The quest for efficient energy storage solutions has catalyzed interest in magnesium-ion batteries (MIBs), which utilize the nature of magnesium to achieve higher volumetric capacity, improved safety and cost advantages. However, significant challenges remain, including severe polarization caused by the high charge density of Mg2+ and limited ion diffusion in cathode materials. In this study, we present a strategic approach to address these challenges by doping vanadium tetrasulfide (VS4) with copper. This doping effectively expands the interlayer spacing, relieving steric hindrance to Mg2+ ion diffusion and introduces anion vacancies that serve as additional diffusion pathways. These vacancies promote simultaneous cation-anion redox reactions and facilitate multi- electron transfer during electrochemical processes. This enhancement of diffusion and reaction kinetics significantly boosts the overall electrochemical performance. Based on this, copper-doped VS4 (CVS) achieves a high discharge capacity of similar to 130 mAh g(-1) at a current density of 50 mA g(-1) and exhibits exceptional cycling stability, maintaining performance over 1000 cycles at 1 A g(-1) . This dual optimization of ion diffusion and redox kinetics offers a promising solution to the intrinsic challenges of MIBs and provides a basis for addressing similar limitations in other divalent ion systems.

A CaCO3 coating with good anticorrosion and adhesion performance was fabricated via ultrasound-assisted chemical conversion on AZ41 magnesium alloy, with a water-bath treated coating as a control. The coating formed on AZ41 mainly consists of an outer CaCO3 layer and an inner (Ca, Mg)CO3 layer. Surface characterizations were carried out to obtain the morphology and the chemical composition, mechanical tests were also adopted to assess the hardness and the adhesion of the coating prepared. Afterwards, the long-term corrosion resistance was investigated via electrochemical methods in the chloride-containing Portland cement system. Results show that the ultrasound-assisted coating exhibits higher mechanical properties. In addition, the corrosion resistance of the ultrasound-assisted coating is also higher than that of the bare AZ41 alloy and the water-bath treated coating. This could be due to the formation of a much more compact CaCO3 coating on AZ41 Mg alloy, which is mainly benefit from the assistance of the ultrasound. Ultrasound accelerates the nucleation of CaCO3 crystals and assists the removal of hydrogen bubbles. Additionally, corrosion mechanism was suggested and discussed for the CaCO3 coating.

In this study, Mg-13.2Gd-4.3Ni alloys containing continuous bulk-shaped long-period stacking ordered (LPSO), lamellar LPSO, and a small amount of eutectic phase were prepared, and the evolution of microstructure at different extrusion temperatures and its influence on mechanical and degradation properties as well as corrosion mechanism were investigated. Preheating before extrusion can effectively promote the precipitation of lamellar LPSO in matrix. EX400 with higher volume fraction of non-DRXed grains exhibited higher strength, which was mainly due to strong texture, high dislocation density, and high volume fraction of lamellar LPSO. The EX420 with higher volume fraction of DRXed grains showed higher degradation rate, which was mainly due to the higher density of grain boundary. The EX400 exhibited excellent comprehensive properties with tensile yield strength (TYS) of 334 MPa, ultimate tensile strength (UTS) of 484 MPa and elongation (EL) of 7.4%, ultimate compressive strength (UCS) of 638 MPa and compressive yield strength (CYS) of 443 MPa, degradation rate of 86.1 mg/cm2/h at 93 °C in 3 wt.% KCl solution.

