Properties Of Mg Research Articles

In-situ formation of uniform Mg2Ni catalyst and hydrogen storage properties of Mg[sbnd]41Ni alloys with varied grain sizes and morphologies

In order to clarify the cyclic microstructure evolution process and the influence of grain size on the hydrogen de−/absorption properties of magnesium-based alloys. Mg-41 wt%Ni (Mg41Ni) alloys with varying grain sizes were prepared using different solidification rates. By analyzing the cross sections of ball-milled particles, it is found that the amorphous layer generated during ball milling is not conducive to the activation stage. Additionally, the coarse primary Mg2Ni and the lamellar Mg2Ni in the eutectic break into smaller Mg2Ni particles during the hydrogen absorption and release cycles. Thus, the fast solidified alloys can absorb 2.1 wt% of hydrogen gas at 125 °C, and complete decomposition can be achieved in 2.4 min at 300 °C. The activation energy of dehydrogenation decreases from 93.2 kJ/mol for slow solidification to 85.9 kJ/mol for fast solidification. Different kinetic models are used to fit and investigate the rate-controlling process of hydrogen desorption. The activated sample consists of the Mg matrix and uniformly distributed fine Mg2Ni particles due to the self-refinement, which significantly shortens the diffusion distance of H atoms. Besides, the multitude of pores generated inside the particles also facilitate the ingress and outflow of hydrogen.

Efficient nanocatalysis of Ni/Sc2O3@FLG for magnesium hydrolysis of hydrogen generation

Magnesium is one of the most promising candidates of light metal materials for hydrogen production by hydrolysis due to its efficient and economical properties. Various modification methods have been investigated to improve the hydrolytic properties of Mg. However, the direction of the design of efficient catalysts is unclear and needs to be guided by a richer catalytic mechanism of hydrolysis. In this work, a simple approach was used to synthesize Few Layer Graphene (FLG)-loaded ultra-fine highly dispersed Ni/Sc2O3 nanocatalyst, which achieves impressive catalytic hydrolysis results. Here, the addition of 4 wt% Ni/Sc2O3@FLG catalyst allows Mg to produce 833 mL g–1 of H2 in 20 s at 30 °C. There is an initial hydrogen release rate as high as 5942 mL g–1 min–1, a final hydrogen yield of 859 mL g–1 (99.13%), and almost complete conversion of Mg to Mg(OH)2. Furthermore, surprisingly, even with only 0.2 wt% catalysts added, Mg still has an initial hydrogen generation rate of 3627 mL g–1 min–1, which is over 20 times faster than that of Mg. It also produces 690 mL g–1 of H2 in 30 s at 30 °C. Hydrolysis kinetic curves and microscopic morphology tests show that FLG could shape and hold Mg into thin sheets, giving them an ultra-high hydrolysis rate and conversion rate. The formation of micro-galvanic cells between Ni and Mg accelerates the electrochemical corrosion of Mg and greatly enhances electron transfer during hydrolysis. This work provides a new strategy for the preparation of efficient nanocatalysts, which is expected to make “Mg-efficient catalyst” the most ideal light metal-based material for hydrogen production by hydrolysis.

Twin-boundary and precipitate interaction in Mg–Al alloy: an MD study

Strengthening of Mg-alloys by precipitation is much less efficient than in other metallic alloys (e.g. Al) as the Mg17Al12 precipitates grow as thin plate or lozenge shaped or long rod shape parallel to the basal plane. Recently atomistic simulations reveal that the dislocation-precipitate interaction is very week to claim for the precipitation hardening mechanism. However, the interaction of twin-boundary with the Mg17Al12 precipitate remains unexplored using atomistic simulation. In the present study we focus on the twin-boundary/precipitate interaction at different temperatures, precipitate sizes and varied applied loads, carried out using classical molecular dynamics methodology. In particular, the activation energies necessary to overcome various precipitates are determined as a function of the temperature, precipitate size and applied load. The velocity profile of the twin is calibrated with these different external conditions. An attractive nature of interaction has been observed while the twin-boundary comes closer to the precipitate and a network of dislocations are observed when the twin-boundary bypass the precipitate, as manifested through our atomistic microstructures. These results provide valuable information about the precipitate hardening mechanisms and suggested new avenues to improve the mechanical properties of Mg–Al alloys.

