Pure Magnesium Research Articles

Dramatically Improved Strength and Plasticity of Pure Magnesium Through Multi-Microalloying with Al, Ca, Mn, Zn, and Sn Elements

Dramatically Improved Strength and Plasticity of Pure Magnesium Through Multi-Microalloying with Al, Ca, Mn, Zn, and Sn Elements

Cavitation behavior during tensile deformation at room temperature in fine-grained pure magnesium

Cavitation behavior associated with grain boundary sliding at room temperature was investigated using fine-grained magnesium (Mg) specimens produced by extrusion or high-pressure torsion. Regardless of the process method, flow stress in both of Mg specimens depended on the tensile strain rate, and the strain rate sensitivities (m-values) were determined to be approximately 0.3 at low strain rates. Deformed microstructural observations revealed that many cavities were formed at grain boundaries and grain boundary triple junctions, even during the plastic deformation at room temperature. The size and density of such cavities increased with the progression of deformation. The majority of cavities were controlled by plasticity, and the cavity growth rate was similar to those typically observed in superplastic Mg alloys subjected to elevated temperature tensile tests. In addition, initial basal texture was unlikely to affect these cavitation behaviors, e.g., cavity growth rate.

Effect of Laser Surface Texturing parameters on the texture formation in pure magnesium substrate

Magnesium and its alloys find a prominent application in bio-implant applications. However, their poor surface property like high corrosion rate has limited their wide usage. Various conversion and deposited coating methods are available to protect the magnesium surface from the rapid degradation. Recently, laser surface texturing (LST) has been identified as a unique surface treatment technique. In this work, LST experiments were conducted on a pure magnesium substrate with a picosecond laser system. The effect of laser scan speed and number of passes on the texture formation and surface roughness was investigated. Microstructure of the textures was investigated through scanning electron microscopy and surface roughness was investigated through White Light Interferometry (WLI). Results revealed that texture formation is accurate in lower laser scanning speed. Moreover, depth of the textures increases in lower scanning speed conditions. Surface roughness of the textures is governed by the formation of recast materials in and around the textures.

Tribological Behavior of Mg/Fe3O4 Recycled Nanocomposites Processed Through Turning Induced Deformation Technique

Abstract Magnesium nanocomposites with improved mechanical and tribological properties have attracted widespread interest in the automotive sector. Given the great potential of magnesium nanocomposites in the automotive sector and the need for recycling materials to minimize their negative impact on the environment, it is imperative to consider the possibility of a practical approach to recycling these materials. In this study, turning induced deformation (TID) technique is used to recycle the magnesium composites containing iron oxide (Fe3O4) nanoparticles. The chips collected from the turning process of composites were cold compacted and hot extruded into cylindrical rods. The extruded materials were investigated for their tribological response under dry sliding conditions. The wear tests were performed using a pin on disc tribometer against an EN31 alloy steel counter disc under applied loads of 10, 20, 30, and 50 N and sliding speeds of 1, 2, 3, and 5 m/s. The worn pin surfaces were examined under scanning electron microscopy integrated with an energy dispersive x-ray spectrometer to understand wear characteristics. The results revealed a better wear resistance and friction coefficient for recycled nanocomposites than pure magnesium. The enhanced wear resistance of recycled nanocomposites is attributed to the increased hardness and strength due to the Fe3O4 nanoparticles and the turning induced deformation process. The wear surfaces revealed abrasion and delamination as the predominant wear mechanism, with thermal softening occurring only at the highest applied load and sliding speed.

Significance of Alloying Elements on the Mechanical Characteristics of Mg-Based Materials for Biomedical Applications