A simple one-step anticorrosion Portland cement (PC)-based coating with an autogenerated oxide film on the surface of Mg alloy was successfully prepared in this study. The anticorrosion of coated Mg alloys was assessed by several electrochemical methods including open circuit potential, electrochemical impedance spectroscopy, and cyclic potentiodynamic polarization. The morphology and composition of PC-based coatings were characterized via scanning electron microscopy and X-ray diffraction. The composition of the autogenerated oxide film was analyzed via X-ray photoelectron spectroscopy. Results show that the PC-based coatings can significantly enhance the corrosion resistance of AZ41 Mg alloy due to the synergetic effect of PC-based coating and autogenerated oxide film. Particularly, the quality of oxide film plays a dominant role in determining anticorrosion of Mg alloy. Furthermore, the addition of metakaolin and dolomite enhances the resistance of PC-based coating and meanwhile, MoO 4 2- ions from PC-based coating can adsorb in the oxide film, improving the quality of the oxide film. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Mg-Gd-Y-Zr is an important lightweight material in the aerospace field. However, the engineering applications of large-scale Mg-Gd-Y-Zr alloy components are significantly limited by macrosegregation and microstructure coarsening during the casting process. In recent years, wire-arc directed energy deposition (DED), which has high design and manufacturing freedom, provides a new route to manufacture large-scale metal parts. In this work, a dilute Mg-3.2Gd-0.6Y-0.5Zr (wt.%) alloy, which had a degree of alloying comparable to AZ31 commercial alloys, was fabricated using a wire-arc DED process based on tungsten inert gas (TIG) welding, the microstructure evolution, tensile properties, and impact toughness were investigated. Due to the multiple grain refinement effects, the DED sample displayed a fine-grain structure (12.3 ± 7.4 μm), which was comparable to that of the wrought counterpart. Combined with the ductilizing effects of the fine grain and the Gd/Y solutes, the DED sample achieved a high ductility, which was better than most reported additive-manufactured Mg alloys as well as wrought Mg alloys. The good plastic deformation capacity also endowed the DED sample with good crack propagation resistance under dynamic impact load. We hope this work can help guide the further development of high-performance Mg alloys that are specially designed for the wire-arc DED additive manufacturing process.

As-extruded Mg-Er-Ni alloys with different volume fractions of long-period stacking ordered (LPSO) phase and density of lamellar gamma' phase were prepared, and the microstructure, mechanical, and degradation properties were investigated. Coupling the bulk LPSO phase and the lamellar gamma' phase, and controlling the dynamic recrystallization processes during deformation by adjusting the volume fraction of LPSO and the density of the gamma' phase, a synergistic increase in strength and degradation rate can be achieved. On the one hand, the increase in corrosion rate was related to the increased volume fraction of the bulk LPSO phase and the densities of the lamellar gamma' phase, which provide more galvanic corrosion. Moreover, high densities of the lamellar gamma' phase can provide more corrosion interface by inhibiting the recrystallization process to refine dynamic recrystallized (DRXed) grains during the hot extrusion. On the other hand, the ultimate tensile strength (UTS) and tensile yield strength (TYS) of the Mg-Er-Ni alloy increased from 345 and 265 MPa to 514 MPa and 358 MPa, respectively, which was mainly attributed to grain boundary and texture strengthening, bulk LPSO phase and lamellar gamma' phase strengthening. Overall, Mg-14Er-4Ni alloy, which contains the highest volume fraction bulk LPSO phase and the densities of lamellar gamma' phase, realized a synergistic enhancement of strength and degradation rate. The UTS, TYS, and degradation rate of Mg-14Er-4Ni were 514 MPa, 358 MPa, and 142.5 mg cm (-2) h (-1) (3 wt% KCl solution at 93 degrees C), respectively. This research provides new insight into developing Mg alloys with high strength and degradation rates for fracturing tool materials in the application of oil and gas exploitation in harsh environments. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

In this study, a novel CaCO3/Mg(Al)O coating system was successfully synthesized via one-step pulse electrodeposition. The thickness of inner passivation layer and outer CaCO3 layer was tailored by modulating the pulse voltage. Anticorrosion performance of the coated Mg alloy was assessed by both electrochemical methods and embedment tests. The coated Mg alloy demonstrated improved corrosion resistance, attributed to the synergistic impact of a compact outer CaCO3 layer and an Al-assisted inner passivation layer. Both layers' quality primarily governed the alloy's anticorrosion performance. Remarkably, embedment tests revealed a re-passivation phenomenon instead of corrosion, with its mechanism discussed comprehensively.

