Magnesium-based Alloys Research Articles

Wear behavior of different coated tools in MQL-assisted milling of magnesium-based rare-earth alloys

One of the most important and often employed indicators for describing machinability and machining quality is tool wear. While flank wear is commonly used to gauge the extent of a worn scar, tool wear is characterized more by its shape than its size. To quantify the wear shape, more specific data concerning the wear contour is required. With this aim, the present work addresses the fundamental wear mechanisms and failure modes of several coated tools used in the mechanical milling of rare-earth magnesium (Mg-RE) alloys. Uncoated, edge-strengthened, TiAlN-coated, and diamond-coated tools were tested under dry and minimal quantity lubrication (MQL) conditions. The cutting energy flow and consumption rules governing the tool wear processes were quantified using the exergy analysis theory. The results indicate that the cutting performances of tools and the surface quality are both enhanced by the MQL through reducing adhesion wear. For the unstrengthened tool, a tool wear reduction of 55% is achieved by the MQL. While for the TiAlN-coated tool, the tool wear can be furtherly suppressed by 49%.

Microstructure and Physical Properties of Nonmagnesium and Magnesium-Based High-Entropy Alloys: A Comparison Study

Abstract In this investigation, (Ti-Mo-Zr)60Co20Cr20, (Ti-Mo-Zr)60Al30Si10 (non-magnesium-based), and (Ti-Mo-Zr)60Cu10Mg30 (magnesium-based) high-entropy alloy (HEA) samples are prepared via mechanical milling and then by spark plasma sintering technique. The microstructure morphology is examined using x-ray diffraction and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The microstructure reveals that there would be a strong correlation between phase structure and sustainability for localized corrosion behavior. The lowest crystallite size of the magnesium-based HEA powder mixture suggests the highest corrosion resistance because of the solid-solution face-centered cubic and body-centered cubic phases for 20 h of milling. The correlation between the microstructural morphology and functional properties such as hardness, corrosion resistance, and potentiodynamic parameters are compared for both magnesium-based and non-magnesium-based HEAs and analyzed to elucidate their suitability for lightweight vehicle applications.

Conversion of CH4 and Hydrogen Storage via Reactions with MgH2-12Ni.

The main key to the future transition to a hydrogen economy society is the development of hydrogen production and storage methods. Hydrogen energy is the energy produced via the reaction of hydrogen with oxygen, producing only water as a by-product. Hydrogen energy is considered one of the potential substitutes to overcome the growing global energy demand and global warming. A new study on CH4 conversion into hydrogen and hydrogen storage was performed using a magnesium-based alloy. MgH2-12Ni (with the composition of 88 wt% MgH2 + 12 wt% Ni) was prepared in a planetary ball mill by milling in a hydrogen atmosphere (reaction-involved milling). X-ray diffraction (XRD) analysis was performed on samples after reaction-involved milling and after reactions with CH4. The variation of adsorbed or desorbed gas over time was measured using a Sieverts'-type high-pressure apparatus. The microstructure of the powders was observed using a scanning transmission microscope (STEM) with energy-dispersive X-ray spectroscopy (EDS). The synthesized samples were also characterized using Fourier transform infrared (FT-IR) spectroscopy. The XRD pattern of MgH2-12Ni after the reaction with CH4 (12 bar pressure) at 773 K and decomposition under 1.0 bar at 773 K exhibited MgH2 and Mg2NiH4 phases. This shows that CH4 conversion took place, the hydrogen produced after CH4 conversion was then adsorbed onto the particles, and hydrides were formed during cooling to room temperature. Ni and Mg2Ni formed during heating to 773 K are believed to cause catalytic effects in CH4 conversion. The remaining CH4 after conversion is pumped out at room temperature.

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.

Prospective evaluation of ultrasound features of magnesium-based bioabsorbable screw resorption in pediatric fractures.

