The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investig...The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investigated.For this purpose,the Mg-0.6Si,Mg-1.34Si,and Mg-3Si(wt%)alloys were considered as hypoeutectic,eutectic,and hypereutectic alloys,respectively.By decreasing the geometrical modulus of the solidifying section(increasing cooling rate),remarkable grain refinement,refining the dendrite arm spacing(DAS),and modification of Mg_(2)Si particles were achieved.Moreover,the grain size was refined via Si addition in the hypoeutectic range,while coarsening of grain size at high Si concentrations was observed.The results of shear punch testing and hardness measurements demonstrated that the ultimate shear strength(USS)and hardness increased by increasing the cooling rate during solidification.Moreover,Si addition generally improved hardness,while the highest USS level was achieved for the eutectic alloy due to the fine grain size and strengthening effect of the eutectic constituent.However,regarding the hypereutectic Mg-3Si alloy that exhibited high hardness,the shear properties were inferior due to the detrimental effect of the primary Mg_(2)Si particles.Finally,the results were discussed with consideration of the relationship between strength and hardness,for which the critical effect of Si was clarified.展开更多
A CaCO_(3)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 o...A CaCO_(3)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 CaCO_(3)layer and an inner(Ca,Mg)CO_(3)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 CaCO_(3)coating on AZ41 Mg alloy,which is mainly benefit from the assistance of the ultrasound.Ultrasound accelerates the nucleation of CaCO_(3)crystals and assists the removal of hydrogen bubbles.Additionally,corrosion mechanism was suggested and discussed for the CaCO_(3)coating.展开更多
Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated ...Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.展开更多
Rechargeable magnesium batteries(RMBs)have attracted much attention due to the high theoretical capacity(3833 mAh cm−3)of magnesium metal negative electrode and abundant resources.However,the preparation of ultra-thin...Rechargeable magnesium batteries(RMBs)have attracted much attention due to the high theoretical capacity(3833 mAh cm−3)of magnesium metal negative electrode and abundant resources.However,the preparation of ultra-thin magnesium foils faces the problems of rolling difficulty and high processing cost,while the use of thick magnesium foils leads to low utilization of magnesium and reduces the energy density.To tackle the above problems,we successfully prepared ultra-thin magnesium foils based on electrolytic process and investigated the effect of different substrates.The magnesium foils prepared using Mo substrate have more uniform surface morphology and lower surface roughness,which is attributed to the lower magnesium nucleation overpotential of Mo substrate.Meanwhile,density functional theory calculations show that the adsorption energy of Mo on Mg is more negative,which is conducive to achieving uniform nucleation and deposition of Mg.The Mg deposition on Mo substrate undergoes the characteristic stages of transient nucleation,nucleus accretion,multidirectional heterotopic growth,and columnar crystal stacking,and ultimately the formation of a dense deposited layer.In addition,the prepared ultra-thin Mg foil with Mo substrate can stably cycle for 1000 h at 3 mA cm^(-2) with high utilization of 50% in the symmetric cell.This study develops a facile method for the preparation of ultra-thin Mg foils,which opens up a new path for developing high-performance ultra-thin negative electrodes for RMBs.展开更多
Magnesium(Mg)alloys are promising candidates for biodegradable implants and medical devices due to their biocompatibility,mechanical properties,and ability to degrade in vivo,thereby eliminating the need for secondary...Magnesium(Mg)alloys are promising candidates for biodegradable implants and medical devices due to their biocompatibility,mechanical properties,and ability to degrade in vivo,thereby eliminating the need for secondary removal surgeries[1,2].However,their clinical adoption is hindered by rapid corrosion in physiological environments[3–5].Due to the high chemical reactivity of magnesium substrates and the inability of primary corrosion degradation products to form ideal protective layers,no effective scientific guidance has yet been identified from fundamental material science to address the rapid degradation of bare Mg[6–8].Surface modification strategies equivalently create new materials wrapped in a matrix,which can thus be extensively explored to enhance the corrosion resistance of Mg alloys while endowing them with tailored biological functionalities[9,10].展开更多
With the rapid development of Mg alloys,deeper understanding to the thermodynamic and diffusional kinetic behavior of intermetallic compounds(IMCs)is important for studying the effect of alloying elements to the micro...With the rapid development of Mg alloys,deeper understanding to the thermodynamic and diffusional kinetic behavior of intermetallic compounds(IMCs)is important for studying the effect of alloying elements to the microstructure evolution.Specially,a systematic quantitative investigation on the diffusional growth of IMCs is of great necessity.However,the works studying the elemental diffusion behaviors of multiple-element IMCs are rare in magnesium alloy systems.The current work takes the ternary Mg-Al-Zn system as research target,and combines the diffusion couple technique,phase stability diagrams,in-situ observation technique and numerical inverse method to investigate the temperature-dependent kinetic coefficients.The parabolic growth constant(PGC)and interdiffusion coefficients for Mg solid-solution phase andγ-Mg_(17)Al_(12),β-Mg_(2)Al_(3),ε-Mg_(23)Al_(30),MgZn_(2),Mg_(2)Zn_(3),τ-Mg_(32)(Zn,Al)49 andφ-Mg_(5)Zn_(2)Al_(2) IMCs in the Mg-Al-Zn alloy system are determined.By comparing the current experimental with calculation results,the rate-controlling factor of the temperature-dependent diffusion growth ofφ,τandεternary IMCs in the Mg-Al-Zn system is further discussed in detail.展开更多