Magnesium alloys are widely employed in various applications due to their high strength-to-weight ratio and superior mechanical properties as compared to unalloyed Magnesium. Alloying is considered an important way to enhance the strength of the metal matrix composite but it significantly influences the damping property of pure magnesium, while controlling the rate of corrosion for Mg-based material remains critical in the biological environment. Therefore, it is essential to reinforce the magnesium alloy with a suitable alloying element that improves the mechanical characteristics and resistance to corrosion of Mg-based material. Biocompatibility, biodegradability, lower stress shielding effect, bio-activeness, and non-toxicity are the important parameters for biomedical applications other than mechanical and corrosion properties. The development of various surface modifications is also considered a suitable approach to control the degradation rate of Mg-based materials, making lightweight Mg-based materials highly suitable for biomedical implants. This review article discusses the various binary and ternary Mg alloys, which are mostly composed of Al, Ca, Zn, Mn, and rare earth (RE) elements as well as various non-toxic elements which are Si, Bi, Ag, Ca, Zr, Zn, Mn, Sr, Li, Sn, etc. The effects of these alloying elements on the microstructure, the mechanical characteristics, and the corrosion properties of Mg-based materials were analyzed. The mechanical and corrosion behavior of Mg-based materials depends upon the percentage of elements and the number of alloying elements used in Mg. The outcomes suggested that ZEK100, WE43, and EW62 (Mg-6% Nd-2% Y-0.5% Zr) alloys are effectively used for biomedical applications, having preferable biodegradable, biocompatible, bioactive implant materials with a lower corrosion rate.

Plasticity enhancement in pure magnesium achieved based on initial twin orientation regulation

In the short communication, the ductility of pure magnesium was enhanced about 3 times at room temperature compared with the initial material based on the proposed concept of shear strain-induced twin orientation regulation (SITOR). The initial tension twin orientation inclines about 30° to the TD-ND plane which is regulated by the introduced shear deformation so that a larger Schmid factor of basal slip is achieved. Due to the promotion of basal slip, the plasticity of pure Mg is improved obviously.

On the structure-properties relationship of amorphous and crystalline silica nanoparticles reinforced magnesium matrix nanocomposites

In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.

Mechanisms of Cracking in Pure Magnesium During High Strain Rate Plastic Deformation

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Study on fretting wear properties of medical Mg-2.0Zn-1.6Ca alloy

Due to its good biocompatibility and biomechanics, magnesium alloy has made great progress in the application of absorbable and implantable biomedical materials in recent years. At the same time, the disadvantages of magnesium alloy materials are more obvious. Because of its poor wear resistance, magnesium alloy is easy to fret with human bones after being implanted as a bone plate, resulting in wear pits and failure. In this paper, magnesium alloy was prepared, calcium and zinc elements were added into pure magnesium according to a certain proportion, and then the magnesium alloy with excellent performance was formed by solid solution treatment and extrusion strengthening. After that, fretting friction type, friction coefficient and wear pits were studied by fretting wear test. The results show that with the decrease of extrusion temperature, the surface hardness increases and the friction coefficient decreases, which is very beneficial to improve the wear resistance of the workpiece. The purpose of this paper is to improve the fretting wear performance of magnesium alloys, and to provide theoretical and practical guidance for the preparation, processing and application of high-performance medical magnesium alloys.

(Digital Presentation) Enhanced Electrochemical Phosphate Recovery from Wastewater: Implications of Pulsating Anode Potential

Electrochemical recovery of phosphorus (P) as struvite (or magnesium ammonium phosphate hexahydrate, MgNH4PO4.6H2O) fertilizer using a sacrificial pure magnesium (Mg) anode is considered a sustainable strategy to deal with the limited availability of rock phosphate. However, the formation of an electrically passive film of magnesium hydroxide (Mg(OH)2) and/or struvite on the surface of Mg upon immediate immersion in aqueous phosphate solution limits the release of divalent Mg ions and decreases struvite precipitation. The present work highlights struvite recovery by an electrochemical method upon application of a dynamic voltage with a sinusoidal waveform. Our results demonstrate that a dynamic potential, when compared to a constant potential, can enhance the rupture of the passivating film, and facilitate the release of Mg2+ from the metal thereby overcoming the problems related to electrical passivation.Aqueous solutions of ammonium dihydrogen phosphate (NH4H2PO4, 10 mM) at neutral pH were used as test solutions. Mg2+ release was notably increased by ~48% relative to constant voltage applications, which subsequently led to ~20% higher phosphate recovery. Characterization studies including X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the presence of struvite in the recovered precipitate. Surface characterization of electrodes using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) also confirms a higher extent of passivating film breakdown in the presence of dynamic voltage.