Bioabsorbable magnesium-based alloy screws release gas upon resorption. The resulting findings in the adjacent soft tissues and joints may mimic infection. The aim of the study was to evaluate the ultrasound (US) findings in soft tissues and joints during screw resorption. Prospectively acquired US studies from pediatric patients treated with magnesium screws were evaluated for screw head visibility, posterior acoustic shadowing, twinkling artifact, foreign body granuloma, gas (soft tissue, intra-articular), alterations of the skin and subcutaneous fat, perifascial fluid, localized fluid collections, hypervascularization, and joint effusion. Sixty-six US studies of 28 pediatric patients (nfemale = 9, nmale = 19) were included. The mean age of the patients at the time of surgery was 10.84years; the mean time between surgery and ultrasound was 128.3days (range = 6-468days). The screw head and posterior acoustic shadowing were visible in 100% of the studies, twinkling artifact in 6.1%, foreign body granuloma in 92.4%, gas locules in soft tissue in 100% and intra-articular in 18.2%, hyperechogenicity of the subcutaneous fat in 90.9%, cobblestoning of the subcutaneous fat in 24.2%, loss of normal differentiation between the epidermis/dermis and the subcutaneous fat in 57.6%, localized fluid collection in 9.9%, perifascial fluid in 12.1%, hypervascularization in 27.3%, and joint effusion in 18.2%. US findings in pediatric patients treated with magnesium screws strongly resemble infection, but are normal findings in the setting of screw resorption. Bioabsorbable magnesium-based alloy screws release gas during resorption. The resulting US findings in the adjacent soft tissues and joints in pediatric patients may mimic infection, but are normal findings. • Bioabsorbable magnesium-based alloy screws release gas upon resorption. • The resulting ultrasound findings in children's soft tissues and joints closely resemble those of soft tissue infection or osteosynthesis-associated infection. • Be familiar with these ultrasound findings in order to avoid inadvertently misdiagnosing a soft tissue infection or osteosynthesis-associated infection.

Pitting corrosion behavior and corrosion protection performance of cold sprayed double layered noble barrier coating on magnesium-based alloy in chloride containing solutions

Nitrogen processed, cold sprayed commercially pure (CP)-Al coatings on Mg-based alloys mostly lack acceptable hardness, wear resistance and most importantly are highly susceptible to localized corrosion in chloride containing solutions. In this research, commercially pure α-Ti top coating having good pitting potential (∼ 1293 mVSCE), high microhardness (HV0.025: 263.03) and low wear rate was applied on a CP-Al coated Mg-based alloy using high pressure cold spray technology. Potentiodynamic polarization (PDP) curves indicated that the probability of transition from metastable pits to the stable pits for cold spayed (CS) Al coating is considerably higher compared to that with the CS Ti top coating (for Ti/Al/Mg system). In addition, CS Ti top coating was in the passivation region in most pH ranges even after 48 h immersion in 3.5 wt% NaCl solution. The stored energy in the CS Ti top coating (as a passive metal) was presumed to be responsible for the easy passivation. Immersion tests indicated no obvious pits formation on the intact CS Ti top coating surface and revealed effective corrosion protection performance of the CS double layered noble barrier coatings on Mg alloys in 3.5 wt% NaCl solution even after 264 h.

Phase evolution, hydrogen storage thermodynamics, and kinetics of ternary Mg98Ho1.5Fe0.5 alloy

Rare earth elements and transition metals have been found to improve the hydrogen storage characteristics of magnesium-based alloys. This study investigated the Mg-Ho-Fe (MHF) ternary alloy prepared using the vacuum induction melting technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), pressure-composition-temperature (PCT), and differential scanning calorimetry (DSC) were used to analyze the alloy's phase transitions, microstructure, thermodynamics, and kinetic properties. The results reveal that the Mg98Ho1.5Fe0.5 alloy forms a solid solution with Ho and Fe in the magnesium matrix. Upon hydrogen absorption, the activated alloy transforms into a mixture of Mg/MgH2 phases and nanoscale HoH2 phases. Notably, only the MgH2 phase decomposes during hydrogen desorption, while the HoH2 phase remains unchanged, exhibiting a positive catalytic effect. The alloy demonstrates excellent hydrogen absorption kinetics, achieving a capacity of 5.56 wt% H2 within 10 min at 360 °C, owing to the combined catalytic effects of Ho and Fe. The activation energy for hydrogen desorption is found to be 135.87 kJ/mol, which is lower than that of the activation energies of pure MgH2 and MgFe alloys, indicating an enhancement in desorption kinetics. Moreover, the enthalpy and entropy changes for hydrogen absorption and desorption are determined to be –70.51 kJ/mol H2, –125.62 J/(K·mol) H2, 72.83 kJ/mol H2, and 128.95 J/(K·mol) H2, respectively. Furthermore, it is worth noting that the thermodynamic properties of the alloy are improved due to the catalytic effect of Ho and Fe.