A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainab...A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid(ILs)during the LePEO process for LA91 magnesium-lithium(Mg-Li)alloy.Results show that the ionic liquid BmimBF_(4)participates in the LePEO coating formation process,causing an increment in coating thickness and surface roughness.The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process(LePEO-IL).After adding BmimBF_(4),corrosion current density decreases from 1.159×10^(−4)A·cm^(−2)to 8.143×10^(−6)A·cm^(−2).The impedance modulus increases to 1.048×10^(4)Ω·cm^(−2)and neutral salt spray remains intact for 24 h.The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid.The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.展开更多
Biodegradable magnesium-matrix composites(BMMCs)added with bone-like compounds such as hydroxyapatite(HA)have promising orthopedic application potential,but the in vivo results of BMMCs are insufficient,and the differ...Biodegradable magnesium-matrix composites(BMMCs)added with bone-like compounds such as hydroxyapatite(HA)have promising orthopedic application potential,but the in vivo results of BMMCs are insufficient,and the difference between in vitro and in vivo are not clarified.In this work,Mg-Zn-Nd-Zr/(10/15/20wt%)HA(Ca_(10)(PO_(4))_(6)OH_(2))composites were prepared through friction stirring processing(FSP).It was found that corrosion rate of the composites increased with increase of the HA content,where the corrosion rate from hydrogen evolution of the Mg/10wt%HA was about 0.107 mm/y,showing better corrosion resistance compared with other BMMCs,and the agglomeration of HA powders significantly aggravated the localized corrosion.The ALP specific activity of the MC3T3-E1 cells cultured for14 days with Mg/10wt%HA(2.12 IU/mg)was higher than that of the matrix(1.85 IU/mg),but there was no difference with the FSP group(2.13 IU/mg).In the early implantation of the rabbit femur,bone volume fraction(BV/TV)of Mg/10wt%HA was 10.69,which was higher than that of the FSP group(6.35).The histological staining showed that the Mg/10wt%HA implant was surrounded by more trabecular bone tissue,exhibiting better osteoinductive regeneration.The Mg-Zn-Nd-Zr/HA composites exhibit higher osteogenic activity in vivo differently from in vitro osteogenic expression.展开更多
The degradation behavior of biodegradable Mg alloys has become a research hotspot in the fields about biodegradable metallic materials.While the most of the related publications mainly focused on the degradation rate ...The degradation behavior of biodegradable Mg alloys has become a research hotspot in the fields about biodegradable metallic materials.While the most of the related publications mainly focused on the degradation rate of Mg-based materials,but rare to care about the changes of their mechanical properties during the immersion period,which can significantly affect their service performance.The link between residual strength and Mg degradation is not appreciated enough.In this work,a series media were constructed based on Hanks’solution,the effects of inorganic ions on the degradation rate and mechanical integrity of Mg-Zn-Y-Nd alloy were investigated.The results indicated that the degradation behavior of Mg alloy was mainly controlled by degradation products and there is no direct correspondence between the degradation rate change and mechanical integrity of Mg alloy.The relevant findings are beneficial for selecting the monitoring index in Mg corrosion tests and evaluating the service reliability of Mg alloys for biomedical applications.展开更多
Magnesium-based biomaterials(MBMs)are one of the most promising materials for tissue engineering due to their unique mechanical properties and excellent functional properties.This review describes the development,adva...Magnesium-based biomaterials(MBMs)are one of the most promising materials for tissue engineering due to their unique mechanical properties and excellent functional properties.This review describes the development,advantages,and challenges of MBMs for biomedical applications,especially for tissue repair and regeneration.The history of the use of MBMs from the beginning of the 20th century is traced,and the transformative advances in contemporary applications of MBMs in areas such as orthopedics and cardiovascular surgery are emphasized.The review also provides insight into the signaling pathways affected by MBMs,such as the PI3K/Akt and RANKL/RANK/OPG pathways,which are critical for osteogenesis and angiogenesis.The review advocates that future research should focus on optimizing alloy compositions,surface modification and exploring innovative technologies such as 3D printing to improve the efficacy of MBMs in complex tissue repair.The potential of MBMs to tissue engineering and regenerative medicine is significant,urging further exploration and interdisciplinary collaboration to maximize their therapeutic effects.展开更多
The creep properties, microstructural characteristics and creep mechanisms of as-cast Mg-5Bi-5Sn(BT55) alloy without and with Mn(BTM550) addition were investigated via creep at 423, 448, and 473 K as well as stresses ...The creep properties, microstructural characteristics and creep mechanisms of as-cast Mg-5Bi-5Sn(BT55) alloy without and with Mn(BTM550) addition were investigated via creep at 423, 448, and 473 K as well as stresses of 30, 50 and 75 MPa. The results indicate that adding Mn can result in the formation of primary and the dynamic precipitated α-Mn phases. In addition, the morphology of the precipitated Mg_(3)Bi_(2) phase and the orientation relationship between Mg_(2)Sn precipitates and α-Mg can be effectively modified. Tailoring the microstructural characteristics is responsible for the improved creep performance of BTM550 alloy. The dominant creep mechanisms in BT55 and BTM550 alloys are dislocation cross-slip and climb, respectively. Furthermore, twinning and pyramidal slip play an assisting part in both alloys during creep process.展开更多
