Search Results (115)

In this study, a biodegradable Mg-Zn-Nd-Gd alloy was processed via multi-directional forging (MDF) to evaluate its microstructural evolution, mechanical performance, and corrosion behavior. Electron backscattered diffraction (EBSD) analysis was conducted to evaluate the influence of grain size and texture on mechanical strength and corrosion resistance. The average grain size decreased significantly from 118 ± 5 μm in the homogenized state to 30 ± 10 μm after six MDF passes, primarily driven by discontinuous dynamic recrystallization (DDRX). Remarkably, this magnesium (Mg) alloy exhibited a rare synergistic enhancement in both strength and ductility, with ultimate tensile strength (UTS) increasing by ~59%, yield strength (YS) by ~90%, while elongation improved by ~44% unlike conventional severe plastic deformation (SPD) techniques that often sacrifice ductility for strength. This improvement is attributed to grain refinement, dispersion strengthening from finely distributed Mg₁₂Nd and Mg₇Zn₃ precipitates, and texture weakening, which facilitated the activation of non-basal slip systems. Despite the mechanical improvements, electrochemical corrosion testing in Hank’s balanced salt solution (HBSS) at 37 °C revealed an increased corrosion rate from 0.1165 mm/yr in homogenized condition to 0.2499 mm/yr (after six passes of MDF. This was due to the higher fraction of low-angle grain boundaries (LAGBs), weak basal texture, and the presence of electrochemically active fine Mg₇Zn₃ particles. However, the corrosion rate remained within the acceptable range for bioresorbable implant applications, indicating a favorable trade-off between mechanical performance and degradation behavior. These findings demonstrate that MDF processing effectively enhances the strength–ductility synergy of Mg-rare earth alloys while maintaining a clinically acceptable degradation rate, thereby presenting a promising route for next-generation biomedical implants. Full article

Microstructural analysis of hot-compressed magnesium alloys is crucial for understanding the plastic formability of magnesium alloys during thermo-mechanical processing. Thermal compression tests and finite element simulations were conducted on a low rare-earth (RE) Mg-1.8Nd-0.4Zr-0.3Ca alloy. Multiple microstructural characterization techniques were employed to analyze slip systems, twinning mechanisms, dynamic recrystallization (DRX), and precipitate phases in the hot-compressed alloy. The results demonstrated that the equivalent strain distribution within compressed specimens exhibits heterogeneity, with a larger equivalent strain in the core. After thermal compression, the original microscopic structure formed a necklace-like structure. The primary DRX mechanisms comprise continuous dynamic recrystallization (CDRX), twin-induced dynamic recrystallization (TDRX), and particle-stimulated nucleation (PSN). Pyramidal slip and recrystallization constitute primary contributors to peak texture weakening and tilting. Mg₄₁Nd₅ and α-Zr phases enhanced dislocation density by impeding dislocation motion and promoting cross-slip activation. Hot compression provided the necessary thermal activation energy and stress conditions for solute atom diffusion and clustering, triggering dynamic precipitation of Mg₄₁Nd₅ phases. Full article

This study investigates the influence of RE elements on the room- and high-temperature properties of magnesium alloys. The effects of RE type, addition level, and multi-element alloying strategies were systematically analyzed to clarify the underlying strengthening mechanisms and processing pathways for optimizing Mg–RE alloys. RE elements enhance the mechanical and thermal properties of Mg alloys through crystal structure modification, formation of thermally stable dispersed phases, precipitation strengthening, and solid-solution strengthening. Compared with conventional alloying elements, RE additions offer distinct advantages in strengthening efficiency and overall performance. To fully exploit these benefits, new research paradigms that integrate machine learning and other advanced techniques are required, enabling the intelligent design of multicomponent alloy systems tailored to specific application requirements. Full article

