To have a better understand on the change of microstructure via kinetics, the diffusion behavior of Mg alloys is of special interest to researchers. Meanwhile, diffusion coefficients of Mg based alloys can explain and...To have a better understand on the change of microstructure via kinetics, the diffusion behavior of Mg alloys is of special interest to researchers. Meanwhile, diffusion coefficients of Mg based alloys can explain and represent their diffusion behavior well. The evolution of experimental and calculated methods for detecting and extracting diffusion coefficients was discussed briefly. The reasonable diffusion data, especially self-diffusion coefficients, impurity diffusion coefficients and inter-diffusion coefficients of Mg alloys, were reviewed in detail serving to design the Mg alloys with higher accuracy. Then the practical applications of diffusion coefficients of Mg alloys were summarized,including diffusional mobility establishing, precipitation simulation and mechanical properties prediction.展开更多
Magnesium and its related materials have potential applications in the automotive sector for weight reduction,in energy storage technologies such as batteries and hydrogen storage,and in biomedical field due to their ...Magnesium and its related materials have potential applications in the automotive sector for weight reduction,in energy storage technologies such as batteries and hydrogen storage,and in biomedical field due to their biodegradability.In comparison,the researches on the latter ones are currently receiving more and more interests.This paper explores recent research advancements in Mg-based materials in these fields especially within recent 4 years in Germany.展开更多
Previous work indicated that long-period stacking ordered(LPSO) phase and/or γ’ in rare earth containing Mg biomaterials had contradictory mechanisms responsible for their degradation in less complex or standard sal...Previous work indicated that long-period stacking ordered(LPSO) phase and/or γ’ in rare earth containing Mg biomaterials had contradictory mechanisms responsible for their degradation in less complex or standard salt media, such as 0.9 % NaCl solution. They needed to be further investigated in a more realistic simulated body fluid(SBF). The present work investigated the influence of the amount and types of intermetallics on the degradation behavior of as-cast Mg-xDy-Zn(x = 5, 10, 15 wt.%) alloys using immersion test in Dulbecco's modified Eagle's medium(DMEM) + Glutamax together with 10 % Fetal bovine serum(FBS) under cell culture conditions. It was revealed that the existence of intermetallics exhibited different effects on the degradation behavior of alloys. At the early stage of immersion, Mg-10Dy-1.5Zn alloy suffered the most serious degradation among these three alloys, owing to its more severe micro galvanic corrosion. With the immersion proceeding, the degradation rate of Mg-5Dy-1.5Zn alloy consistently increased because of the scattered distribution of few intermetallics. In contrast, the continuous network structure of intermetallics and a compact degradation layer provided protection from further degradation for Mg-10Dy-1.5Zn and Mg-15Dy-1.5Zn alloys. In the as-cast Mg-5Dy-1.5Zn alloy, only small amount of intermetallics composed of W, γ’ and18R LPSO phases acted as galvanic cathodes, accelerating its degradation. With Dy content increasing to 10 and 15 wt.%, large amounts of intermetallics including 18R LPSO and dense γ’ phases were formed, which on the other hand can serve as a continuous network barrier to retard degradation propagation. Finally, the good adhesion and proliferation of the Human umbilical cord perivascular(HUCPV) on the surface of the Mg-10Dy-1.5Zn and Mg-15Dy-1.5Zn alloy indicated their good biocompatibility.展开更多
Biodegradable metals have been of great interest in making gastrointestinal implants these years.The most researched biodegradable metal is magnesium(Mg),followed by zinc(Zn)and iron(Fe).However,due to the limitations...Biodegradable metals have been of great interest in making gastrointestinal implants these years.The most researched biodegradable metal is magnesium(Mg),followed by zinc(Zn)and iron(Fe).However,due to the limitations of in vivo experiments and the complex component of the gastrointestinal fluid,their degradation mechanisms in such an environment are still ambiguous.In this work,the human duodenal fluid(HDF)was used to investigate their in vitro degradation behaviors,with a simulated duodenal fluid(SDF)prepared for the control group based on the HDF ionic composition.After immersion of these metals for 7 days,it is found that HDF shows a stronger p H buffering effect than SDF due to the presence of organics.These organics can also hinder the degradation of metals by affecting their product formation in different ways.On the one hand,the adsorption of organics and their effects on the fluid dominate their degradation inhibition effect on Mg and Zn in HDF.On the other hand,they can hinder the further oxidation of the degradation products of Fe,which is the main mechanism resulting in a lower degradation rate of Fe in HDF rather than in SDF.Among the three metals,Mg unsurprisingly shows the highest degradation rate in both fluids.Interestingly,Zn is nearly immune to degradation in HDF,while it presents typical pitting corrosion in SDF.Compared to their degradation rates in popular pseudo-humoral media(e.g.Hanks’Balanced Salt Solutions,Dulbecco’s modified Eagle’s medium)reported previously,Mg degrades faster,and Zn and Fe more slowly in HDF.The higher in vitro degradation rate of Fe than that of Zn is influenced by oxygen and ions in the degradation environment.展开更多
Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is ...Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.展开更多
Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate th...Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate that grains of the as-cast alloys are gradually refined as Sm content increases. The dominant intermetallic ph^se changes from Mg3Sm to Mg4iSm5 till Sm content exceeds 5.0 wt%. The dynami-cally precipitated intermetallic phase during hot-extrusion in dll Sm-containing alloys is Mg3Sm. The intermetallic particles induced by Sm addition could act as heterogeneous nucleation sites for dynamic recrystallization during hot extrusion. They promoted dynamic recrystallization via the particle stim-ulated nucleation mechanism, and resulted in weakening the basal texture in the as-extruded alloys. Sm addition can significantly enhance the strength of the as-extruded Mg-0.5Zn-0.5Zr alloy at room temperature, with the optimal dosage of 3.5 wt%. The optimal yield strength (YS) and ultimate tensile strength (UTS) are 368 MPa and 383 MPa, which were enhanced by approximately 23.1% and 20.8% com-pared with the Sm-free alloy, respectively. Based on microstructural analysis, the dominant strengthening mechanisms are revealed to be grain boundary strengthening and dispersion strengthening.展开更多
Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys.In this contribution,recent r...Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys.In this contribution,recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design,focusing on Mg-Al,Mg-Zn and Mg-rare earth(RE)systems.The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms,e.g.grain refinement,precipitation and texture hardening effect.Finally,the new alloy design and also the future research of wrought magnesium alloys to improve their mechanical properties are discussed.展开更多
The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increas...The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increase the cost of alloy largely.The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored.The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30%at room temperature.Moreover,these alloys exhibit much better corrosion resistance than AZ31 alloy.The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems.The deformation becomes more homogeneous and the resultant textures after deformation are weakened.展开更多
The dynamic tensile properties and microstructural evolution of an extruded EW75 magnesium alloy deformed at ambient temperature and different high strain rates(from 1000 to 3000 s^(-1))along extrusion direction(ED)we...The dynamic tensile properties and microstructural evolution of an extruded EW75 magnesium alloy deformed at ambient temperature and different high strain rates(from 1000 to 3000 s^(-1))along extrusion direction(ED)were investigated by Split Hopkinson Tension Bar(SHTB).The corresponding deformation mechanisms,texture evolution and microstructure changes were analyzed by optical microscope(OM),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).The results show that the extruded EW75 magnesium alloy along ED exhibits a conventional positive strain rate sensitivity that the dynamic flow stresses increase with in creasing strain rate.Texture measurements show that after dynamic tension,the initial weak texture of extruded EW75 magnesium alloy tansforms to a relatively strong<10-10>//ED texture with increasing strain rates.The microstructural analysis demonstrates that dislocation motion are main deformatin mode to accommodate dynamic tensile deformation at high strain rates.In addition,the interactions of dislocation-dislocation and dislocation-second phase lead to the in crease of flow stress and strain hardening with increasing strain rate.展开更多
The influence of Ce addition on the microstructure and mechanical properties of AM50 magnesium alloy was investigated to improve its mechanical properties.The results show that the addition of Ce to AM50 alloy results...The influence of Ce addition on the microstructure and mechanical properties of AM50 magnesium alloy was investigated to improve its mechanical properties.The results show that the addition of Ce to AM50 alloy results in the grain refinement and the mechanical properties of the Ce-modified AM50 at room and elevated temperatures are remarkably improved.AM50 magnesium alloy containing 1% Ce（mass fraction） shows better refinement and mechanical properties compared with the AM50 magnesium alloy with 0.5% Ce and even AM50 alloy without any Ce.展开更多
Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different l...Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different locations of the samples with as-cast,T4 and T6 heat-treated states,respectively,were investigated.No obvious macro segregation has been detected in the high-quality alloy ingot.The main eutectic structures at all different locations are composed ofα-Mg,Mg3RE-type,Mg5RE-type and LPSO phases.At the edge of ingot,the unusual casting twins including 10-12 extension twins and 10-11 compression twins were observed due to the intensive internal stress.In T4 heat-treated alloy,the micro segregation was eliminated.The remained phases wereα-Mg and LPSO phase.Combined with the remarkable age-hardening response,T6 samples exhibits improved mechanical properties at ambient temperature,which derives from the dense prismaticβ'precipitates and profuse basalγ'precipitates.展开更多
The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rat...The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.展开更多
Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleani...Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleaning.The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments.It increases with the increment of RE content.On the surface of the alloy with T4 treatment the amount of formed hydride REH_(2) is higher.In contrast,the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys.Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water.The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides.展开更多
Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considere...Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding,leading to the improvement of creep properties.Based on this point,adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys.The present investigation,however,shows that the creep properties of binary Mg-Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg_(2)Sn at grain boundaries.That means other possible mechanisms function to affect the creep response.It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries.Based on this observation,new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg-Sn alloys.展开更多
Relationship between precipitation strengthening and creep resistance improvement has been an impor-tant topic for the widespread applications of magnesium alloys.Generally,static precipitation strength-ening through ...Relationship between precipitation strengthening and creep resistance improvement has been an impor-tant topic for the widespread applications of magnesium alloys.Generally,static precipitation strength-ening through thermal stable precipitates would generate satisfactory creep resistance.However,an op-posite example is presented in this work and we propose that the size of precipitates plays a crucial role in controlling the operative creep mechanisms.In addition,the precipitate components along with their crystal structures in the crept Mg-4Al-3Sm-0.4Mn samples with/without pre-aging were thor-oughly studied using Cs aberration-corrected high-angle annular dark-field scanning transmission elec-tron microscopy(HAADF-STEM).Previous aging generates a large density of fine precipitates(<~5 nm)homogeneously distributing in Mg matrix and exhibiting satisfactory strengthening effect.However,the number density of precipitate strings consisting of several or even dozens of relatively coarse precipitates(~10 nm)was significantly decreased at the same time.As revealed in this work,the relatively coarse particles in Mg matrix are much more efficient than the fine precipitates in promoting dislocation climb.Therefore,the rate-controlling mechanisms are transferred from dislocation climb to dislocation slip after previous aging,thus leading to degradation of creep resistance.Moreover,there are mainly five types of precipitates/clusters,namelyβ"-(Al,Mg)3Sm,Al5Sm3,ordered Al-Sm cluster,ordered Al-Mn cluster and ordered/unordered AlMnSm clusters.The crystal structures of the former two precipitates were discussed and the formation mechanisms of the precipitates/clusters were revealed.展开更多
This work explores ceramic additive manufacturing in combination with liquid metal infiltration for the production of degradable interpenetrating phase magnesium/hydroxyapatite(Mg/HA) composites. Material extrusion ad...This work explores ceramic additive manufacturing in combination with liquid metal infiltration for the production of degradable interpenetrating phase magnesium/hydroxyapatite(Mg/HA) composites. Material extrusion additive manufacturing was used to produce stoichiometric,and calcium deficient HA preforms with a well-controlled open pore network, allowing the customization of the topological relationship of the composite. Pure Mg and two different Mg alloys were used to infiltrate the preforms by means of an advanced liquid infiltration method inspired by spark plasma sintering, using a novel die design to avoid the structural collapse of the preform. Complete infiltration was achieved in 8 min, including the time for the Mg melting. The short processing time enabled to restrict the decomposition of HA due to the reducing capacity of liquid Mg. The pure Mg-base composites showed compressive yield strength above pure Mg in cast state. Mg alloy-based composites did not show higher strength than the bare alloys due to grain coarsening, but showed similar mechanical properties than other Mg/HA composites that have significantly higher fraction of metallic phase. The composites showed faster degradation rate under simulated body conditions than the bare metallic component due to the formation of galvanic pairs at microstructural level. Mg dissolved preferentially over HA leaving behind a scaffold after a prolonged degradation period. In turn, the fast production of soluble degradation products caused cell metabolic changes after 24 h of culture with not-diluted material extracts. The topological optimization and reduction of the degradation rate are the topics for future research.展开更多
The present work reports the creep behavior and microstructural evolution of the sand-cast Mg-14Gd-0.4Zr alloy(wt.%) prepared by the differential pressure casting machine. Their compressive creep tests at 250 ℃ were ...The present work reports the creep behavior and microstructural evolution of the sand-cast Mg-14Gd-0.4Zr alloy(wt.%) prepared by the differential pressure casting machine. Their compressive creep tests at 250 ℃ were performed under various applied stresses(i.e., 60, 80 and100 MPa). Among them, the sand-cast Mg-14Gd-0.4Zr samples examined under 250 ℃/80 MPa for 39 and 95 h, respectively, were chosen to systemically analyze their creep mechanisms using high-angle annular dark field-scanning transmission electron microscopy(HAADF-STEM).The obtained results showed that the enhancement of creep resistance can be mainly attributed to the coherent β' and β'_F phases with an alternate distribution, effectively impeding the basal dislocations movement. However, with the creep time increasing, the fine β'+β'_F precipitate chains coarsened and transformed to semi-coherent β_1 phase and even to large incoherent β phase(surrounded by precipitate-free areas) in grain interiors. The precipitate-free zones(PFZs) at grain boundaries(GBs) were formed, and they could expand during creep deformation. Apart from the main cross-slip of basal and prismatic dislocations, type dislocations were activated and tended to distribute near the GBs. The aforementioned phenomena induced the stress concentrations, consequently leading to the increment of the creep strain.展开更多