The tensile tests of the extruded ZK60 Mg containing a longitudinal weld seam were carried out at room and elevated temperatures, and the effects of induced microstructure inhomogeneity on tensile deformation behavior...The tensile tests of the extruded ZK60 Mg containing a longitudinal weld seam were carried out at room and elevated temperatures, and the effects of induced microstructure inhomogeneity on tensile deformation behavior was clarified. The results show that the deformation mode, dynamic recrystallization(DRX), texture evolution and mechanical properties are strongly affected by the longitudinal weld seam,temperature, and loading direction. The room temperature(RT) deformation of welding zone is controlled by the dislocation slips with the association of some twins, while twinning plays significant roles in the accommodation of c-axis strain of the coarse grains on matrix zone.The deformation at RT stretched along extrusion direction(ED) and transverse direction(TD) are controlled by basal slip/twinning and basal slip/prismatic slip/twinning, respectively. During high temperature tension, the dislocation cross slip of pyramidal slip is activated, and grain boundary sliding occurred in welding zone, leading to the superplastic behavior. With the increase of tensile temperature, the predominant DRX mode is transformed from continuous DRX to discontinuous DRX. Moreover, the basal poles of the grains spread from TD towards ED with the decrease of maximum pole intensity when stretched along ED, while non-basal textures are transformed to (10-10) fiber texture when stretched along TD. The slip-dominated flow is seen during RT tension along ED, while twinning becomes predominant during RT tension along TD. The fine grain structure causes the superior RT tensile properties along ED of welding zone with ultimate tensile strength of 315 MPa and elongation to failure of 13.8%. With the increase of tensile temperature, the slipping-dominated deformation is transformed into twinning-dominated, causing the decrease of strength and increase of elongation.展开更多
Converting CO_(2)to valuable materials is attractive in environmental protection and resource utilization.In this study,a vapor-liquid interface reaction system for mass production of high-quality graphene is reported...Converting CO_(2)to valuable materials is attractive in environmental protection and resource utilization.In this study,a vapor-liquid interface reaction system for mass production of high-quality graphene is reported.The graphene obtained has high crystallinity and few defects during the reaction of CO_(2)and Mg melt.The growth mechanism of graphene is demonstrated in vapor-liquid interface area by combining the CO_(2)bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles.The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness.Additionally,the V-L reaction method ingeniously solves the dispersion of graphene in metal,providing a preparation strategy of Mg matrix composites with structure and function integration.展开更多
Grain boundaries play a significant role in the deformation of polycrystals.Their response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjo...Grain boundaries play a significant role in the deformation of polycrystals.Their response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjoining crystallites by changing their structure and geometry.The current study thus investigates the deformation behaviour of Mg bicrystals with 90°<1120>symmetric tilt boundary strained in plane-strain compression up to different final strains.Due to the initial soft orientation of the two crystals,activation of basal slip in each crystal gave rise to lattice rotation around the transverse direction towards the compression direction of the channel-die.Hundreds of single EBSD maps with a small step size were obtained from the GB region and stitched together to produce large panoramic maps of a macroscopic scale.Although very time-consuming,this technique has proven useful in clarifying the origin of the non-uniform deformation zones in the vicinity of the grain boundary and explains the mechanisms,by which the grain boundary was able to cope with the imposed strain before fracture.Interestingly,several variants of extension twins were observed as an additional deformation mechanism despite having negative Schmid factors.Systematic investigation of their resulting combined shear components with respect to the sample coordinate system revealed an alignment along the longitudinal direction of the channel-die,therefore justifying their nucleation.展开更多
A novel Mg-Al LDH film was in-situ prepared hydrothermally in an alkaline aqueous solution on an Al-alloyed AZ31 substrate.The structural,chemical and functional characteristics of the film were explored by means of s...A novel Mg-Al LDH film was in-situ prepared hydrothermally in an alkaline aqueous solution on an Al-alloyed AZ31 substrate.The structural,chemical and functional characteristics of the film were explored by means of scanning electron microscope(SEM),X-ray diffraction(XRD),energy dispersive spectrometer(EDS),polarization curve,AC impedance and salt immersion tests,respectively.The anti-corrosion results indicated that the Mg-Al LDH film on the Al-alloyed AZ31 surface could effectively protect the AZ31 from corrosion attack even after 90 days of immersion in 3.5 wt.%NaCl solution.The protection performance is surprisingly better than most of the reported coatings on Mg alloys.More interestingly,when the Mg-Al LDH film was scratched,the exposed Al-alloyed surface might gradually release metal ions and re-generate dense LDH nano-sheets in the corrosive environment to inhibit the further corrosion there,exhibiting a self-repairing behavior.The combination of the benign long-term protection and desirable self-repairing performance in this new process of surface-alloying and LDH-formation may significantly extend the practical application of magnesium alloys.展开更多
Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time(IDT) in the wire and arc ...Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time(IDT) in the wire and arc additive manufacturing(WAAM) process of Mg alloy.The thermal couples were used to monitor the thermal history during the WAAM process. Additionally, the effect of different IDTs on the microstructure characteristics and resultant mechanical properties of WAAM-processed Mg alloy thin-wall were investigated. The results showed that the stable temperature of the thin-wall component could reach 290 ℃ at IDT=0s, indicating that the thermal accumulation effect was remarkable. Consequently, unimodal coarse grains with an average size of 39.6 μm were generated, and the resultant room-temperature tensile property was poor. With the IDT extended to 60s, the thermal input and thermal dissipation reached a balance, and the stable temperature was only 170 ℃, closing to the initial temperature of the substrate. A refined grain structure with bimodal size distribution was obtained. The remelting zone had fine grains with the size of 15.2 μm, while the arc zone owned coarse grains with the size of 24.5 μm.The alternatively distributed coarse and fine grains lead to the elimination of strength-ductility trade-off. The ultimate tensile strength and elongation of the samples at IDT=60s are increased by 20.6 and 75.0% of those samples at IDT=0s, respectively. The findings will facilitate the development of additive manufacturing processes for advanced Mg alloys.展开更多
A new method of the formation of composite coatings with the function of active corrosion protection of magnesium alloys was developed using the plasma electrolytic oxidation(PEO) method. Susceptibility of PEO-layers ...A new method of the formation of composite coatings with the function of active corrosion protection of magnesium alloys was developed using the plasma electrolytic oxidation(PEO) method. Susceptibility of PEO-layers to pitting formation was evaluated using localized electrochemical methods(SVET/SIET). The morphological features and electrochemical properties of composite coatings were studied using SEM/EDX, XRD, micro-Raman spectroscopy and EIS/PDP measurements, respectively. The effect of surface layers impregnation with corrosion inhibitor on their protective properties in a corrosive environment was established. Additional protection was achieved using controllable coating pore sealing with polymer. It was found that the polymer treatment of the PEO-layer does not reduce the inhibitor’s efficiency. The formed protective composite inhibitor-and-polymer-containing layers decrease the corrosion current density of a magnesium alloy in a 3 wt.% Na Cl solution to three orders of magnitude. This predetermines the prospect of new smart coatings formation that significantly expand the field of application of electrochemically active materials. The mechanism of smart composite coating corrosion degradation was established. The antibacterial activity of the inhibitor-containing coatings against S. aureus methicillin-resistant strain was proved using the in vitro model. These protective layers are promising for reducing the incidence of implant-associated infections.展开更多
Grain growth directly influences the plasticity and strength of Mg alloys.As the grain size decreases from the microscale to the nanoscale,the plasticity of Mg alloys continually increases,whereas the strength first i...Grain growth directly influences the plasticity and strength of Mg alloys.As the grain size decreases from the microscale to the nanoscale,the plasticity of Mg alloys continually increases,whereas the strength first increases and later decreases.These trends are observed because the plastic deformation mechanism changes from dislocation–twinning dominance to grain boundary dominance.In this study,the factors influencing grain growth,such as the temperature of plastic deformation/annealing,second-phase particles and solute atoms,are examined to aid effective control of the grain size.Additionally,the mechanisms of grain growth,typically induced by strain and thermal activation,are clarified.Strain-induced grain boundary migration is attributable to the difference in the strain energy stored in adjacent grains with high-density dislocations.Heat-induced grain boundary migration is driven by the difference in the energy of the grain boundary/subgrain boundary and boundary curvature.Abnormal grain growth can be induced by anisotropy of the strain energy,anisotropy of the grain boundary mobility,depinning of the second phase and high misorientation gradient.展开更多
The effect of laser surface melting on the corrosion resistance of AZ31 Mg alloy in 0.1 M NaCl solution was investigated using different laser processing conditions(energy densities of 14 and 17 J cm^(-2)).Laser treat...The effect of laser surface melting on the corrosion resistance of AZ31 Mg alloy in 0.1 M NaCl solution was investigated using different laser processing conditions(energy densities of 14 and 17 J cm^(-2)).Laser treatment induced rough surfaces primarily composed of oxidized species of Mg.XPS analysis revealed that the surface concentration of Al increased significantly as a consequence of LSM.Electrochemical impedance spectroscopy showed that the laser treatment remarkably increased the polarization resistance of the AZ31 Mg alloy and induced a passive-like region of about 100 mV,as determined by potentiodynamic polarization.Analysis of the results obtained provide solid evidence that within the immersion times used in this study,LSM treatment increased the corrosion resistance of AZ31 Mg alloy under open circuit conditions and anodic polarization.展开更多
文摘The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investigated.For this purpose,the Mg-0.6Si,Mg-1.34Si,and Mg-3Si(wt%)alloys were considered as hypoeutectic,eutectic,and hypereutectic alloys,respectively.By decreasing the geometrical modulus of the solidifying section(increasing cooling rate),remarkable grain refinement,refining the dendrite arm spacing(DAS),and modification of Mg_(2)Si particles were achieved.Moreover,the grain size was refined via Si addition in the hypoeutectic range,while coarsening of grain size at high Si concentrations was observed.The results of shear punch testing and hardness measurements demonstrated that the ultimate shear strength(USS)and hardness increased by increasing the cooling rate during solidification.Moreover,Si addition generally improved hardness,while the highest USS level was achieved for the eutectic alloy due to the fine grain size and strengthening effect of the eutectic constituent.However,regarding the hypereutectic Mg-3Si alloy that exhibited high hardness,the shear properties were inferior due to the detrimental effect of the primary Mg_(2)Si particles.Finally,the results were discussed with consideration of the relationship between strength and hardness,for which the critical effect of Si was clarified.