Achieving high strength near 400 MPa in an ultra-fine grained Mg–Bi–Ca ternary alloy via low-temperature extrusion

Significantly enhancing the mechanical properties of Mg–Bi base series alloys is of great significance for their wider application prospects. Here, a new Mg–3Bi–1Ca (BX31, wt.%) alloy showing high tensile yield strength of ∼397.1 MPa, high ultimate tensile strength of ∼416.2 MPa and acceptable elongation of ∼8% was fabricated by low-temperature extrusion. The analysis of microstructure showed that the enhanced yield strength was attributed to the ultra-fine grain structure (∼0.84 μm), nano-scale second phases including Mg2Bi2Ca and Mg2Ca, and Ca segregation at grain boundaries. In addition, a weak basal fiber texture to some extent provided more basal slip activities, guaranteeing the suitable ductility. The dynamic recrystallization and dislocation behavior of the BX31 billet during extrusion were also systematically observed and discussed to reveal the formation mechanisms of the ultra-fine grain structure with the weak basal fiber texture in the as-extruded BX31 alloy. As mentioned above, this work offers a new insight to obtain high-performance Mg–Bi base series alloys.

Comparison of the antibacterial properties of Mg, Mg-2Ag, and Ti intramedullary implants in a murine model of Staphylococcus aureus bacteremia -related periprosthetic osteomyelitis

Knowledge on the susceptibility of novel biomaterials to potential challenges in clinical practice is critical to defining the scope of implementation and further improvement of candidate materials. While periprosthetic infections remain a major and most difficult to treat complication in implantation orthopedics, magnesium-based biodegradable alloys are currently under eager attention as alternatives. Many in vitro studies reported profound antibacterial potential of pure magnesium and its alloys with improved bactericidal features. Some animal models with direct inoculation of bacteria or implantation of infected implants confirmed these results in vivo. However, the susceptibility of magnesium and binary alloys of magnesium and silver has not previously been assessed in experimental settings for hematogenous periprosthetic osteomyelitis. In the present study, we compared the antibacterial activity of pure Mg and Mg-2Ag with that of medical grade Titanium using a murine model for Staphylococcus aureus bacteremia –related peri-implant bone infection. The bacteria colonization was inhibited on surfaces of Mg and Mg-2Ag intramedullary implants. However, the bacteria load in surrounding tissue was found to be similar between the three materials. Current findings (i) indicate that biocidal efficacy of a material in vivo can be influenced by contamination route; (ii) aware of a limited antibacterial potential of unmodified magnesium and magnesium-silver implants for patients with elevated risks of bloodstream infections; and (iii) emphasize the need of further improvements/alloy modifications for particular clinical purposes.

Effect of extrusion temperatures on the microstructure, texture, and mechanical properties of Mg–5Sn–1Si–0.6Ca alloy

In this paper, the effect of extrusion temperatures (250 °C, 300 °C and 350 °C) on the microstructure, second phases particle, texture, and mechanical properties of the Mg–5Sn–1Si–0.6Ca alloy were discussed. The results show that after extrusion the second phases in the alloy were broken and distributed along the grain boundary. Decreasing the extrusion temperature is beneficial to dynamic precipitation and grain refinement. During the extrusion process, a large number of Mg2Sn nanoprecipitates are dynamically precipitated from the Mg matrix and their number increased and their size decreased with the decrease of extrusion temperature. The grain size was refined from 5.8 μm to 3.328 μm with the extrusion temperature decreasing from 350 °C to 250 °C. Besides, the texture intensity was also reduced with the decrease in extrusion temperature. The strength and plasticity of the Mg–Sn–Si–Ca alloys are simultaneously improved by the method of “solid solution + low-temperature extrusion”. When the extrusion temperature is 250 °C, the alloy obtains superior engineering mechanical properties with the yield strength of 287 MPa, ultimate tensile strength of 343 MPa and elongation to failure of 23.3%. The high strength is mainly attributed to the combined effect of grain size, weak texture, and high density of precipitation. The good ductility is mainly attributed to the grain refinement and high Schmid factors of basal slip.