Assessment of the corrosion behaviour of untreated and chemically treated pure magnesium in simulated body fluid

The corrosion behaviour of pure Mg in simulated body fluid (SBF) and the effect of chemical treatment on the corrosion resistance property were investigated using DEIS (dynamic electrochemical impedance spectroscopy), EIS (electrochemical impedance spectroscopy), PDP (potentiodynamic polarization), SEM (scanning electron microscopy), AFM (atomic force microscope), and pH measurement techniques for 30 h. NaOH or H2O2 were utilized for the chemical treatment. The DEIS was used for the first time in the investigation of Mg corrosion in SBF. Results obtained disclosed that the chemical treatment benefitted the anticorrosion property immensely. Results from both the electrochemical and surface analysis techniques are consistent.

Visualizing dynamic evolution of electrode/electrolyte interface via model-free analysis of in-situ spectroscopic ellipsometry

Spectroscopic ellipsometry is a promising technique for realizing in-situ study of electrode/electrolyte interface (EEI) owing to its high-sensitive and non-destructive advantages. However, difficulties in modelling complex systems and analysing massive data of in-situ tests hinder its widespread applications. Herein, a model-free method was established and a featured parameter named interfacial evolution rate (IER) was proposed to qualitatively and quantitatively probe the dynamic evolution rate of EEI. The in-situ electrochemistry-spectroscopic ellipsometry measurement of pure magnesium corrosion in 5 wt.% NaCl solution before and after adding Na2SiO3·9H2O inhibitor (0.001 mol L−1) was conducted to verify the utility of the established method. Without the inhibitor, IER exponentially decreases from 12 to 3 and lasts for about 60 min, indicating the gradual stabilization of the interface. The subsequent increase of IER suggests the accelerated dynamic evolution of EEI. In the presence of the inhibitor, IER decreases from 0.5 to 0.3 and remains stable for 230 min, corresponding to the significant corrosion inhibition of sodium silicate. Ex-situ SEM, EDS, Raman and XPS characterizations of the corrosion products were also performed to support the analysis. The model-free analysis method of spectroscopic ellipsometry established in this work shows potential applications in the in-situ investigations of various complex systems.

Effect of sodium‐zinc EDTA and sodium gluconate as electrolyte additives on corrosion and discharge behavior of Mg as anode for air battery

AbstractThe corrosion inhibiting performance of EDTA‐ZnNa2 and C6H11NaO7 for pure magnesium in a 3.5 wt% NaCl electrolyte was investigated through electrochemical tests and surface microanalysis. And their effect on discharge behavior of Mg anode used for air battery was evaluated through constant‐current discharging tests. The inhibition performance varied with different additive concentrations and the maximum inhibition efficiency values were obtained as 87.11% and 77.70% by using 0.005 M EDTA‐ZnNa2 and 0.01 M C6H11NaO7, respectively. Both the presence of 0.005 M EDTA‐ZnNa2 and 0.01 M C6H11NaO7 in electrolyte improved the battery performance, especially under a smaller discharging current. The discharge platform time was extended from 15.66 to 22.57 h and 20.04 h by adding EDTA‐ZnNa2 and C6H11NaO7 at discharging current density of 2 mA cm−2 respectively, accompanied by a negligible battery voltage drop of about 20 mV. In the case of EDTA‐ZnNa2, zinc hydroxide formed by the dissociated zinc ions cooperated with magnesium hydroxide and organic adsorption film for corrosion inhibition. Therefore, by using it a more pronounced discharge performance was achieved than C6H11NaO7.

Assessing Mg/Si3N4 biodegradable nanocomposites for osteosynthesis implants with a focus on microstructural, mechanical, in vitro corrosion and bioactivity aspects

Magnesium-based biodegradable implant materials for the osteosynthesis process (fixation or stabilizing of a fractured bone) are on the verge of being used clinically. However, the rapid degradation of magnesium-based materials in the physiological environment results in a loss of mechanical integrity before the complete healing of the fracture site. To address this issue, the present study used Silicon Nitride (Si3N4) nanoparticles to improve the in-vitro degradation resistance along with the mechanical strength and ductility of Magnesium. The Si3N4 nanoparticles were homogeneously reinforced in the pure Magnesium matrix through the ultrasonic-assisted stir casting method. Moreover, the effect of Si3N4 nanoparticles on microstructure, mechanical, in-vitro corrosion and bioactivity response of Mg/Si3N4 nanocomposites was studied. Notably, the inclusion of 1.0 vol% Si3N4 nanoparticles increased tensile strength by 1.4 times and ductility by two times. In addition, the elastic modulus of Mg/Si3N4 nanocomposites is within the range of local cortical bone elastic modulus. In-vitro immersion experiments in simulated physiological fluids revealed a 2.2-fold reduction in degradation rate compared to pure Magnesium. Moreover, the addition of Si3N4 nanoparticles enhanced the in-vitro bioactivity, as the surface of the nanocomposites showed a high needle-like Ca–P apatite layer with a 1.41 Ca/P ratio of the deposited layer close to hydroxyapatite's Ca/P ratio (1.64). Overall, this study provides the basis for the fabrication of stable yet completely biodegradable Mg/Si3N4 nanocomposite bone implants for the osteosynthesis process.