基金the National Key Research and Development Program of China(Grant No.2021YFB3701100)the Natural Science Foundation Commission of China(Grant Nos.U20A20234and 51874062)+1 种基金Chongqing Foundation and Advanced Research Project(Grant No.cstc2019jcyj-zdxmX 0010)the Science and Technology Major Project of Shanxi Province(Grant No.20191102008)。
文摘A CaCO_(3)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 CaCO_(3)layer and an inner(Ca,Mg)CO_(3)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 CaCO_(3)coating on AZ41 Mg alloy,which is mainly benefit from the assistance of the ultrasound.Ultrasound accelerates the nucleation of CaCO_(3)crystals and assists the removal of hydrogen bubbles.Additionally,corrosion mechanism was suggested and discussed for the CaCO_(3)coating.
基金support from the National Natural Science Foundation of China(grant numbers 52275385 and U2167216).
文摘Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.
基金supported by the National Natural Science Foundation of China(No.U2037601)the National Key Research and Development Program(No.2023YFB3809500)the Chongqing Technology Innovation and Application Development Project(No.CSTB2022TIAD-KPX0028).
文摘Rechargeable magnesium batteries(RMBs)have attracted much attention due to the high theoretical capacity(3833 mAh cm−3)of magnesium metal negative electrode and abundant resources.However,the preparation of ultra-thin magnesium foils faces the problems of rolling difficulty and high processing cost,while the use of thick magnesium foils leads to low utilization of magnesium and reduces the energy density.To tackle the above problems,we successfully prepared ultra-thin magnesium foils based on electrolytic process and investigated the effect of different substrates.The magnesium foils prepared using Mo substrate have more uniform surface morphology and lower surface roughness,which is attributed to the lower magnesium nucleation overpotential of Mo substrate.Meanwhile,density functional theory calculations show that the adsorption energy of Mo on Mg is more negative,which is conducive to achieving uniform nucleation and deposition of Mg.The Mg deposition on Mo substrate undergoes the characteristic stages of transient nucleation,nucleus accretion,multidirectional heterotopic growth,and columnar crystal stacking,and ultimately the formation of a dense deposited layer.In addition,the prepared ultra-thin Mg foil with Mo substrate can stably cycle for 1000 h at 3 mA cm^(-2) with high utilization of 50% in the symmetric cell.This study develops a facile method for the preparation of ultra-thin Mg foils,which opens up a new path for developing high-performance ultra-thin negative electrodes for RMBs.
基金supported by grants from the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Major/key program(No.23M1060280)the Fundamental Research Funds for the Central Universities(No.2232024D-34 and No 2232023A-10).
文摘Magnesium(Mg)alloys are promising candidates for biodegradable implants and medical devices due to their biocompatibility,mechanical properties,and ability to degrade in vivo,thereby eliminating the need for secondary removal surgeries[1,2].However,their clinical adoption is hindered by rapid corrosion in physiological environments[3–5].Due to the high chemical reactivity of magnesium substrates and the inability of primary corrosion degradation products to form ideal protective layers,no effective scientific guidance has yet been identified from fundamental material science to address the rapid degradation of bare Mg[6–8].Surface modification strategies equivalently create new materials wrapped in a matrix,which can thus be extensively explored to enhance the corrosion resistance of Mg alloys while endowing them with tailored biological functionalities[9,10].
基金funded by the National Natural Science Foundation of China(No.51801116 and 52001176)the Shandong Province Key Research and Development Plan(No.2019GHZ019 and 2021SFGC1001)the Youth Innovation and Technology Support Program of Shandong Provincial Colleges and Universities(No.2020KJA002).
文摘With the rapid development of Mg alloys,deeper understanding to the thermodynamic and diffusional kinetic behavior of intermetallic compounds(IMCs)is important for studying the effect of alloying elements to the microstructure evolution.Specially,a systematic quantitative investigation on the diffusional growth of IMCs is of great necessity.However,the works studying the elemental diffusion behaviors of multiple-element IMCs are rare in magnesium alloy systems.The current work takes the ternary Mg-Al-Zn system as research target,and combines the diffusion couple technique,phase stability diagrams,in-situ observation technique and numerical inverse method to investigate the temperature-dependent kinetic coefficients.The parabolic growth constant(PGC)and interdiffusion coefficients for Mg solid-solution phase andγ-Mg_(17)Al_(12),β-Mg_(2)Al_(3),ε-Mg_(23)Al_(30),MgZn_(2),Mg_(2)Zn_(3),τ-Mg_(32)(Zn,Al)49 andφ-Mg_(5)Zn_(2)Al_(2) IMCs in the Mg-Al-Zn alloy system are determined.By comparing the current experimental with calculation results,the rate-controlling factor of the temperature-dependent diffusion growth ofφ,τandεternary IMCs in the Mg-Al-Zn system is further discussed in detail.
基金supported by the Natural Science Founda-tion of Beijing(Grant No.2182017,2202017).