This study systematically examines the influence of Zn addition (≤0.6 wt.%) on the microstructure and mechanical properties of Mg-2Al-0.8Sn-0.5Ca (wt.%) alloys. Minor Zn alloying marginally increases secondary phase fraction in as-cast alloys, with complete Zn dissolution achieved after solution treatment and asymmetric severe shear extrusion. Extruded alloys exhibit non-monotonic strength evolution with Zn content, peaking at 0.2 wt.% Zn (yield strength ≈ 235.1 MPa, ultimate tensile strength ≈ 289.2 MPa), while elongation reaches 16.1%. This strength enhancement originates from synergistic grain boundary, solid-solution, and dislocation strengthening mechanisms. These results demonstrate Zn’s critical role in optimizing the strength-ductility balance of rare-earth-free magnesium alloys. Full article

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

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

Magnesium-based biomaterials have emerged as highly promising candidates in the realm of biomedical engineering due to certain unique properties. However, their widespread application has been limited by a number of challenges, such as insufficient mechanical strength and rapid degradation rates. This study sought to advance the development of high-performance magnesium alloys by examining the microstructural evolution and associated strengthening mechanisms of Mg-Zn alloys modified with varying Nd contents. Comprehensive characterization techniques—including optical microscopy, XRD, and SEM/EDS—were employed to explain the influence of Nd additions on the microstructures. Mechanical performance was assessed through hardness testing, the RFDA method for elastic modulus, and tensile testing. The microstructural analysis of the as-cast Mg-Zn-Nd alloys revealed a complex phase composition comprising dendritic α-Mg, Mg₄₁Nd₅, and a Mg₃Nd binary phase enriched with rare earth elements. Notably, increasing the Nd content from 0.5% to 5% by weight resulted in a significant enhancement of hardness, reaching 59 HV compared to 42 HV in the base alloy. The tensile strength increased significantly from 62.9 MPa in the Mg-2.5Zn-0.5Nd alloy to 186.8 MPa in the Mg-2.5Zn-5Nd alloy. The elastic modulus values across all investigated alloys remained consistently comparable, which is expected as the elastic modulus is primarily determined by atomic bonding and is not significantly affected by alloying additions. These findings underscore the potential of Nd-alloyed Mg-Zn systems as viable, mechanically robust alternatives for next-generation biodegradable orthopedic implants. Full article

The effects of the gas tungsten arc (GTA) welding process on the microstructure and microhardness of two Mg-5Al-3RE and Mg-5Al-5RE experimental alloys (RE—rare earth elements) are presented. Both alloys were gravity-cast in a steel mould and GTA-welded in the same conditions. Analyses of the alloys’ microstructure were carried out by scanning electron microscopy (SEM+EDX) as well as X-ray diffraction (XRD). In as-cast conditions; both alloys were mainly composed of α-Mg; Al₁₁RE₃; and Al₁₀RE₂Mn₇ intermetallic phases. Additionally; α+γ eutectic (where γ is Al₁₂Mg₁₇) in the Mg-5Al-3RE alloy and an Al₂RE phase in the Mg-5Al-5RE material were revealed. The same phase composition was revealed for both alloys after the GTA welding process. The results of the dendrite arm size (DAS) and Vickers microhardness measurements were also described. Both welded materials exhibited an intensive size reduction of the structural constituents after GTA welding. About 75% smaller values of the dendrite arm spacing were revealed in the fusion zones of the investigated materials than in the as-cast conditions. The GTA welding process also influenced the microhardness of the experimental alloys and increased them by about 21% compared to the base metal; which was the consequence of the refinement of the structural constituents. Full article

Tensile tests of GW63K (Mg-6Gd-3Y-Zr) magnesium alloy under different heat treatment conditions were performed after immersion of the test specimens in 3.5 wt.% NaCl aqueous solution for periods up to 72 h. Results indicate that pitting corrosion should be responsible for the severe degradation of the tensile properties including yield strength, tensile strength (corrosion residual strength), and elongation within the testing time. The extreme depth of the corrosion pit was statistically related to corrosion residual strength. The variation of corrosion residual strength exhibited an exponential decay trend from 0 to 72 h. Furthermore, heat treatment enhanced the corrosion resistance of the GW63K alloy by inhibiting both the initiation and growth of corrosion pits, thereby improving the corrosion residual strength of the alloy. The critical working strength of GW63K alloy was significantly improved (increased to 192 MPa from 132 MPa) via heat treatment. Full article