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.

Modelling and Simulation of Composition and Mechanical Properties of High Entropy Magnesium-Based Multi Component Alloy

Magnesium alloys are high potential materials for application in the aerospace and automotive industries due to their lightweight properties. They can help to lower dead weight and fuel consumption to contribute to sustainability and efficiency. It is possible to achieve high specific strength and high stiffness of the alloys by varying compositions of alloying elements. Applications of magnesium are limited due to its low strength and relatively low stiffness. This research focuses on a recipe of multi component alloys of magnesium with varied percentages of Mg, Al, Cu, Mn and Zn obtained from literature and optimizes the percentage compositions to obtain for high specific strength and specific stiffness. Relationships among percentage constituents of the alloy components are examined in Matlab R2022b using multiple linear regression. Optimization is achieved using genetic algorithm to determine the specific strengths and stiffness. The resulting optimal alloy component percentages by weight are used for microstructure simulation of thermodynamic properties, diffusion and phase transformations of proposed alloy is done in MatCalc software version 6.04. Results show potential for improved mechanical properties resulting from disordered structure in the high entropy magnesium alloy. Future research should focus on production and characterization of the proposed alloy.

Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy

Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications.

Microstructure and Corrosion Behaviour of Mg-Ca and Mg-Zn-Ag Alloys for Biodegradable Hard Tissue Implants

Trauma orthopaedic surgery was the first domain to use degradable metallic implants made of magnesium alloys since the early 20th century. Unfortunately, the major limitation that consists of rapid degradation and subsequent implant failure, which occur in physiological environments with a pH between 7.4 and 7.6, prevents its widespread application. The biggest challenge in corrosion assay is the choice of the testing medium in order to reproduce more closely in vivo conditions. The current study was focused on two Mg-Zn-Ag alloys (Mg7Zn1Ag and Mg6Zn3Ag) and the Mg1Ca alloy. Dulbecco’s Modified Eagle Medium (DMEM) and Kokubo’s simulated body fluid solution (SBF) were selected as testing mediums and we follow the corrosion evaluation by the corrosion rate and mass loss. Also, the corrosion behaviour was interpreted in correlation with the microstructural features and alloying elements of the experimental magnesium-based alloys revealed by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDX). The experimental results highlight the more corrosive nature of the SBF environment and that a higher percentage of silver (2.5 wt.%) exhibited a better corrosion resistance. We consider that the magnesium alloy Mg6Zn3Ag showed valuable biodegradation characteristics to be considered as raw materials for manufacturing small trauma implants.

Facile bioactive transformation of magnesium alloy surfaces for surgical implant applications.

The market for orthopedic implant alloys has seen significant growth in recent years, and efforts to reduce the carbon footprint of medical treatment (i.e., green medicine) have prompted extensive research on biodegradable magnesium-based alloys. Magnesium alloys provide the mechanical strength and biocompatibility required of medical implants; however, they are highly prone to corrosion. In this study, Mg-9Li alloy was immersed in cell culture medium to simulate degradation in the human body, while monitoring the corresponding effects of the reaction products on cells. Variations in pH revealed the generation of hydroxyl groups, which led to cell death. At day-5 of the reaction, a coating of MgCO3 (H2O)3, HA, and α -TCP appeared on sample surfaces. The coating presented three-dimensional surface structures (at nanometer to submicron scales), anti-corrosion effects, and an altered surface micro-environment conducive to the adhesion of osteoblasts. This analysis based on bio-simulation immersion has important implications for the clinical use of Mg alloys to secure regenerated periodontal tissue.

In Vivo Assessment of High-Strength and Corrosion-Controlled Magnesium-Based Bone Implants.