文摘A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid(ILs)during the LePEO process for LA91 magnesium-lithium(Mg-Li)alloy.Results show that the ionic liquid BmimBF_(4)participates in the LePEO coating formation process,causing an increment in coating thickness and surface roughness.The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process(LePEO-IL).After adding BmimBF_(4),corrosion current density decreases from 1.159×10^(−4)A·cm^(−2)to 8.143×10^(−6)A·cm^(−2).The impedance modulus increases to 1.048×10^(4)Ω·cm^(−2)and neutral salt spray remains intact for 24 h.The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid.The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.
基金supported by The National Key Research and Development Program of China(No.2020YFC1107501)National Natural Science Foundation of China(No.51971222),STS program(No.20201600200042)Dong Guan Innovative Research Team Program.Basic applied research program of Liaoning Province of China(No.2022020347-JH2/1013)。
文摘Biodegradable magnesium-matrix composites(BMMCs)added with bone-like compounds such as hydroxyapatite(HA)have promising orthopedic application potential,but the in vivo results of BMMCs are insufficient,and the difference between in vitro and in vivo are not clarified.In this work,Mg-Zn-Nd-Zr/(10/15/20wt%)HA(Ca_(10)(PO_(4))_(6)OH_(2))composites were prepared through friction stirring processing(FSP).It was found that corrosion rate of the composites increased with increase of the HA content,where the corrosion rate from hydrogen evolution of the Mg/10wt%HA was about 0.107 mm/y,showing better corrosion resistance compared with other BMMCs,and the agglomeration of HA powders significantly aggravated the localized corrosion.The ALP specific activity of the MC3T3-E1 cells cultured for14 days with Mg/10wt%HA(2.12 IU/mg)was higher than that of the matrix(1.85 IU/mg),but there was no difference with the FSP group(2.13 IU/mg).In the early implantation of the rabbit femur,bone volume fraction(BV/TV)of Mg/10wt%HA was 10.69,which was higher than that of the FSP group(6.35).The histological staining showed that the Mg/10wt%HA implant was surrounded by more trabecular bone tissue,exhibiting better osteoinductive regeneration.The Mg-Zn-Nd-Zr/HA composites exhibit higher osteogenic activity in vivo differently from in vitro osteogenic expression.
基金support from the Na-tional Key Research and Development Program of China(2021YFC2400703)the Key Projects of the Joint Fund of the National Natural Science Foundation of China(U1804251)support from Natural Science Foundation of Henan Provincial(222300420309).
文摘The degradation behavior of biodegradable Mg alloys has become a research hotspot in the fields about biodegradable metallic materials.While the most of the related publications mainly focused on the degradation rate of Mg-based materials,but rare to care about the changes of their mechanical properties during the immersion period,which can significantly affect their service performance.The link between residual strength and Mg degradation is not appreciated enough.In this work,a series media were constructed based on Hanks’solution,the effects of inorganic ions on the degradation rate and mechanical integrity of Mg-Zn-Y-Nd alloy were investigated.The results indicated that the degradation behavior of Mg alloy was mainly controlled by degradation products and there is no direct correspondence between the degradation rate change and mechanical integrity of Mg alloy.The relevant findings are beneficial for selecting the monitoring index in Mg corrosion tests and evaluating the service reliability of Mg alloys for biomedical applications.
基金supported by the National Natural Science Foundation of China(Grant No.82202672)the Key Research and Development Program of Anhui Province(No.2022e07020017)+5 种基金China Postdoctoral Science Foundation Grant(2022M723049)the National Postdoctoral Program for Innovative Talents(BX20230350)Research Funds of Centre for Leading Medicine and Advanced Technologies of IHM(No.2023IHM02007)the Foundation of National Center for Translational Medicine(Shanghai)SHU Branch(No.SUITM-202301)Anhui Provincial Research Preparation Plan(2022AH040074),Natural science fund for colleges and universities in Anhui Proxince(2023AH053289)Research Fund of Anhui Institute of translational medicine(2022zhyx-C32).
文摘Magnesium-based biomaterials(MBMs)are one of the most promising materials for tissue engineering due to their unique mechanical properties and excellent functional properties.This review describes the development,advantages,and challenges of MBMs for biomedical applications,especially for tissue repair and regeneration.The history of the use of MBMs from the beginning of the 20th century is traced,and the transformative advances in contemporary applications of MBMs in areas such as orthopedics and cardiovascular surgery are emphasized.The review also provides insight into the signaling pathways affected by MBMs,such as the PI3K/Akt and RANKL/RANK/OPG pathways,which are critical for osteogenesis and angiogenesis.The review advocates that future research should focus on optimizing alloy compositions,surface modification and exploring innovative technologies such as 3D printing to improve the efficacy of MBMs in complex tissue repair.The potential of MBMs to tissue engineering and regenerative medicine is significant,urging further exploration and interdisciplinary collaboration to maximize their therapeutic effects.
基金jointly supported by the National Natural Science Foundation of China (Grant Nos: 51704209,51701060,51901153)Natural Science Foundation of Shanxi province (Nos: 201801D121088,201901D211096)the Science and Technology Major Project of Shanxi province (Nos: 20191102007,20191102008)。
文摘The creep properties, microstructural characteristics and creep mechanisms of as-cast Mg-5Bi-5Sn(BT55) alloy without and with Mn(BTM550) addition were investigated via creep at 423, 448, and 473 K as well as stresses of 30, 50 and 75 MPa. The results indicate that adding Mn can result in the formation of primary and the dynamic precipitated α-Mn phases. In addition, the morphology of the precipitated Mg_(3)Bi_(2) phase and the orientation relationship between Mg_(2)Sn precipitates and α-Mg can be effectively modified. Tailoring the microstructural characteristics is responsible for the improved creep performance of BTM550 alloy. The dominant creep mechanisms in BT55 and BTM550 alloys are dislocation cross-slip and climb, respectively. Furthermore, twinning and pyramidal slip play an assisting part in both alloys during creep process.