In this study,the texture evolutions of two Mg materials during tension are explored.In-situ X-ray synchrotron and Visco-Plastic SelfConsistent(VPSC) modeling are employed to investigate the different deformation mode...In this study,the texture evolutions of two Mg materials during tension are explored.In-situ X-ray synchrotron and Visco-Plastic SelfConsistent(VPSC) modeling are employed to investigate the different deformation modes between pure Mg and Mg-15Gd(wt.%) alloy.These two materials with a strong extrusion texture show large different slip/twinning activity behaviors during tensile deformation.The basal(a) slip has the highest contribution to the initial stage of plastic deformation for pure Mg.During the subsequent plastic deformation,the prismatic slip is dominant due to the strong ED//(100) fiber texture.In contrast,the deformation behavior of Mg-15Gd alloy is more complex.Twinning and basal slip are dominant at the early stage of plastic deformation,but further deformation results in the increased activation of prismatic and pyramidal slips.In comparison to pure Mg,the ratios of the critical resolved shear stress(CRSS) between non-basal slip and basal slip of the Mg-15Gd alloy are much lower.展开更多
In order to improve the ductility of commercial WE43 alloy and reduce its cost,a Mg-3Y-2Gd-1Nd-0.4Zr alloy with a low amount of rare earths was developed and prepared by sand casting with a differential pressure casti...In order to improve the ductility of commercial WE43 alloy and reduce its cost,a Mg-3Y-2Gd-1Nd-0.4Zr alloy with a low amount of rare earths was developed and prepared by sand casting with a differential pressure casting system.Its microstructure,mechanical properties and fracture behaviors in the as-cast,solution-treated and as-aged states were evaluated.It is found that the aged alloy exhibited excellent comprehensive mechanical properties owing to the fine dense plate-shapedβ'precipitates formed on prismatic habits during aging at 200℃for 192 hrs after solution-treated at 500℃for 24 hrs.Its ultimate tensile strength,yield strength,and elongation at ambient temperature reach to 319±10 MPa,202±2 MPa and 8.7±0.3%as well as 230±4 MPa,155±1 MPa and 16.0±0.5%at 250℃.The fracture mode of as-aged alloy was transferred from cleavage at room temperature to quasi-cleavage and ductile fracture at the test temperature 300℃.The properties of large-scale components fabricated using the developed Mg-3Y-2Gd-1Nd-0.4Zr alloy are better than those of commercial WE43 alloy,suggesting that the new developed alloy is a good candidate to fabricate the large complex thin-walled components.展开更多
The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete i...The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete intermetallic particles at the grain boundaries for the ZK40,the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions.The CaO was not found in the microstructure.However,Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting.Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40.Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40-Y whereas the localised corrosion was not pronounced for ZK40 or ZK40?CaO alloys.Micro-segregation in theα-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys.The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40-CaO was attributed as the main reason for an improved corrosion resistance for the ZK40-CaO alloy.展开更多
基金financially supported by the China Scholarship Council (Grant No: 202006890008), ChinaScience and Technology Committee of Shanghai (19010500400)+1 种基金the “111” project (D16002)the Independent Research Project of State Key Laboratory of Mechanical Transmissions (Grant No. SKLMT-ZZKT-2021M11)。
文摘To have a better understand on the change of microstructure via kinetics, the diffusion behavior of Mg alloys is of special interest to researchers. Meanwhile, diffusion coefficients of Mg based alloys can explain and represent their diffusion behavior well. The evolution of experimental and calculated methods for detecting and extracting diffusion coefficients was discussed briefly. The reasonable diffusion data, especially self-diffusion coefficients, impurity diffusion coefficients and inter-diffusion coefficients of Mg alloys, were reviewed in detail serving to design the Mg alloys with higher accuracy. Then the practical applications of diffusion coefficients of Mg alloys were summarized,including diffusional mobility establishing, precipitation simulation and mechanical properties prediction.
文摘Magnesium and its related materials have potential applications in the automotive sector for weight reduction,in energy storage technologies such as batteries and hydrogen storage,and in biomedical field due to their biodegradability.In comparison,the researches on the latter ones are currently receiving more and more interests.This paper explores recent research advancements in Mg-based materials in these fields especially within recent 4 years in Germany.