The biodegradable nature of magnesium in aqueous mediums makes it an attractive material for various biomedical applications when it is not recommended that the material stay permanently in the body. Some of the main challenges that hinder the use of magnesium for bone fracture repair are its limited mechanical strength and fast corrosion rates. To this end, we developed a novel Mg-Zn-Ca-Mn-based alloy and post-fabrication methods that can deliver high-strength and corrosion-controlled implant materials to address these challenges. This study is focused on assessing the in vitro corrosion and in vivo biocompatibility of the developed magnesium-based alloy and post-fabrication processes. The developed heat treatment process resulted in an increase in the microhardness from 71.9 ± 5.4 HV for the as-cast Mg alloy to as high as 98.1 ± 6.5 HV for the heat-treated Mg alloy, and the ceramic coating resulted in a significant reduction in the corrosion rate from 10.37 mm/yr for the uncoated alloy to 0.03 mm/yr after coating. The in vivo assessments showed positive levels of biocompatibility in terms of degradation rates and integration of the implants in a rabbit model. In the rabbit studies, the implants became integrated into the bone defect and showed minimal evidence of an immune response. The results of this study show that it is possible to produce biocompatible Mg-based implants with stronger and more corrosion-controlled properties based on the developed Mg-Zn-Ca-Mn-based alloy and post-fabrication methods.

Effect of sintering temperature on crystal structure and physical properties of the Mg0,92Zn0,05C0,03 Alloy

The effect of sintering temperature on the crystal structure and physical properties of the Mg0,92Zn0,05C0,03 alloy has been studied. Magnesium-based alloys are one of the alloys that have been used in industry, the health sector, and as biodegradable materials and biomaterials. The aim of this study was to determine the effect of temperature and sintering holding time on crystal size, dislocation density, microlattice strain, and yield strength, porosity and density of Mg0,92Zn0,05C0,03 alloy. The results of testing the crystal structure of the alloy Mg0,92Zn0,05C0,03 with an X-ray diffractometer showed several diffraction peaks consisting of the main phase α–Mg and a small part of the MgZn phase. Testing of Mg0,92Zn0,05C0,03 alloy after sintering with variations in temperature and 90 minutes holding time for crystal size showed that the higher the sintering temperature (425 0C to 575 0C) the crystal size value decreased significantly from 82.36 nm to 18.75 nm, and the dislocation density increased from 0.113 to 0.868 lines/mm2. For micro strain decreased from 0.015 to 0.0087. However, in the very small porosity test, the increase was from 29.8% to 31.9%. As well as for density (1.8 gr/cm3) and yield strength (274 MPa) there was no significant decrease of around 1.4%, but the synthesized Mg0,92Zn0,05C0,03 alloy fulfilled as a bone implant bio material.hhThe effect of sintering temperature on the crystal structure and physical properties of the Mg0,92Zn0,05C0,03 alloy has been studied. Magnesium-based alloys are one of the alloys that have been used in industry, the health sector, and as biodegradable materials and biomaterials. The aim of this study was to determine the effect of temperature and sintering holding time on crystal size, dislocation density, microlattice strain, and yield strength, porosity and density of Mg0,92Zn0,05C0,03 alloy. The results of testing the crystal structure of the alloy Mg0,92Zn0,05C0,03 with an X-ray diffractometer showed several diffraction peaks consisting of the main phase α–Mg and a small part of the MgZn phase. Testing of Mg0,92Zn0,05C0,03 alloy after sintering with variations in temperature and 90 minutes holding time for crystal size showed that the higher the sintering temperature (425 0C to 575 0C) the crystal size value decreased significantly from 82.36 nm to 18.75 nm, and the dislocation density increased from 0.113 to 0.868 lines/mm2. For micro strain decreased from 0.015 to 0.0087. However, in the very small porosity test, the increase was from 29.8% to 31.9%. As well as for density (1.8 gr/cm3) and yield strength (274 MPa) there was no significant decrease of around 1.4%, but the synthesized Mg0,92Zn0,05C0,03 alloy fulfilled as a bone implant bio material.

Surface Modification on Magnesium Alloys’ Hardness and Microstructure Using Friction Stir Processing – A Review