Effect of grain size on the mechanical properties and bio-corrosion resistance of pure magnesium

In addition to grain size, the mechanical properties and corrosion resistance of magnesium alloys depend on other factors such as texture, distribution of alloying elements, and homogeneity of the microstructure. These attributes might change during grain refining processes, making the situation more complex and masking the real effect of grain size. Accordingly, in the present work, the grain size of commercially pure (CP) Mg was adjusted by grain growth annealing after casting and deformation by hot rolling (for grain refinement via dynamic recrystallization during thermomechanical processing) to investigate the effect of grain size on tensile properties, hardness, and bio-corrosion resistance in simulated body fluid (SBF) for biomedical implant applications. The grain growth kinetics of commercially pure Mg was studied, where the grain growth activation energy (Q) was found to be consistent with that of the grain boundary diffusion in Mg. Based on the Hall–Petch plots, it was revealed that the yield stress (YS), ultimate tensile strength (UTS), and hardness of pure Mg are highly sensitive to average grain size in comparison to common Mg alloys. Moreover, based on the polarization curves and Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) analysis, grain coarsening led to the enhanced corrosion resistance due to the decreased grain boundary regions, where a simple linear formula was obtained for correlating corrosion current density to average grain size.

High cycle fatigue behavior of bimetallic Al 7025/CP-Mg rods produced by rotary swaging

This study aims to investigate the monotonic uniaxial tensile/compressive properties and the high cycle fatigue behavior of aluminum alloy 7025 (Al 7025)/commercially pure magnesium (CP–Mg) bimetallic rods produced via rotary swaging method at ambient temperature. In these lightweight bimetallic rods, the outer layer of aluminum can protect the magnesium core from corrosion and improve the rods' mechanical properties. The microhardness and microstructure were studied in the cross-section of the rods to investigate the manufacturing process effects on the starting materials. Based on the obtained results, under the compressive loading, the ultimate strength of the Al/Mg sample increased by 34% compared with the pure magnesium sample. Furthermore, while only 31% of the bimetallic cross-section is composed of aluminum, the tensile and compressive yield strengths of Al/Mg specimens are closer to those of the aluminum specimens. Microhardness results and the microstructural evaluation indicate that no significant chemical interface is formed between the layers. According to the fatigue test results, adding the outer layer of aluminum can increase the fatigue life more than ten times, compared with the monolithic magnesium specimens. The aluminum layer acts as a deterrent agent, delaying crack initiation and causing such substantial life improvement. The aluminum layer plays a more significant role at the lower stress levels, where most of the fatigue life is spent on crack initiation. Based on the finite element analysis, compared to the monolithic magnesium specimen at the same position, adding an aluminum layer around the magnesium core causes a 46.8% reduction in the maximum stress at the surface of the magnesium core in the bimetallic specimen. The fractography shows that the cracks initiated at the surface and propagated through the aluminum sleeve are barricaded by Al/Mg interface, resulting in new crack initiation sites on the magnesium core.

Microstructure, Mechanical and Ignition Characteristics of Si3N4 Reinforced Magnesium Matrix Nanocomposites

Lightweight magnesium-based materials have received attention in the automobile sector as a solution to minimize fuel consumption and greenhouse gas emissions. Magnesium has great weight-reduction potential in the aerospace sector, but its low ignition temperature limits its utilization. Improving magnesium’s ignition resistance is critical for aerospace applications. The present study developed Mg/Si3N4 nanocomposites to improve the ignition resistance to address this limitation. The nanocomposites were prepared by ultrasonically-assisted stir casting with 0.5, 1, and 1.5 vol% Si3N4 nanoparticles. The effect of Si3N4 nanoparticles on the ignition and compression characteristics was examined. SEM micrographs showed the homogeneous dispersion of Si3N4 nanoparticles with negligible clustering. Notably, the nanocomposites’ ignition resistance was increased by increasing the vol% of the Si3N4 nanoparticles. Adding 1.5 vol% Si3N4 nanoparticles resulted in the highest ignition temperature of 614 °C, 34 °C higher than pure magnesium. Similarly, the compressive properties were enhanced with the progressive addition of Si3N4 nanoparticles. The inclusion of 1.5 vol% Si3N4 nanoparticles resulted in a maximum compressive yield strength of 118 MPa and ultimate compressive strength of 323 MPa.