基金the China Scholarship Council for the award of fellowship and funding (nos. 202106890013 and 202206095009)German Academic Exchange Service (DAAD) for the award of fellowship and funding (no. 91870848).
文摘Previous work indicated that long-period stacking ordered(LPSO) phase and/or γ’ in rare earth containing Mg biomaterials had contradictory mechanisms responsible for their degradation in less complex or standard salt media, such as 0.9 % NaCl solution. They needed to be further investigated in a more realistic simulated body fluid(SBF). The present work investigated the influence of the amount and types of intermetallics on the degradation behavior of as-cast Mg-xDy-Zn(x = 5, 10, 15 wt.%) alloys using immersion test in Dulbecco's modified Eagle's medium(DMEM) + Glutamax together with 10 % Fetal bovine serum(FBS) under cell culture conditions. It was revealed that the existence of intermetallics exhibited different effects on the degradation behavior of alloys. At the early stage of immersion, Mg-10Dy-1.5Zn alloy suffered the most serious degradation among these three alloys, owing to its more severe micro galvanic corrosion. With the immersion proceeding, the degradation rate of Mg-5Dy-1.5Zn alloy consistently increased because of the scattered distribution of few intermetallics. In contrast, the continuous network structure of intermetallics and a compact degradation layer provided protection from further degradation for Mg-10Dy-1.5Zn and Mg-15Dy-1.5Zn alloys. In the as-cast Mg-5Dy-1.5Zn alloy, only small amount of intermetallics composed of W, γ’ and18R LPSO phases acted as galvanic cathodes, accelerating its degradation. With Dy content increasing to 10 and 15 wt.%, large amounts of intermetallics including 18R LPSO and dense γ’ phases were formed, which on the other hand can serve as a continuous network barrier to retard degradation propagation. Finally, the good adhesion and proliferation of the Human umbilical cord perivascular(HUCPV) on the surface of the Mg-10Dy-1.5Zn and Mg-15Dy-1.5Zn alloy indicated their good biocompatibility.
基金supported by the Science and Technology Project of Jiangsu Province(BE2023719)the Suzhou Science and Technology Project(SYC2022136,SJC2023005,SZS2023023)+2 种基金Nanjing Science and Technology Project(202309015)the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials(AMM2024A01,AMM2023B03)Jiangsu Key Laboratory for Light Metal Alloys(LMA202403)。
文摘Biodegradable metals have been of great interest in making gastrointestinal implants these years.The most researched biodegradable metal is magnesium(Mg),followed by zinc(Zn)and iron(Fe).However,due to the limitations of in vivo experiments and the complex component of the gastrointestinal fluid,their degradation mechanisms in such an environment are still ambiguous.In this work,the human duodenal fluid(HDF)was used to investigate their in vitro degradation behaviors,with a simulated duodenal fluid(SDF)prepared for the control group based on the HDF ionic composition.After immersion of these metals for 7 days,it is found that HDF shows a stronger p H buffering effect than SDF due to the presence of organics.These organics can also hinder the degradation of metals by affecting their product formation in different ways.On the one hand,the adsorption of organics and their effects on the fluid dominate their degradation inhibition effect on Mg and Zn in HDF.On the other hand,they can hinder the further oxidation of the degradation products of Fe,which is the main mechanism resulting in a lower degradation rate of Fe in HDF rather than in SDF.Among the three metals,Mg unsurprisingly shows the highest degradation rate in both fluids.Interestingly,Zn is nearly immune to degradation in HDF,while it presents typical pitting corrosion in SDF.Compared to their degradation rates in popular pseudo-humoral media(e.g.Hanks’Balanced Salt Solutions,Dulbecco’s modified Eagle’s medium)reported previously,Mg degrades faster,and Zn and Fe more slowly in HDF.The higher in vitro degradation rate of Fe than that of Zn is influenced by oxygen and ions in the degradation environment.
文摘Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.
基金supported financially by the National Natural Science Foundation of China (Nos. 51701200 and 21601017)the Project for Science & Technology Development of Jilin Province (Nos. 2016YHZ0006, 20170414001GH, 20180520004JH and 20180520160JH)
文摘Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate that grains of the as-cast alloys are gradually refined as Sm content increases. The dominant intermetallic ph^se changes from Mg3Sm to Mg4iSm5 till Sm content exceeds 5.0 wt%. The dynami-cally precipitated intermetallic phase during hot-extrusion in dll Sm-containing alloys is Mg3Sm. The intermetallic particles induced by Sm addition could act as heterogeneous nucleation sites for dynamic recrystallization during hot extrusion. They promoted dynamic recrystallization via the particle stim-ulated nucleation mechanism, and resulted in weakening the basal texture in the as-extruded alloys. Sm addition can significantly enhance the strength of the as-extruded Mg-0.5Zn-0.5Zr alloy at room temperature, with the optimal dosage of 3.5 wt%. The optimal yield strength (YS) and ultimate tensile strength (UTS) are 368 MPa and 383 MPa, which were enhanced by approximately 23.1% and 20.8% com-pared with the Sm-free alloy, respectively. Based on microstructural analysis, the dominant strengthening mechanisms are revealed to be grain boundary strengthening and dispersion strengthening.