Structure‐Induced Enhanced Dissolving Properties of Mg(OH)2 Prepared by Glycine‐Assisted MgO Hydration (Crystal Research and Technology 8/2023)

Structure‐Induced Enhanced Dissolving Properties of Mg(OH)₂ Prepared by Glycine‐Assisted MgO Hydration (Crystal Research and Technology 8/2023)

Deformation behaviors and the related high-temperature mechanical properties of Mg–11Gd–5Y–2Zn–0.7Zr via regulating extrusion temperatures

The effects of extrusion temperatures (430, 450, 470 and 490 °C) on the microstructures and mechanical properties of Mg–11Gd–5Y–2Zn–0.7Zr (GW) alloys at room temperature (RT), 250, 300, 350 °C were systematically investigated. The dynamic precipitation of blocky and lamellar long period stacking ordered (LPSO) phases was taken place during hot extrusion. The dominant texture changed from <10 1¯0 >//ED to <0001>//ED with increasing extrusion temperature. Tensile results indicated that the GW alloy extruded at 430 °C (GW430) exhibited the highest mechanical properties at both RT and elevated temperatures, which was ascribed to the fine dynamic recrystallized (DRXed) grains, un-DRXed grains with an orientation of <10 1¯0 >//ED, and the LPSO phase strengthening. When tensile tested below 300 °C, slips on the blocky LPSO phase and kinks of lamellar LPSO phase were the primary deformation modes, followed by grain boundary crack. At 350 °C, grain boundaries became the vulnerable sites to be activated. For GW alloys extruded at 450, 470 and 490 °C, an abnormal increase of mechanical properties was observed at 300 °C. This was due to the occurrence of multiple-slip, which showed the intersection and entanglement of dislocations and thus improving the strength of Mg matrix.

Correction to: Improving the Mechanical Properties of Mg–Gd–Y–Ag–Zr Alloy via Pre‑Strain and Two‑Stage Ageing

Correction to: Improving the Mechanical Properties of Mg–Gd–Y–Ag–Zr Alloy via Pre‑Strain and Two‑Stage Ageing

Diffusion behaviors and mechanical properties of binary Mg–Ce system

In this work, the solid-solid diffusion reaction and growth kinetics of the Mg–Ce system was investigated by diffusion coupling technique. Four intermetallic compounds Mg12Ce, Mg41Ce5, Mg3Ce, MgCe and one solid solution phase δCe were observed in the diffusion zone with the annealing temperature range of 673–823 K. The results shown that the growth process in the diffusion area was dominated by bulk diffusion. The growth constants, integrated diffusion coefficients, growth activation energies and diffusion activation energies of the four intermetallics were calculated based on the thickness of the phases, reaction temperature and annealing time. Mg3Ce has the largest diffusion activation energy. The mechanical properties of the four IMCs were investigated by using nanoindentation characterization technology and first-principles calculations. The nanoindentation tests show that the Mg12Ce phase possessed the largest Young's modulus (66.08 GPa) and hardness (2.14 GPa). The experimental results are consistent with the trend of the calculated results. The obtained diffusion kinetical properties and mechanical properties of the Mg–Ce system provide useful data for the development of new magnesium-rare earth alloys.