This study investigates the formation of a high-potential Mg2Bi2Ca phase in MgBixCa2.5x (x = 0.15, 0.22, 0.37 at. %). The rate of degradation can be increased by exploiting the electrochemical corrosion formed between this phase and the magnesium matrix, while the presence of this phase also improves the dynamic recrystallization process of the alloy during extrusion-induced deformation, thereby enhancing its plasticity. The MgBi0.15Ca0.37 alloy exhibited the best comprehensive mechanical properties after annealing, with a yield strength and a tensile strength of 170 MPa and 225 MPa, respectively, and an elongation of 32.9%. Moreover, it recorded a higher increase in the rate of degradation, 150%, at 25 degrees C than the extruded state. We also investigated the mechanism of influence of the content, distribution, and morphology of the Mg2Bi2Ca phase in the alloy on its mechanical and degradation-related properties. The work here provides insights into the development of highly ductile and low-cost candidate materials for fracturing tools.

Hot deformation behavior, the corresponding microstructure evolution, and degradation properties of a weaktextured Mg-Er-Ni alloy containing a high-volume fraction of Ni-LPSO phases, have been investigated. Hot deformation behavior has been carried out in the temperatures range of 370 460 degrees C and strain rates range of 0.001 1 s(-1). Flow stress-strain curves of high strain rate cases show a continuous increase trend without a steady or a peak stage, while that of low strain rate cases show an obvious dynamic softening after peak stress. Based on flow stress-strain curves, materials constants calculated by an Arrhenius-type constitutive equation, show a high n and Q compared to those of high-volume fraction alpha-Mg matrix Mg alloys. Optimal processing windows, based on the dynamic material model, is determined as high temperature domains. As for microstructure evolution, a complete recrystallization and dispersive Ni-LPSO fragments for high temperature & low strain rates while a restricted recrystallization and a streamline distribution LPSO phase for high temperature & high strain rates are observed. Varying degrees of continuous dynamic recrystallization, particle induced nucleation mechanism, as well as coordinated deformation of LPSO through kinking and bending account for the strain-rate-dependence hot deformation mechanism. As a result, dispersive Ni-LPSO fragments at low strain rates provide more degradation channels for the alpha-Mg matrix and thus possess better a degradation rate than the streamlined LPSO at high strain rates.

A systematic investigation was undertaken to explore the influence of microstructure evolution in the as-cast, heat-treated, and as-extruded on the corrosion properties of a high-performance Mg-5.6Dy-3.1Ni alloy, which includes two intermediate phases. It was found that degradation rate of both as-cast and heat treated alloys primarily depended on the distribution of the LPSO and Mg6Ni intermetallic phases. For the as-extruded alloy, the degradation rate depended on both the distribution of the LPSO and Mg6Ni phases and the grain refinement of the matrix. Compared with as-cast alloy, the corrosion barrier was formed and inhibited the corrosion propagation after heat treatment. This was attributed to the network distribution of the LPSO phase, coupled with a uniform distribution of Mg6Ni phase. After extrusion, After extrusion, the streamlined distribution of the stripped LPSO phase. This led to a reduced corrosion barrier in the extrusion direction (ED) sample, resulting in a higher degradation rate compared to the transverse direction (TD) sample. Furthermore, the LPSO phase and grain refinement after extrusion provided a denser corrosion product film to retard the degradation rate in the TD sample. A high mechanical properties Mg-5.6Dy-3.1Ni alloy with different degradation rates in the as-cast, heat-treated, and along the extrusion direction and in the transverse direction was developed.

In this work, a prediction model, which can be used to reveal the corrosion mechanism and behavior of Mg-RE-Ni alloys, was successfully developed with machine learning. The model is constructed based upon the microstructure parameters of LPSO phase, and the accuracy of the prediction model is greater than 93%. The results agree well with the literature when it is used to study the relationship of composition-structure-corrosion behavior of Mg-RE-Ni alloys. This work solves the shortcomings of experimental studies, which provide a route to quantitively analyze and reveal the corrosion mechanism of Mg-RE-Ni alloys.