文摘Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys.In this contribution,recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design,focusing on Mg-Al,Mg-Zn and Mg-rare earth(RE)systems.The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms,e.g.grain refinement,precipitation and texture hardening effect.Finally,the new alloy design and also the future research of wrought magnesium alloys to improve their mechanical properties are discussed.
文摘The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increase the cost of alloy largely.The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored.The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30%at room temperature.Moreover,these alloys exhibit much better corrosion resistance than AZ31 alloy.The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems.The deformation becomes more homogeneous and the resultant textures after deformation are weakened.
基金The authors would like to thank Professor Kui Zhang,Beijing General Research Institute for Nonferrous Metal,for providing EW75 magnesium alloy for this work and acknowledge the funding from the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.17KJD430006)Scientific and Technological Innovation Team Foundation of Wuxi Institute of Technology(No.30593118001)Scientific Research Project of Wuxi Institute of Technology(No.ZK201901).The help of EBSD experiment provided by Yukyung Shin from Helmholtz-Zentrum Geesthacht is gratefully acknowledged.
文摘The dynamic tensile properties and microstructural evolution of an extruded EW75 magnesium alloy deformed at ambient temperature and different high strain rates(from 1000 to 3000 s^(-1))along extrusion direction(ED)were investigated by Split Hopkinson Tension Bar(SHTB).The corresponding deformation mechanisms,texture evolution and microstructure changes were analyzed by optical microscope(OM),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).The results show that the extruded EW75 magnesium alloy along ED exhibits a conventional positive strain rate sensitivity that the dynamic flow stresses increase with in creasing strain rate.Texture measurements show that after dynamic tension,the initial weak texture of extruded EW75 magnesium alloy tansforms to a relatively strong<10-10>//ED texture with increasing strain rates.The microstructural analysis demonstrates that dislocation motion are main deformatin mode to accommodate dynamic tensile deformation at high strain rates.In addition,the interactions of dislocation-dislocation and dislocation-second phase lead to the in crease of flow stress and strain hardening with increasing strain rate.
基金Financial support from Turkey Council of Higher Education(YOK) Scholarship for Faruk's PhD Study in Helmholtz-Zentrum Geesthacht HZG is also appreciated
文摘The influence of Ce addition on the microstructure and mechanical properties of AM50 magnesium alloy was investigated to improve its mechanical properties.The results show that the addition of Ce to AM50 alloy results in the grain refinement and the mechanical properties of the Ce-modified AM50 at room and elevated temperatures are remarkably improved.AM50 magnesium alloy containing 1% Ce（mass fraction） shows better refinement and mechanical properties compared with the AM50 magnesium alloy with 0.5% Ce and even AM50 alloy without any Ce.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301100)the Natural Science Foundation Commission of China(Nos.51571044 and 51874062)+2 种基金the Chongqing foundation and advanced research project(No.cstc2019jcyjzdxmX0010)the Fundamental Research Funds for the Central Universities(Nos.2018CDGFCL0005 and 2019CDXYCL0031)the financial support from the China Scholarship Council(No.201906050113)。
文摘Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different locations of the samples with as-cast,T4 and T6 heat-treated states,respectively,were investigated.No obvious macro segregation has been detected in the high-quality alloy ingot.The main eutectic structures at all different locations are composed ofα-Mg,Mg3RE-type,Mg5RE-type and LPSO phases.At the edge of ingot,the unusual casting twins including 10-12 extension twins and 10-11 compression twins were observed due to the intensive internal stress.In T4 heat-treated alloy,the micro segregation was eliminated.The remained phases wereα-Mg and LPSO phase.Combined with the remarkable age-hardening response,T6 samples exhibits improved mechanical properties at ambient temperature,which derives from the dense prismaticβ'precipitates and profuse basalγ'precipitates.
基金supported by the National Key R&D Program of China(No.2021YFB3701100)the National Natural Science Foundation of China(No.52271091)the China Scholarship Council(No.202206050135)。
文摘The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.