基金the financial support from the National Natural Science Foundation of China (51875317,52222510)Key Research and Development Program of Shandong Province (2021ZLGX01)。
文摘The tensile tests of the extruded ZK60 Mg containing a longitudinal weld seam were carried out at room and elevated temperatures, and the effects of induced microstructure inhomogeneity on tensile deformation behavior was clarified. The results show that the deformation mode, dynamic recrystallization(DRX), texture evolution and mechanical properties are strongly affected by the longitudinal weld seam,temperature, and loading direction. The room temperature(RT) deformation of welding zone is controlled by the dislocation slips with the association of some twins, while twinning plays significant roles in the accommodation of c-axis strain of the coarse grains on matrix zone.The deformation at RT stretched along extrusion direction(ED) and transverse direction(TD) are controlled by basal slip/twinning and basal slip/prismatic slip/twinning, respectively. During high temperature tension, the dislocation cross slip of pyramidal slip is activated, and grain boundary sliding occurred in welding zone, leading to the superplastic behavior. With the increase of tensile temperature, the predominant DRX mode is transformed from continuous DRX to discontinuous DRX. Moreover, the basal poles of the grains spread from TD towards ED with the decrease of maximum pole intensity when stretched along ED, while non-basal textures are transformed to (10-10) fiber texture when stretched along TD. The slip-dominated flow is seen during RT tension along ED, while twinning becomes predominant during RT tension along TD. The fine grain structure causes the superior RT tensile properties along ED of welding zone with ultimate tensile strength of 315 MPa and elongation to failure of 13.8%. With the increase of tensile temperature, the slipping-dominated deformation is transformed into twinning-dominated, causing the decrease of strength and increase of elongation.
基金supported by“National Natural Science Foundation of China”(Grant Nos.51971078,51871074 and 51671066)“The Project National United Engineering Laboratory for Advanced Bearing Tribology,Henan Univer-sity of Science and Technology”(Grant No.201911).
文摘Converting CO_(2)to valuable materials is attractive in environmental protection and resource utilization.In this study,a vapor-liquid interface reaction system for mass production of high-quality graphene is reported.The graphene obtained has high crystallinity and few defects during the reaction of CO_(2)and Mg melt.The growth mechanism of graphene is demonstrated in vapor-liquid interface area by combining the CO_(2)bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles.The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness.Additionally,the V-L reaction method ingeniously solves the dispersion of graphene in metal,providing a preparation strategy of Mg matrix composites with structure and function integration.
基金The authors express their gratitude to the Deutsche Forschungsgemeinschaft(DFG)for financial support(MO 848/18-2)。
文摘Grain boundaries play a significant role in the deformation of polycrystals.Their response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjoining crystallites by changing their structure and geometry.The current study thus investigates the deformation behaviour of Mg bicrystals with 90°<1120>symmetric tilt boundary strained in plane-strain compression up to different final strains.Due to the initial soft orientation of the two crystals,activation of basal slip in each crystal gave rise to lattice rotation around the transverse direction towards the compression direction of the channel-die.Hundreds of single EBSD maps with a small step size were obtained from the GB region and stitched together to produce large panoramic maps of a macroscopic scale.Although very time-consuming,this technique has proven useful in clarifying the origin of the non-uniform deformation zones in the vicinity of the grain boundary and explains the mechanisms,by which the grain boundary was able to cope with the imposed strain before fracture.Interestingly,several variants of extension twins were observed as an additional deformation mechanism despite having negative Schmid factors.Systematic investigation of their resulting combined shear components with respect to the sample coordinate system revealed an alignment along the longitudinal direction of the channel-die,therefore justifying their nucleation.
基金supported by the National Science Foundation of China(key project grant No.51731008 and general project grant No.51671163).
文摘A novel Mg-Al LDH film was in-situ prepared hydrothermally in an alkaline aqueous solution on an Al-alloyed AZ31 substrate.The structural,chemical and functional characteristics of the film were explored by means of scanning electron microscope(SEM),X-ray diffraction(XRD),energy dispersive spectrometer(EDS),polarization curve,AC impedance and salt immersion tests,respectively.The anti-corrosion results indicated that the Mg-Al LDH film on the Al-alloyed AZ31 surface could effectively protect the AZ31 from corrosion attack even after 90 days of immersion in 3.5 wt.%NaCl solution.The protection performance is surprisingly better than most of the reported coatings on Mg alloys.More interestingly,when the Mg-Al LDH film was scratched,the exposed Al-alloyed surface might gradually release metal ions and re-generate dense LDH nano-sheets in the corrosive environment to inhibit the further corrosion there,exhibiting a self-repairing behavior.The combination of the benign long-term protection and desirable self-repairing performance in this new process of surface-alloying and LDH-formation may significantly extend the practical application of magnesium alloys.