Mg-Gd-Y-Zn-Zr alloy is an important lightweight material in the aerospace field. Wire arc additive manufacturing (WAAM) provides a new route to fabricate large Mg alloy components. Here, a Mg-8Gd-4Y–1Zn-0.5Zr (wt.%) alloy was fabricated using WAAM based on the cold metal transfer (CMT) process. Subsequently, a short-time solid solution + aging treatment was designed to tailor the microstructure. In the as-fabricated condition, the microstructure mainly consisted of fine α-Mg, network (Mg,Zn)3(Gd,Y) eutectic phase, and lamellar γ′ basal precipitate. After 500 °C-1 h short-time solid solution, the eutectic phase rapidly dissolved, the long-period stacking ordered (LPSO) phase formed, and the fine grain was maintained. Due to the good deformation capacity of the fine grains and the kinking deformation capacity of the LPSO phase, the ductility was significantly improved from 5.2 ± 0.4% to 15.5 ± 1.1%. After further 200 °C-64 h artificial aging, dense β′ prismatic precipitates formed. Thanks to the synergistic strengthening of the fine grains and β′ prismatic precipitates, a yield strength of 242 ± 4 MPa was achieved. However, the kinking deformation of the LPSO phase was inhibited, resulting in a drastic decrease of ductility to 6.1 ± 0.5%. Overall, the combination of strength and ductility of the CMT-based WAAM-processed Mg-Gd-Y-Zn-Zr alloy under an optimized heat treatment regime can be superior to those of the cast Mg-Gd-Y-Zn-Zr alloys with similar contents of Gd and Y elements. This work can guide further performance optimization for WAAM-processed Mg-Gd-Y-Zn-Zr alloys.

To address the limited corrosion resistance of magnesium alloys, calcium phosphorus coatings are frequently applied to their surfaces as a means of compensating for this drawback. However, cracking of traditional calcium phosphorus coatings greatly affects their protective properties. In this research, a novel CaHPO4·2H2O (DCPD) and CaCO3 composite coating with no cracks was obtained via a chemical conversion method assisted by ultrasound. DCPD coatings were also fabricated in the same method. All the coatings possess excellent adhesion strength to the substrates. In addition, electrochemical tests results show that the elimination of cracks greatly improves the anticorrosion performance of composite coatings. Optimization of the bath constituents resulted in a reduced reliance on interfacial electrochemical reactions during the co-deposition process, which plays a critical role in attaining the high-quality coating. This innovative composite coating provides a promising avenue for surface treatments of magnesium alloy concrete formwork.

Anticorrosion performance of AZ41 Mg alloy coated with three different kinds of release agents was investigated embedded in Portland cement (PC) paste containing 0.6 M NaCl. Surface characterizations were employed to obtain the surface information after coated with release agents before and after embedment. Meanwhile, electrochemical methods were adopted to assess the corrosion resistance embedded in PC paste. Results demonstrated that water-based release agent led to the corrosion of Mg alloy while the oil-based release agent not only protected the Mg alloy but also exhibited the best demolding effect. Oxide films can be generated on the surface of Mg alloy after coated with release agents. The thin film after applying the water-based release agent was magnesium/aluminium oxide and hydroxide with some talcum (3MgO & sdot;4SiO2 & sdot;H2O) particles. Additionally, thin films on the surface of Mg alloy after coated with emulsified and oil-based release agents were magnesium/ aluminium oxide and hydroxide.

An anticorrosive CaCO3-coated Mg(Al)O passive layer was obtained via the ultrasound-assisted electrodeposition on AZ41 Mg alloy for concrete formwork. Corrosion rate of the CaCO3/Mg(Al)O coated AZ41 Mg alloy was lower than 0.005 mmy  1 in Portland cement (PC) system containing 0.6 M NaCl. Ultrasound plays a dual-role in forming a dense Mg(Al)O passivation film and densifying the outer CaCO3 layer. Furthermore, re-passivation instead of corrosion was observed during the embedment, attributed to the double-layer structure effectively increasing the critical chloride ion concentration for corrosion. Formation and anticorrosion mechanism as well as the role of the passivation film in anticorrosion are discussed.