This article evaluates the possibility of replacing creep-resistant magnesium Mg-Zn-RE-Zr alloys (EZ33) with Mg-Al-Ca-Sr alloys. (1) Background: Mg alloys with RE metals show excellent properties. Due to their high cost, new, more economical Mg alloys are being developed. Replacing RE metals with cheaper elements such as Al and Ca allows us to obtain high mechanical properties at elevated temperatures due to the tendency to form stable intermetallic phases. (2) Methods: Microstructure analysis (LM, SEM, TEM, and XRD) was performed and mechanical properties were tested at ambient and elevated temperatures. (3) Results: Increasing the Ca content and decreasing the Al content leads to the formation of a continuous skeleton of high-melting and brittle Ca-rich Laves phases and Sr-rich intermetallic phases and the formation of plate-like precipitates of the C15 phase inside the α-Mg solid solution. The crystallographic orientation of plate-like precipitates contributes to the blocking of dislocations in slip systems activated at elevated temperatures. Increasing the Ca and Sr content allows for the regulation of the Al concentration in the α-Mg, providing solution strengthening and stability of the α-Mg solid solution. These factors contribute to a significant improvement in creep resistance of Mg-Al-Ca-Sr alloys. (4) Conclusions: The strength properties and elongation at ambient temperature of the Mg alloys with Ca and Sr addition are comparable to those of the EZ33 alloy, and due to the presence of lighter alloying elements, a better specific strength is achieved. Ca-rich Mg-Al-Ca-Sr alloys exhibit better creep resistance at temperatures of up to 200 °C compared to the EZ33 alloy. Full article

The body-centered cubic (BCC)-structured magnesium–lithium (Mg-Li) alloy is the lightest metal material, but its mechanical properties are poor, especially its strength. In this study, the effect of adding rare earth Y on the microstructure and mechanical properties of as-cast BCC Mg-11Li-6Zn-xY (x = 0, 0.5, 1.2, and 2, in wt.%) alloys was investigated. The results revealed that massive amounts of nano-scale θ (MgLiZn) and/or θ’ (MgLi₂Zn) precipitated inside the grains, and some θ phases precipitated at the grain boundaries in the Mg-11Li-6Zn alloy. With the addition of Y, W phases formed at the grain boundary, their content gradually increased with the Y concentration, and the grain size decreased simultaneously. The Mg-11Li-6Zn-0.5Y alloy exhibited higher ultimate tensile strength (190 MPa) and elongation (27%) at room temperature than those (170 MPa and 22%) of the Mg-11Li-6Zn alloy, presenting improvements of 11.8% and 22.7% in strength and ductility, respectively. The improvements in the mechanical properties of the Mg-11Li-6Zn alloy achieved by adding less Y could be attributed to the formation of moderate W phases and a reduction in grain size. However, once the addition of Y became excessive, the mechanical properties of the Mg-11Li-6Zn-1.2Y alloy were reduced due to the formation of too many reticular W phases. In addition, the Mg-11Li-6Zn-2Y alloy containing the highest Y content had the lowest ultimate tensile strength, 163 MPa, and highest ductility, 38%, due to the combined effect of the most reticular W phases and the smallest grains. Furthermore, the fracture morphology of the Mg-11Li-6Zn alloy displayed apparent necking, which became insignificant after the addition of Y, indicating that this addition could improve its uniform plastic deformation ability. Full article

Magnesium (Mg) and its alloys have emerged as promising biomaterials for orthopedic and cardiovascular applications, thanks to their good biodegradability, biocompatibility, and mechanical properties close to that of natural bone. However, the rapid degradation of Mg in physiological environments and limited mechanical performance tend to compromise the structural integrity of implants before healing is complete. These drawbacks have been heavily limiting the application of Mg and its alloys as biomaterials. In this paper, we review recent advancements in two common solutions to these problems: alloying and surface treatment, with a focus on controlling the corrosion resistance, mechanical performance, and biocompatibility of Mg-based biomaterials. Full article