Low density of magnesium-based alloy is one potential as the lightest structural material for light weight-high strength applications for automotive and aerospace. Severe plastic deformation (SPD) together with thermomechanical processing are proved to be a successful method for attaining desired microstructural modifications through achieving fine and highly misoriented microstructures and creating various structures to the bulk properties of magnesium alloy. The material's deformation can result in an altered microstructure that is gainful to the material's requirements. However, the poor deformability of magnesium and its alloys limits the application of the thermomechanical approach. Controlling over temperature and deformation rate is hard to achieve. Among the thermomechanical processes, friction stir processing (FSP) offers an easy way to achieve process stability and mechanical properties enhancement by heat treatment which results in the closure of porosity and refined grain size. During this process, heat is generated by the rotation of the FSP processing tool. Few process parameters such as rotational and traverse speeds should be controlled to make FSP stay within the defined processing condition. It is critical to set the right tool rotational speed as well as traverse speed to ensure adequate heat generation. As there are no established standards for operating the FSP, the only solution is to experiment with different settings to find the best parameter which will produce better quality on processed magnesium alloy workpiece. This paper explores earlier studies on surface modification via FSP technique to improve the mechanical properties strengthening of magnesium alloy mainly on grain size and hardness. The surface modification was done mostly on popular series of magnesium alloy (AZ series) using different tool material, tool geometry and different parameters combination. A comprehensive view of surface modification on magnesium alloys which includes the FSP tool and workpiece material used, variations of FSP parameters settings as well as the effect on hardness and microstructure analysis will be discussed.

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.

Relationships between Processing and Properties of Magnesium-Based Alloys

Magnesium alloys can be used in a wide range of applications, from lightweight structural and transport applications to biomaterials [...]

Enhancing the Mechanical Properties of AZ31D Alloy by Reinforcing Nanosilicon Carbide/Graphite

Magnesium-based alloys were more prevalent in automobile applications owing to their mechanical properties, low mass, and density. However, its poor mechanical properties are restricting its applications. Therefore, the present study focuses on improving the mechanical properties of AZ31D alloy by reinforcing silicon carbide (SiC) and graphite (Gr) nanoparticles with weight fractions of 2%, 4%, and 6% using stir-casting technique. The microstructure analysis was performed using a scanning electron microscope. The elemental analysis was confirmed using energy-dispersive spectroscopy, and X-ray diffraction was used to study various phases in the nanocomposites. Further, the mechanical properties, such as microhardness, ultimate tensile strength, yield strength, and compression strength of the nanocomposites, were significantly improved by 53%, 59%, 62%, and 82%, respectively, as compared with base alloy.

Research Progress on Microstructure Evolution and Strengthening-Toughening Mechanism of Mg Alloys by Extrusion.

Magnesium and magnesium-based alloys are widely used in the transportation, aerospace and military industries because they are lightweight, have good specific strength, a high specific damping capacity, excellent electromagnetic shielding properties and controllable degradation. However, traditional as-cast magnesium alloys have many defects. Their mechanical and corrosion properties cause difficulties in meeting application requirements. Therefore, extrusion processes are often used to eliminate the structural defects of magnesium alloys, and to improve strength and toughness synergy as well as corrosion resistance. This paper comprehensively summarizes the characteristics of extrusion processes, elaborates on the evolution law of microstructure, discusses DRX nucleation, texture weakening and abnormal texture behavior, discusses the influence of extrusion parameters on alloy properties, and systematically analyzes the properties of extruded magnesium alloys. The strengthening mechanism is comprehensively summarized, the non-basal plane slip, texture weakening and randomization laws are comprehensively summarized, and the future research direction of high-performance extruded magnesium alloys is prospected.

Microstructure and mechanical properties of magnesium alloy reinforced with TiB2 and B4C processed through friction stir processing

Due to its light weight, particulate magnesium metal matrix composites have become a popular choice for industrial applications in the fabrication of vehicles. There were a few practical challenges with creating magnesium-based alloy composites, such as flammability and significant shrinkage. Despite the real time fabrication limitations, researchers are being attracted in magnesium metal matrix composites that are reinforced with particulate reinforcements due their high strength to weight ratio. Friction Stir Processing is one of the most widely used processes used to produce Magnesium metal matrix composites. Because of low process temperature, it is mostly impervious to chemical reactions that are caused during conventional manufacturing processes. The present research work emphasis on the development of AZ31alloy composite by friction stir processing reinforced with TiB2 and B4C particulate reinforcements. The effect of added reinforcement in mechanical properties like tensile strength, hardness, and wear performance were observed. The addition of TiB2 helps in improving the ultimate tensile strength of the magnesium MMC. SEM observations have shown that the number of passes increased it refined the grain size. Particle sizes were also seen to be reduced in size as the increment in passes. The variation in the tensile strength was not impressive; on the other hand, the hardness of FSPed samples has increased in comparison to the base material. Samples have shown improvement in resistance to the wear rate as an increase in traverse speed and it was seen to increase that resistance to wear was increased as the passes were incremented.