in Sanya. Localized corrosion is the typical corrosion characteristic of AZ31 magnesium alloy in this tropical marine atmosphere. This study exposes the dynamic crack–regeneration mechanism of corrosion products under high-Cl⁻-rainfall synergy. The corrosion types of AZ31 magnesium alloy in this tropical marine atmosphere were mainly represented by pitting corrosion and filamentous corrosion. Full article

This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al₂O₃ regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article

This study examined the comprehensive properties of Mg-Zn-Nd-Zr alloys in order to achieve both high strength and thermal conductivity simultaneously. The impact of rolling on the microstructure, mechanical properties, and thermal conductivity was analyzed for Mg-5Zn-xNd-0.4Zr alloys (x = 1, 2). The results indicate that the addition of Nd promotes the formation of the W phase (Mg₃Zn₃RE₂), which contributes to grain boundary strengthening and enhances the overall strength. Moreover, dynamic precipitation during the rolling process leads to the formation of nanoscale MgZn₂ and Zn₂Zr phases, significantly improving both the strength and thermal conductivity. After rolling, both the Mg-5Zn-1Nd-0.4Zr (ZNK510) and Mg-5Zn-2Nd-0.4Zr (ZNK520) alloys exhibited a notable enhancement in thermal conductivity, with ZNK520 demonstrating superior properties due to its higher Nd content. This study highlights that optimizing alloy composition and phase evolution through rolling can markedly enhance both the mechanical and thermal properties, offering a promising strategy for the development of high-performance magnesium alloys. Full article

The corrosion behavior of an additively manufactured Mg-1Zn alloy was investigated in both the transverse and longitudinal directions relative to the build direction, in the as-built condition and after annealing at 350 °C for 24 h under high vacuum. Microstructural characterization using XRD and SEM revealed the presence of magnesium oxide (MgO) and the absence of intermetallic second-phase particles. Optical microscopy (OM) images and Electron Backscatter Diffraction (EBSD) maps showed a highly complex grain morphology with anomalous, anisotropic shapes and a heterogeneous grain size distribution. The microstructure includes grains with a pronounced columnar morphology aligned along the build direction and is therefore characterized by a strong crystallographic texture. Electrochemical techniques, including PDP and EIS, along with gravimetric H₂ collection, concluded that the transverse plane exhibited greater corrosion resistance compared to the longitudinal plane. Additionally, an increase in cathodic kinetics was observed when comparing as-built with heat-treated samples. Full article

Biodegradable magnesium alloys have emerged as promising alternatives to permanent metallic implants due to their unique combination of mechanical compatibility with bone and complete resorption, addressing the persistent issues of stress shielding and secondary removal surgeries. This review critically examines the historical development of magnesium-based biomaterials, highlighting advances in alloy design, manufacturing processes, and surface engineering that now enable tailored degradation and improved clinical performance. Drawing on recent clinical and preclinical studies, we summarize improvements in corrosion resistance, mechanical properties, and biocompatibility that have supported the clinical translation of magnesium alloys across a variety of orthopedic and emerging medical applications. However, challenges remain, including unpredictable in vivo degradation kinetics, limited long-term safety data, lack of standardized testing protocols, and ongoing regulatory uncertainties. We conclude that while magnesium-based biomaterials have advanced from experimental concepts to clinically validated solutions, further progress in personalized degradation control, real-time monitoring, and harmonized regulatory frameworks is needed to fully realize their transformative clinical potential. Full article

The initial reactivity of a multiphase ZnAlMgSi coating with an Al content > 30 wt.% was studied by in situ reflective microscopy under alternating applied potentials +50 mV/−50 mV vs. open-circuit potential in 5 wt.% NaCl and 5 wt.% Na₂SO₄ aqueous solutions. In both environments, galvanic coupling between different coating phases and the anodic behavior decreased in the order binary ZnAl > binary Zn/Zn₂Mg > Zn₂Mg > Al(Zn); dendrites were evidenced for the coating exposed alone as well as in galvanic coupling with steel. Contrary to the observations known for Zn-rich ZnAlMg coatings, pure Zn₂Mg was less reactive than the pure ZnAl phase, underlining the importance of the microstructure for reactivity. Si-needles were systematically cathodic, and Al(Zn) dendrites have shown cathodic behavior in some couplings. In the configuration of coupling with steel, corrosion started at the interfaces “binary ZnAl/steel substrate” or “binary ZnAl/Si particle”. The distribution and nature of the corrosion products formed during the experiment were assessed using X-ray microanalysis in scanning electron microscopy and confocal Raman microscopy. In the sulfate environment, a homogenous and stable corrosion product layer formed from the first steps of the degradation; this was in contrast to the chloride environment, where no surface film formed on the dendrites. Full article

In this study, 3D Mg scaffolds were obtained by the spark plasma sintering (SPS), and a calcium phosphate coating was then obtained on the samples by the plasma electrolytic oxidation. A hybrid coating with vancomycin, zoledronic acid, and menaquinone MK-7 was formed to improve biocompatibility. The mechanical properties of the formed specimens were studied. According to XRD, XRF, SEM, EDS, and OSP studies obtained scaffolds have developed morphology and contain hydroxyapatite as well as bioactive substances. Formation of coatings improves the wettability of samples (contact angle decreases from 123.8 ± 3.1° to 26.9 ± 4.1°) and increases the surface roughness by more than 3 times. This makes them promising for use as a new generation of implantation materials. The results are important for the development of personalized implants with improved functional characteristics. Full article