文摘Mg–RE(Dy,Gd,Y)alloys show promising for being developed as biodegradable medical applications.It is found that the hydride REH_(2) could be formed on the surface of samples during their preparations with water cleaning.The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments.It increases with the increment of RE content.On the surface of the alloy with T4 treatment the amount of formed hydride REH_(2) is higher.In contrast,the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys.Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water.The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides.
文摘Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding,leading to the improvement of creep properties.Based on this point,adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys.The present investigation,however,shows that the creep properties of binary Mg-Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg_(2)Sn at grain boundaries.That means other possible mechanisms function to affect the creep response.It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries.Based on this observation,new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg-Sn alloys.
基金Chinese Academy of Sciences Youth Innovation Promotion Association(No.2023234)Scientific and Technological Developing Scheme of Jilin Province(No.20220402012GH)+2 种基金National Natural Science Foundation of China(No.U21A20323)Capital Construction Fund within the Budget of Jilin Province(No.2023C044-2)Major science and technology projects of Jilin Province and Changchun City(No.20220301026GX),the Special high-tech。
文摘Relationship between precipitation strengthening and creep resistance improvement has been an impor-tant topic for the widespread applications of magnesium alloys.Generally,static precipitation strength-ening through thermal stable precipitates would generate satisfactory creep resistance.However,an op-posite example is presented in this work and we propose that the size of precipitates plays a crucial role in controlling the operative creep mechanisms.In addition,the precipitate components along with their crystal structures in the crept Mg-4Al-3Sm-0.4Mn samples with/without pre-aging were thor-oughly studied using Cs aberration-corrected high-angle annular dark-field scanning transmission elec-tron microscopy(HAADF-STEM).Previous aging generates a large density of fine precipitates(<~5 nm)homogeneously distributing in Mg matrix and exhibiting satisfactory strengthening effect.However,the number density of precipitate strings consisting of several or even dozens of relatively coarse precipitates(~10 nm)was significantly decreased at the same time.As revealed in this work,the relatively coarse particles in Mg matrix are much more efficient than the fine precipitates in promoting dislocation climb.Therefore,the rate-controlling mechanisms are transferred from dislocation climb to dislocation slip after previous aging,thus leading to degradation of creep resistance.Moreover,there are mainly five types of precipitates/clusters,namelyβ"-(Al,Mg)3Sm,Al5Sm3,ordered Al-Sm cluster,ordered Al-Mn cluster and ordered/unordered AlMnSm clusters.The crystal structures of the former two precipitates were discussed and the formation mechanisms of the precipitates/clusters were revealed.
基金supported by the Czech Science Foundation (grant 19-22662S)Czech Nano Lab project LM2018110 funded by MEYS CR is gratefully acknowledged for the support of the measurements at CEITEC Nano Research Infrastructure+2 种基金MCL acknowledges to Brno Ph.D. Talent scholarship and to the Brno University of Technology Internal Project: CEITEC VUT-J-19-5915SDT acknowledges to CONACYTSNI and SIP-IPN (SAPPI 20220438)LV acknowledges to project no. NU20-08-00150 (MH, Czechia)。
文摘This work explores ceramic additive manufacturing in combination with liquid metal infiltration for the production of degradable interpenetrating phase magnesium/hydroxyapatite(Mg/HA) composites. Material extrusion additive manufacturing was used to produce stoichiometric,and calcium deficient HA preforms with a well-controlled open pore network, allowing the customization of the topological relationship of the composite. Pure Mg and two different Mg alloys were used to infiltrate the preforms by means of an advanced liquid infiltration method inspired by spark plasma sintering, using a novel die design to avoid the structural collapse of the preform. Complete infiltration was achieved in 8 min, including the time for the Mg melting. The short processing time enabled to restrict the decomposition of HA due to the reducing capacity of liquid Mg. The pure Mg-base composites showed compressive yield strength above pure Mg in cast state. Mg alloy-based composites did not show higher strength than the bare alloys due to grain coarsening, but showed similar mechanical properties than other Mg/HA composites that have significantly higher fraction of metallic phase. The composites showed faster degradation rate under simulated body conditions than the bare metallic component due to the formation of galvanic pairs at microstructural level. Mg dissolved preferentially over HA leaving behind a scaffold after a prolonged degradation period. In turn, the fast production of soluble degradation products caused cell metabolic changes after 24 h of culture with not-diluted material extracts. The topological optimization and reduction of the degradation rate are the topics for future research.