Magnesium and its rare-earth alloys are extensively studied for their lightweight properties and high specific strength, making them attractive for aerospace, automotive, and biomedical applications. However, their hexagonal close-packed structure leads to a strong basal texture, limiting plasticity and formability at room temperature. Considerable research has been devoted to texture control strategies, including alloying, thermomechanical processing, and recrystallization mechanisms, yet a comprehensive understanding of their effects remains an ongoing research focus. This review summarizes recent advances in texture regulation of rare-earth magnesium alloys, focusing on the role of RE elements (Gd, Y, Nd, Ce) and non-RE elements (Zn, Ca) in modifying basal texture and enhancing mechanical properties. The influence of key processing techniques, such as extrusion, rolling, equal channel angular pressing, and rotary shear extrusion, is discussed in relation to their effects on recrystallization behavior. Additionally, the mechanisms governing texture evolution, including continuous dynamic recrystallization, discontinuous dynamic recrystallization (DDRX), and particle-stimulated nucleation, are critically examined. By integrating recent findings, this review provides a systematic perspective on alloying strategies, processing conditions, and recrystallization pathways, offering valuable insights for the development of high-performance magnesium alloys with improved formability and mechanical properties. Full article

Hydrogen can be easily captured by the rare-earth (RE) elements in hydrogen-rich environments, which significantly affect the phase compositions and mechanical performance of Mg-RE based alloys. However, the morphology of RE hydrides and their orientation relationships (ORs) with the Mg matrix have not been well explained. Here, a stable face-centered cubic (FCC) ${\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2$ hydride was introduced and uniformly distributed in a Mg-15Gd-2.5Y-1Al alloy after hydrogenation treatment at 500 °C and 2 MPa for 40 h. The plate-like ${\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2$ hydride with six variants was identified to exhibit an OR with the magnesium (Mg) matrix, which is ${\left[0001\right]}_{\mathrm{M}\mathrm{g}}$//${\left[001\right]}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$, ${\left(10\overline{1}0\right)}_{\mathrm{M}\mathrm{g}}{10.5}^{\circ }$ from ${\left(002\right)}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$, ${\left(1\overline{2}10\right)}_{\mathrm{M}\mathrm{g}}{10.5}^{\circ }$ from ${\left(020\right)}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$. Further crystallographic matching calculations based on the edge-to-edge matching model suggest that such an OR is energetically favorable and provides the actual interface between the RE hydrides and the Mg matrix during precipitation. Our findings offer new insights into the microstructural regulation of Mg alloys in hydrogenation environments. Full article

Rare earth elements (REEs) possess unique physical and chemical properties that render them indispensable in various industries, including electronics, energy production and storage, hybrid and electric vehicles, metallurgy, and petro-chemical processing. The criticality of REE underscores the need to enhance the efficiency of primary resource extraction and promote circularity through increased recycling from secondary sources. This paper provides a brief overview of REE recovery from secondary sources, particularly waste from electronic and electric equipment (WEEE). The discussion encompasses direct reuse of magnets, short-loop recycling (direct recycling), hydro- and pyrometallurgical processes, highlighting microwave (MW) technology. Original results are presented, focusing on the recovery of neodymium (Nd) from permanent magnet scraps from hard disk drives (HDD-PC) using microwave-assisted liquid metal extraction (LME) with magnesium (Mg) as the extractant. The subsequent separation of Nd from the Mg-Nd alloy via vacuum Mg distillation that is reused in the process is described. The experimental study demonstrates that the LME process, conducted in a microwave furnace, is a viable method for recovering Nd from permanent magnet scraps, which are essential for reducing the environmental impact of REE extraction and promoting a circular economy. By separating Nd from the alloy through vacuum distillation (450–550 mmHg), at temperatures of 850–900 °C for 8 h, a Nd sponge with a content of 95–98 wt.% Nd was obtained. The extracted content of Nd in the Mg alloy increases with increasing temperature and holding time. It was found that ≈ 97% of the Nd in the scrap was extracted from 2 to 5 mm crushed scrap at 800 °C for 8 h, using a LiF-LiCl-MgF₂ protecting flux in a furnace Ar atmosphere. Full article