When a high-speed rotating projectile faces high impact loads, the sensitive parts of the control system can get damaged, resulting in operational failure. It is crucial to develop a unique buffer structure that offers impact resistance and has a small contact area. An annularly distributed multi-sphere point contact structure was designed and fabricated on a magnesium alloy substrate based on the Hertz contact theory. The accuracy of the finite element numerical model, constructed using Abaqus/Explicit, was verified through hydraulic impact tests. The impact mechanical properties of the structure were studied by analyzing the influence of the number, diameter, and cavity radius of hemispheres using an experimentally verified finite element model. The axial and radial deformations of the structure were compared and analyzed. The research findings indicate that the deformation and impact resistance of the structure can be greatly influenced by increasing the number of hemispheres, enlarging the hemisphere diameter, and incorporating internal cavities. Specifically, with 6 hemispheres, each with a diameter of Φ 6 mm and a cavity radius of R1.5 mm, the axial and radial deformations are only 1.03 mm and 3.02 mm, respectively. The contact area of a single hemisphere is 7.16 mm². The study offers new perspectives on choosing buffer structures in high-impact environments. Full article

Magnesium (Mg) alloys have demonstrated tremendous potential in biomedical applications, emerging as promising metallic biomaterials due to their biocompatibility, degradability, and favorable mechanical properties. However, their practical implementation faces significant limitations stemming from mechanical performance degradation and premature fracture failure caused by complex physiological interactions, including flow erosion, corrosion fatigue, stress coupling effects, and dynamic wear under bodily conditions. Surface coating technology has been recognized as an effective strategy to prevent direct contact between magnesium substrates and corrosive media. This review systematically examines the fundamental degradation mechanisms of magnesium alloys in both vivo and vitro environments, presents recent advances in surface modification coatings for magnesium alloys, and critically analyses the interaction mechanisms between modified layers and electrolyte solutions. Special emphasis is placed on revealing the formation mechanisms, structural characteristics, and fracture behaviors of conversion coatings. Furthermore, the study discusses the current challenges in biomedical surface modification of magnesium alloys, proposes potential solutions to enhance their clinical applicability, and outlines future research directions to fully exploit the development potential of these advanced biomaterials. Full article

Superplastic materials are characterised by extreme lightness and remarkable ductility. Instead of a punch, a gas is used to push the sheet into the die cavity, and it is precisely regulated to control the material’s strain rate. Forming a superplastic material while maintaining a high strain rate sensitivity index requires the forming gas to follow a precise pressure–time loading curve. This can be excellently predicted with the aid of the finite element method (FEM). Therefore, for the superplastic material to exhibit its best formability throughout the entire process, it is necessary to control the strain rate step by step to keep the maximum strain rate within the material’s optimal superplastic range. In this work, the results of a superplastic-forming process used to create a hemispherical shell are presented. This was carried out using both a circular blank of uniform thickness and a blank with a conical cross-section. The analysis was performed using finite element modelling. Specifically, the results obtained using 3D analysis were compared with those obtained using axisymmetric analysis for conditions of axial symmetry. Using the conical cross-section blank helped achieve a more uniform thickness distribution in the produced hemispherical shell. The success of the numerical activity was validated through results from appropriate experimental work conducted on the magnesium alloy AZ31. The results show that, by employing a blank characterised by a conical section profile, the thickness distribution appears more uniform than that of a constant-thickness blank. Full article

Plasma electrolytic oxidation (PEO) is an advanced electrochemical surface treatment technology. It can effectively improve the corrosion resistance of magnesium and its alloys. This paper aims to form protective PEO coatings on an AZ31 substrate with different electrolytes, while monitoring the micro-discharge evolution by noise intensity and morphology analysis. By setting the PEO parameters and monitoring process characteristics, such as current density, spark appearance, and noise intensity, it was deduced that the PEO process consists of the following three stages: anodic oxidation, spark discharge, and micro-arc discharge. The PEO oxide coating formed on the AZ31 alloy exhibits various irregular volcano-like structures. Oxygen species are uniformly distributed along the coating cross-section. Phosphorus species tend to be enriched inwards to the coating/magnesium substrate interface, while aluminum piles up towards the surface region. Surface roughness of the PEO coating formed in the silicate-based electrolyte was the lowest in an arithmetic average height (Sa) of 0.76 μm. Electrochemical analysis indicated that the corrosion current density of the PEO coating decreased by about two orders of magnitude compared to that of untreated blank AZ31 substrate, while, at the same time, the open-circuit potential shifted significantly to the positive direction. The corrosion current density of the 10 min/400 V coating was 1.415 × 10⁻⁶ A/cm², approximately 17% lower than that of the 2 min/400 V coating (1.738 × 10⁻⁶ A/cm²). For a fixed 10 min treatment, the longer the PEO duration time, the lower the corrosion current density. Finally, the tested potentiodynamic polarization curve reveals the impact of different types of PEO electrolytes and different durations of PEO treatment on the corrosion resistance of the oxide coating surface. Full article