Synergistic effect of multi-element co-segregation on mechanical properties of Mg twin grain boundary

Properties of grain boundaries (GBs) are pronouncedly influenced by alien elemental segregation. Synergistic effect of co-segregation behavior on mechanical properties of Mg twin GB was systematically investigated with first-principles calculations. Ten elements (Ni, Mn, Zn, Al, Ag, Ti, Li, Zr, Y, Ca) for single segregation and four solute combinations (Al–Ca, Al–Y, Zn–Ca, Zn–Y) for co-segregation were chosen respectively, the segregation energies and solubility energies with different elemental concentrations were calculated to evaluate the thermodynamic stability of corresponding segregated GBs. These solute atoms have unique effects on the stability of the system, and the interaction between solute atoms also has a synergistic effect on the stability of the system. It is found that the segregation tendency is enhanced and the GB structure tends to be stable with the increase of the concentration of solute atoms at the appropriate sites, regardless of single-element segregation or co-segregation. The redistribution of GB charges due to co-segregation significantly affects the binding and mechanical properties of GBs. With the increase of the co-segregation concentration, the lamellar charge is transferred between the matrix and the twins, which further enhances the electron hybridization and leads to a notable enhancement of interface binding. This shows that the appropriate combination of solute elements can effectively improve the mechanical properties of the interface. The manuscript reveals the theoretical understanding of the effect of elemental segregation on the mechanical properties of GB, and provides design ideas for the tuning of mechanical properties of magnesium alloy by GB engineering.

Effect of extrusion temperature on microstructure and tensile properties of Mg–Gd–Er–Zn–Zr alloy containing LPSO phase

Effect of extrusion temperature on microstructure and tensile properties of Mg–Gd–Er–Zn–Zr alloy containing LPSO phase

Structural and Thermodynamic Properties of Magnesium-Rich Liquids at Ultrahigh Pressure

We explore the structural properties of Mg, MgO, and MgSiO3 liquids from ab initio computer simulations at conditions that are relevant for the interiors of giant planets, stars, shock compression measurements, and inertial confinement fusion experiments. Using path-integral Monte Carlo and density functional theory molecular dynamics, we derive the equation of state of magnesium-rich liquids in the regime of condensed and warm dense matter, with densities ranging from 0.32 to 86.11 g cm−3 and temperatures from 20,000 K to 5 × 108 K. We study the electronic structure of magnesium as a function of density and temperature and the correlations of the atomic motion, finding an unexpected local maximum in the pair correlation functions that emerges at high densities which decreases the coordination number of elemental magnesium and reveals a higher packing. This phenomenon is not observed in other magnesium liquids, which maintain a rather constant coordination number.

Effects of Ca addition on the microstructure and mechanical properties of Mg–Zn–Sn–Mn alloys

The effects of Ca addition on the microstructure and mechanical properties of Mg–Zn–Sn–Mn alloys were investigated in this study. The Mg–6Zn–4Sn–1Mn–xCa (x = 0, 0.2, 0.5, 1 and 2 wt%) alloys consist of the α-Mg, Mg2Sn, Mg7Zn3, MgZn, α-Mn, CaMgSn, MgZn2, Mg2Ca and Ca2Mg6Zn3 phases. With increasing Ca content, the eutectic phase and grains were refined, and the morphologies of the CaMgSn phases changed from point-like to needle-like, rod-like and lath-like. At room temperature, small amounts of Ca can improve properties owing to refinement strengthening. The two-stage aged Mg–6Zn–4Sn–1Mn–0.2Ca alloy has the best comprehensive properties at room temperature, with an ultimate tensile strength (UTS), yield strength (YS) and elongation of 407 MPa, 392 MPa and 6.2%, respectively. When the Ca content increased, the number of CaMgSn phases increased, and the morphologies coarsened. Further, it was a brittle phase, resulting in the deterioration of alloy properties. At high temperatures, a small amount of Ca can improve the high-temperature plasticity. The elongations of the as-extruded Mg–6Zn–4Sn–1Mn–0.2Ca alloy were 76.9% (150 °C) and 133.8% (200 °C). A high Ca concentration can significantly improve the high-temperature strengths because of the good thermal stability of the CaMgSn phases, the best UTS and YS are 160 MPa and 136 MPa, respectively, in as-extruded Mg–6Zn–4Sn–1Mn–2Ca alloy at 150 °C.