基金the support from Projects of Major Innovation Platforms for Scientific and Technological and Local Transformation of Scientific and Technological Achievements of Xi’an (No.20GXSF0003)the Higher Education Institution Discipline Innovation and Intelligence Base of Shaanxi Provincial (No.S2021-ZC-GXYZ0011)National Natural Science Foundation of China (Grants No.51801154)。
文摘Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time(IDT) in the wire and arc additive manufacturing(WAAM) process of Mg alloy.The thermal couples were used to monitor the thermal history during the WAAM process. Additionally, the effect of different IDTs on the microstructure characteristics and resultant mechanical properties of WAAM-processed Mg alloy thin-wall were investigated. The results showed that the stable temperature of the thin-wall component could reach 290 ℃ at IDT=0s, indicating that the thermal accumulation effect was remarkable. Consequently, unimodal coarse grains with an average size of 39.6 μm were generated, and the resultant room-temperature tensile property was poor. With the IDT extended to 60s, the thermal input and thermal dissipation reached a balance, and the stable temperature was only 170 ℃, closing to the initial temperature of the substrate. A refined grain structure with bimodal size distribution was obtained. The remelting zone had fine grains with the size of 15.2 μm, while the arc zone owned coarse grains with the size of 24.5 μm.The alternatively distributed coarse and fine grains lead to the elimination of strength-ductility trade-off. The ultimate tensile strength and elongation of the samples at IDT=60s are increased by 20.6 and 75.0% of those samples at IDT=0s, respectively. The findings will facilitate the development of additive manufacturing processes for advanced Mg alloys.
基金supported by the Grant of Russian Science Foundation, Russia (project no. 21–73– 10148, https://rscf.ru/en/project/21–73–10148/)The study of material‘s structure, composition, and corrosion processes kinetics was supported by the Grant of Russian Science Foundation, Russia (project no. 20–13–00130, https://rscf.ru/en/project/20–13–00130/)Raman spectra were acquired under the government assignments from the Ministry of Science and Higher Education of the Russian Federation, Russia (project no. FWFN(0205)-2022–0003)。
文摘A new method of the formation of composite coatings with the function of active corrosion protection of magnesium alloys was developed using the plasma electrolytic oxidation(PEO) method. Susceptibility of PEO-layers to pitting formation was evaluated using localized electrochemical methods(SVET/SIET). The morphological features and electrochemical properties of composite coatings were studied using SEM/EDX, XRD, micro-Raman spectroscopy and EIS/PDP measurements, respectively. The effect of surface layers impregnation with corrosion inhibitor on their protective properties in a corrosive environment was established. Additional protection was achieved using controllable coating pore sealing with polymer. It was found that the polymer treatment of the PEO-layer does not reduce the inhibitor’s efficiency. The formed protective composite inhibitor-and-polymer-containing layers decrease the corrosion current density of a magnesium alloy in a 3 wt.% Na Cl solution to three orders of magnitude. This predetermines the prospect of new smart coatings formation that significantly expand the field of application of electrochemically active materials. The mechanism of smart composite coating corrosion degradation was established. The antibacterial activity of the inhibitor-containing coatings against S. aureus methicillin-resistant strain was proved using the in vitro model. These protective layers are promising for reducing the incidence of implant-associated infections.
基金supported by Innovation Research Group of Universities in Chongqing(CXQT21030)Chongqing Talents:Exceptional Young Talents Project(CQYC201905100)Chongqing Youth Expert Studio,Hong Kong Scholars Program。
文摘Grain growth directly influences the plasticity and strength of Mg alloys.As the grain size decreases from the microscale to the nanoscale,the plasticity of Mg alloys continually increases,whereas the strength first increases and later decreases.These trends are observed because the plastic deformation mechanism changes from dislocation–twinning dominance to grain boundary dominance.In this study,the factors influencing grain growth,such as the temperature of plastic deformation/annealing,second-phase particles and solute atoms,are examined to aid effective control of the grain size.Additionally,the mechanisms of grain growth,typically induced by strain and thermal activation,are clarified.Strain-induced grain boundary migration is attributable to the difference in the strain energy stored in adjacent grains with high-density dislocations.Heat-induced grain boundary migration is driven by the difference in the energy of the grain boundary/subgrain boundary and boundary curvature.Abnormal grain growth can be induced by anisotropy of the strain energy,anisotropy of the grain boundary mobility,depinning of the second phase and high misorientation gradient.
基金the State Research Agency(Ministry of Science and Innovation of Spain),the Spanish National Research Council(CSIC)and the European Regional Development Fund(ERDF)for the support under the project RYC2019-027006-I(AEI/FEDER/UE)。
文摘The effect of laser surface melting on the corrosion resistance of AZ31 Mg alloy in 0.1 M NaCl solution was investigated using different laser processing conditions(energy densities of 14 and 17 J cm^(-2)).Laser treatment induced rough surfaces primarily composed of oxidized species of Mg.XPS analysis revealed that the surface concentration of Al increased significantly as a consequence of LSM.Electrochemical impedance spectroscopy showed that the laser treatment remarkably increased the polarization resistance of the AZ31 Mg alloy and induced a passive-like region of about 100 mV,as determined by potentiodynamic polarization.Analysis of the results obtained provide solid evidence that within the immersion times used in this study,LSM treatment increased the corrosion resistance of AZ31 Mg alloy under open circuit conditions and anodic polarization.