Effect of Magnesium Powder Application on the Microstructure and Properties of Rods Extruded by the Forward-Backward Rotating Die Extrusion Method.

The effects of severe plastic deformation (SPD) with a forward-backward rotating die (KOBO extrusion) on pure magnesium, in the form of cold-compacted powder, sintered powder, or cast ingots as reference, were examined. This method is known to reinforce metals, but the role of the initial form of magnesium applied in the fabrication of metal-based rods, as well as related phenomena, has not been characterized until now. The problem is important in the potential processing of commercial metal powders, the recycling of metal shavings, and the fabrication of metal matrix composites with discontinuous reinforcing phases. In the presented experiments, rods of 8 mm in diameter and 400 mm in length were obtained, and the structural effects induced by KOBO that occurred on a macro- and microscale on the surface and cross sections were characterized. Changes in the size and orientation of α-Mg crystallites were determined by XRD. The porosity, hardness, tensile strength, and compressive strength were measured, and the mechanisms of decohesion dependent on starting metal form were analyzed. After KOBO extrusion, significant differences were observed in the microstructure and properties between the materials derived from cold-compacted powder, sintered powder, and reference cast magnesium. Due to the application of KOBO, apart from α-Mg grain refinement, the MgO derived from the initial powder’s surface was refined to fine regular particles surrounded by magnesium. Their bands curved in the perpendicular plane and were oriented with the extrusion direction of the formed network, which augmented some mechanical properties and changed the decohesion mechanism. The conducted experiments revealed that before extrusion by KOBO, the magnesium powder required sintering under pressure.

Orientation Dependence on Bending Deformation Behavior of Pure Zinc Single Crystals

Three-point bending tests were performed on pure zinc single crystals with different crystal orientations to investigate orientation dependence on bending deformation behavior. With basal planes parallel to the neutral planes, the specimens deformed due to basal slips and formed a gull shape after deformation. On the other hand, specimens whose neutral planes are perpendicular to the basal planes and neutral axes are perpendicular to [0001] deformed due to second order pyramidal 〈c + a〉 slips, {1012} twinning and basal slips within {1012} twins, displaying a V shape. The bending deformation behavior of pure zinc single crystals was found to show strong orientation dependence. Also, the bending deformation behavior of pure zinc single crystals was found to differ from that of pure magnesium single crystals when the neutral plane and neutral axis are respectively perpendicular to the basal planes and [0001].

Analysis of a Pure Magnesium Membrane Degradation Process and Its Functionality When Used in a Guided Bone Regeneration Model in Beagle Dogs.

For the surgical technique of guided bone regeneration (GBR), the choice of available barrier membranes has until recently not included an option that is mechanically strong, durable, synthetic and resorbable. The most commonly used resorbable membranes are made from collagen, which are restricted in their mechanical strength. The purpose of this study is to evaluate the degradation and regeneration potential of a magnesium membrane compared to a collagen membrane. In eighteen beagle dogs, experimental bone defects were filled with bovine xenograft and covered with either a magnesium membrane or collagen membrane. The health status of the animals was regularly monitored and recorded. Following sacrifice, the hemimandibles were prepared for micro-CT (μ-CT) analysis. Complications during healing were observed in both groups, but ultimately, the regenerative outcome was similar between groups. The μ-CT parameters showed comparable results in both groups in terms of new bone formation at all four time points. In addition, the μ-CT analysis showed that the greatest degradation of the magnesium membranes occurred between 1 and 8 weeks and continued until week 16. The proportion of new bone within the defect site was similar for both treatment groups, indicating the potential for the magnesium membrane to be used as a viable alternative to collagen membranes. Overall, the new magnesium membrane is a functional and safe membrane for the treatment of defects according to the principles of GBR.