Structure‐Induced Enhanced Dissolving Properties of Mg(OH)2 Prepared by Glycine‐Assisted MgO Hydration

AbstractMg(OH)2’s dissolving properties have a considerable influence on its application performance. This study aims to improve the dissolving properties of Mg(OH)2 by modifying its crystal structure. Mg(OH)2 crystals with a large diameter‐to‐height ratio (≈40) structure are synthesized via a glycine‐assisted MgO hydration method utilizing glycine's differing adsorption energy on the (001) and (110) surfaces of Mg(OH)2 (−306.2 and −277.4 kJ mol−1). Compared to the control sample, the results of the dissolution kinetics investigation indicate that glycine‐assisted hydration considerably improves the apparent reaction rate constant of dissolution from 0.0020–0.0071 to 0.0039–0.0120 min−1. The enhanced dissolving properties are mostly induced by the large and thin crystal grain structure, which disintegrates easily during the dissolution process, exposing more reactive sites. The findings reported in this study provide a new approach to improving the dissolving properties of Mg(OH)2 that can enable its enhanced use in various applications.

Insights on Elastic Anisotropy and Thermal Properties of Mg–Ti–O Compounds from First‐Principles Calculations

First‐principles calculations are employed to explore the elastic anisotropy and thermal properties of Mg–Ti–O compounds (MgTiO3, MgTi2O5, and Mg2TiO4). The structure parameters used in this work are in good agreement with other theoretical and experimental results. The mechanical stability and ductile nature are demonstrated. The elastic anisotropy is characterized by different anisotropy indexes, three‐dimensional (3D) surface constructions, and two‐dimensional (2D) projections of Young's modulus. Besides, the sound velocities, Debye temperature, and minimum thermal conductivity are also investigated from the elastic modulus. The obtained results can provide references for future experimental investigations and engineering applications of these Mg–Ti–O compounds.

A comparative study of the role of Zn in microstructures and the mechanical properties of Mg–Gd–Y–Zr alloys

The microstructures and mechanical properties of Mg–8.5Gd–4.5Y–0.3Zr (wt.%) alloys with and without Zn addition were investigated in this study, and the strengthening mechanisms of these two alloys were also discussed. The results show that the as-extruded alloys possesses a fine and uniform microstructure, while the as-extruded alloy with Zn addition has finer grains due to the dislocation motion inhibited by the long-period stacking ordered (LPSO) phase. Dynamic precipitation occurs during the extrusion process and unevenly distributes in both alloys, which is beneficial for the grain refinement. The yield strength and elongation of the peak-aged alloy with Zn addition are about 56 MPa and 2 times higher than that of the alloy without Zn addition; this higher elongation and yield strength can be mainly ascribed to the LPSO and γ′ phases strengthening.

Antibacterial PLA/Mg composite with enhanced mechanical and biological performance for biodegradable orthopedic implants

Biodegradability, bone-healing rate, and prevention of bacterial infection are critical factors for orthopedic implants. Polylactic acid (PLA) is a good candidate biodegradable material; however, it has insufficient mechanical strength and bioactivity for orthopedic implants. Magnesium (Mg), has good bioactivity, biodegradability, and sufficient mechanical properties, similar to that of bone. Moreover, Mg has an inherent antibacterial property via a photothermal effect, which generates localized heat, thus preventing bacterial infection. Therefore, Mg is a good candidate material for PLA composites, to improve their mechanical and biological performance and add an antibacterial property. Herein, we fabricated an antibacterial PLA/Mg composite for enhanced mechanical and biological performance with an antibacterial property for application as biodegradable orthopedic implants. The composite was fabricated with 15 and 30 vol% of Mg homogeneously dispersed in PLA without the generation of a defect using a high-shear mixer. The composites exhibited an enhanced compressive strength of 107.3 and 93.2 MPa, and stiffness of 2.3 and 2.5 GPa, respectively, compared with those of pure PLA which were 68.8 MPa and 1.6 GPa, respectively. Moreover, the PLA/Mg composite at 15 vol% Mg exhibited significant improvement of biological performance in terms of enhanced initial cell attachment and cell proliferation, whereas the composite at 30 vol% Mg showed deteriorated cell proliferation and differentiation because of the rapid degradation of the Mg particles. In turn, the PLA/Mg composites exerted an antibacterial effect based on the inherent antibacterial property of Mg as well as the photothermal effect induced by near-infrared (NIR) treatment, which can minimize infection after implantation surgery. Therefore, antibacterial PLA/Mg composites with enhanced mechanical and biological performance may be a candidate material with great potential for biodegradable orthopedic implants.