The effects of Er and Ni content on the microstructure evolution, corrosion mechanism of Mg-Er-Ni alloys with different orientations were investigated. With the increase of Er and Ni content, the corrosion rate of extrusion direction (ED) increases, while transverse direction (TD) is reversed, which may be due to the distinct corrosion mechanism in different orientations, where ED and TD exhibit soluble and corrosion-resistant mechanism, respectively. Moreover, high content second phase alloy with a large deformation grain fraction and low levels second phase alloy with fully recrystallized grains have larger and smaller corrosion rate differences in ED and TD, respectively.& COPY; 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The microstructure evolution and corrosion mechanism of Mg-9Er-xGd-2Ni alloys, subjected to Gd addition and extrusion, were investigated in this study. Results shows that with the increase in Gd content from 1.0 wt.% to 5.0 wt.%, the second phase change from continuous network LPSO phase with intragranular gMODIFIER LETTER PRIME phase to a monolithic continuous network LPSO phase, while the corresponding volume fraction of the second phase remains essentially unchanged. Moreover, it is noted that increasing Gd content contributed to a reduction in the corrosion rate of alloy by reducing galvanic corrosion couples and facilitating the formation of double Gd2O3 and Er2O3 corrosion-resistant films. Ultimately, what's most noteworthy is that compared with as-cast alloys, the corrosion rate of asextruded alloys increased by 49.2%-125.3% with increasing Gd content, which is due to the streamlined LPSO phase distribution weakening the corrosion barrier effect of highvolume fraction network distribution LPSO phase alloy and grain refinement providing more corrosion interfaces that inhibited the formation of corrosion-resistant product films. This study provides new provides new insights for the development of highly degradable Mg-Er-Gd-Ni alloys that have high strength potential for applications in unconventional oil and gas extraction. (c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND

A CaCO3 coating with good anticorrosion and self-healing performance was fabricated on the as-prepared MAO coating on the surface of AZ41 Mg alloy via ultrasound-assisted chemical conversion, a DCPD(CaHPO4·H2O) coating was also fabricated on the MAO coating as a comparison. Surface characterizations were carried out to obtain the morphology and composition of CaCO3 coating formed and electrochemical methods were adopted to assess the corrosion resistance of Mg alloy embedded in PC paste. The self-healing property of MAO/CaCO3 coating was ascribed to the formation of extra calcite. This coating may become a potential target for surface modification of magnesium alloy formwork.

A superhydrophobic anticorrosive CaCO3 coating was prepared on Mg-Nd alloy by ultrasound-assisted chemical conversion. Results show that the prepared coating consists of an outer durian-peel like CaCO3 layer and a compact inner (Ca, Mg)CO3 layer. Ultrasound treatment enhances the homogeneity and decreases the size of CaCO3 particles in coating, which contributes to its superhydrophobicity. This results in an enhanced anticorrosive property of coating via ultrasonic treatment. Ultrasound possibly accelerates the nucleation of CaCO3 crystals and assists the removal of hydrogen bubbles. A self-healing property of ultrasonically prepared coating was also obtained due to the formation of vaterite and Ca3(OH)2(CO3)2.

The effects of the high content of erbium (Er) addition (9.5-17 wt%) and short-time low-temperature heat treatment on the microstructure evolution, corrosion behaviors and mechanism of Mg-xEr-1.6Ni alloys have been investigated. After heat treatment, the corrosion rate for various Er content alloys increased by 15.1-338.8% in comparison to as-cast alloys, which was mainly related to the formation of Er-rich phases and the increase the density of laminar gamma ' phase. These phases increase the galvanic coupling pairs and provide more corrosion propagation paths, reducing the Er content in the Mg matrix and weakening the corrosion barrier.