基金the Shanghai Sailing Program (23YF1417100)National Natural Science Foundation of China (U2037601)China Scholarship Council (Grant No: 202006890008) for the financial support。
文摘The present work reports the creep behavior and microstructural evolution of the sand-cast Mg-14Gd-0.4Zr alloy(wt.%) prepared by the differential pressure casting machine. Their compressive creep tests at 250 ℃ were performed under various applied stresses(i.e., 60, 80 and100 MPa). Among them, the sand-cast Mg-14Gd-0.4Zr samples examined under 250 ℃/80 MPa for 39 and 95 h, respectively, were chosen to systemically analyze their creep mechanisms using high-angle annular dark field-scanning transmission electron microscopy(HAADF-STEM).The obtained results showed that the enhancement of creep resistance can be mainly attributed to the coherent β' and β'_F phases with an alternate distribution, effectively impeding the basal dislocations movement. However, with the creep time increasing, the fine β'+β'_F precipitate chains coarsened and transformed to semi-coherent β_1 phase and even to large incoherent β phase(surrounded by precipitate-free areas) in grain interiors. The precipitate-free zones(PFZs) at grain boundaries(GBs) were formed, and they could expand during creep deformation. Apart from the main cross-slip of basal and prismatic dislocations, type dislocations were activated and tended to distribute near the GBs. The aforementioned phenomena induced the stress concentrations, consequently leading to the increment of the creep strain.
基金sponsored by the China Postdoctoral Science Foundation (Grant No. 2020M673156)Shanghai Pujiang Program (Grant No. 20PJ1404900)。
文摘In this study,the texture evolutions of two Mg materials during tension are explored.In-situ X-ray synchrotron and Visco-Plastic SelfConsistent(VPSC) modeling are employed to investigate the different deformation modes between pure Mg and Mg-15Gd(wt.%) alloy.These two materials with a strong extrusion texture show large different slip/twinning activity behaviors during tensile deformation.The basal(a) slip has the highest contribution to the initial stage of plastic deformation for pure Mg.During the subsequent plastic deformation,the prismatic slip is dominant due to the strong ED//(100) fiber texture.In contrast,the deformation behavior of Mg-15Gd alloy is more complex.Twinning and basal slip are dominant at the early stage of plastic deformation,but further deformation results in the increased activation of prismatic and pyramidal slips.In comparison to pure Mg,the ratios of the critical resolved shear stress(CRSS) between non-basal slip and basal slip of the Mg-15Gd alloy are much lower.
基金This work was funded by the National Natural Science Foundation of China(No.U2037601 and No.52074183)The authors appreciate Ge Chen,Wenbin Zou as well as Shiwei Wang for preparing the alloys,Wenyu Liu as well as Xuehao Zheng from ZKKF(Beijing)Science&Technology Co.,Ltd for the TEM measurement,Gert Wiese as well as Petra Fischer for SEM and hardness measurement and Yunting Li from the Instrument Analysis Center of Shanghai Jiao Tong University(China)for SEM measurement.Lixiang Yang also gratefully thanks the China Scholarship Council(201906230111)for awarding a fellowship to support his study stay at Helmholtz-Zentrum Geesthacht.
文摘In order to improve the ductility of commercial WE43 alloy and reduce its cost,a Mg-3Y-2Gd-1Nd-0.4Zr alloy with a low amount of rare earths was developed and prepared by sand casting with a differential pressure casting system.Its microstructure,mechanical properties and fracture behaviors in the as-cast,solution-treated and as-aged states were evaluated.It is found that the aged alloy exhibited excellent comprehensive mechanical properties owing to the fine dense plate-shapedβ'precipitates formed on prismatic habits during aging at 200℃for 192 hrs after solution-treated at 500℃for 24 hrs.Its ultimate tensile strength,yield strength,and elongation at ambient temperature reach to 319±10 MPa,202±2 MPa and 8.7±0.3%as well as 230±4 MPa,155±1 MPa and 16.0±0.5%at 250℃.The fracture mode of as-aged alloy was transferred from cleavage at room temperature to quasi-cleavage and ductile fracture at the test temperature 300℃.The properties of large-scale components fabricated using the developed Mg-3Y-2Gd-1Nd-0.4Zr alloy are better than those of commercial WE43 alloy,suggesting that the new developed alloy is a good candidate to fabricate the large complex thin-walled components.
基金the Alexander von Humboldt foundation for the provision of financial support in the form of post-doctoral fellowship
文摘The microstructures of as-cast ZK40,ZK40 with 2%(mass fraction)CaO and ZK40 with 1%(mass fraction)Y were investigated,and the intermetallic phase morphology and the distribution were characterised.By having discrete intermetallic particles at the grain boundaries for the ZK40,the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions.The CaO was not found in the microstructure.However,Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting.Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40.Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40-Y whereas the localised corrosion was not pronounced for ZK40 or ZK40?CaO alloys.Micro-segregation in theα-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys.The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40-CaO was attributed as the main reason for an improved corrosion resistance for the ZK40-CaO alloy.