Antibacterial and biocompatible Zn and Cu containing CaP magnetron coatings for MgCa alloy functionalization

The application of bioresorbable magnesium-based alloys in medical implants has been limited by their rapid dissolution rate. In order to enhance their suitability for medical use, this study proposes the deposition of calcium phosphate (CaP) onto Mg (0.8) Ca alloy using an RF magnetron sputtering with stoichiometric hydroxyapatite and Zn- or Cu-substituted hydroxyapatites. The comparison study assessed structure, composition, and mechanical properties of Mg (0.8) Ca alloy, Zn, and Cu containing CaP coatings. CaP coatings showed an increased Ca/P ratio due to re-sputtering. Sputtering of Zn- and Cu-substituted hydroxyapatites resulted in CaP dopant concentrations of 0.6 ± 0.2 wt% and 0.4 ± 0.1 wt%, respectively. All deposited coatings were found to be amorphous. Addition of Cu or Zn dopant slightly changed the CaP coatings' scratch resistance, with critical loads of 2.19 ± 0.60 N, 2.55 ± 0.95 N, and 2.76 ± 1.29 N for CaP, Zn–CaP, and Cu–CaP coatings, respectively. CaP coatings reduced corrosion current and increased electrical resistance compared to MgCa samples, but Cu addition accelerated corrosion. Biological tests revealed that the hAMSCs survival was improved and the bacteriostatic effect on the pathogenic SA strain was enhanced for Zn–CaP coatings when compared to CaP and Cu–CaP coatings. These findings suggest that the deposition of CaP coatings onto Mg (0.8) Ca alloy, and particularly the use of Zn-substituted hydroxyapatites, could be a promising approach to enhance the suitability of magnesium-based alloys for medical implant applications.

Evaluation of microstructure and tensile properties of Mg–5Zn-xZr-yCa alloys

In this work, an attempt was made to study the synergetic effects of changes in alloying elements including Zr and Ca, as well as the hot extrusion process on the microstructure, texture, and mechanical properties of Mg–Zn-xZr-yCa (x= 0.2 and 0.8 wt %; and 0<y<2) alloy. To do so, a variety of tests (OM, SEM, EBSD, EDS, TEM, APT, hardness and tensile tests) were performed after sample preparation. It was shown that Ca/Zr ratio plays an essential role in modifying the microstructure and mechanical properties of the alloy. For Ca/Zr<1, the grains size was remarkably refined to 1.2 μm, the wrought texture was moderately weakened, and the mechanical properties were significantly increased to 429 MPa. However, for Ca/Zr>1 grain size was almost unchanged, the texture of hot-extruded alloys became more equiaxed after hot extrusion, and tensile strength decreased compared to with Ca/Zr=1. Microstructural analysis revealed that Zr-bearing phases (Zn22Zr and Zn39Zr5) and solute theory were the dominant mechanisms of grain refinement in the as-cast state. An atom probe tomography technique was utilized to assess the segregation of solute elements into the grain boundaries. It was shown that particle stimulated nucleation is not likely to be the main mechanism of texture weakening of extruded alloys; and the solute segregation into grain boundaries facilitates this phenomenon. Finally, it was seen that values of yield and ultimate tensile strengths of Mg–5Zn-0.8Zr-0.5Ca were 372 and 429 MPa, respectively.