Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic rec...Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic recrystallization(DRX),while twin regions experience rapid recrystallization during static recrystallization(SRX).The activation of twinning can lead to changes in lattice orientation,significantly impacting the final texture in Mg alloys.The active roles of twinning are influenced by various factors during the activation process,and the mobility of twin boundaries(TB)can be amplified by stress effects,dislocation interactions,and thermal effects.Conversely,annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them,restraining their motion.Events such as segregation may also alter the twinning propensity in Magnesium-rare earth(Mg-RE)alloys.While{10–11}contraction twins(CT)and{10–11}-{10–12}double twins(DT)can promote dynamic recrystallization(DRX),they also pose a risk as potential sources of voids and cracks.Additionally,understanding the nucleation and growth mechanisms of twinning is crucial,and these aspects are briefly reviewed in this article.Considering the factors mentioned above,this article summarizes the recent research progress in this field,shedding light on advancements in recent eras.展开更多
In this study,a phase-field scheme that rigorously obeys conservation laws and irreversible thermodynamics is developed for modeling stress-corrosion coupled damage(SCCD).The coupling constitutive relationships of the...In this study,a phase-field scheme that rigorously obeys conservation laws and irreversible thermodynamics is developed for modeling stress-corrosion coupled damage(SCCD).The coupling constitutive relationships of the deformation,phase-field damage,mass transfer,and electrostatic field are derived from the entropy inequality.The SCCD localization induced by secondary phases in Mg is numerically simulated using the implicit iterative algorithm of the self-defined finite elements.The quantitative evaluation of the SCCD of a C-ring is in good agreement with the experimental results.To capture the damage localization,a micro-galvanic corrosion domain is defined,and the buffering effect on charge migration is explored.Three cases are investigated to reveal the effect of localization on corrosion acceleration and provide guidance for the design for resistance to SCCD at the crystal scale.展开更多
Multi-physics thermo-fluid modeling has been extensively used as an approach to understand melt pool dynamics and defect formation as well as optimizing the process-related parameters of laser powder-bed fusion(L-PBF)...Multi-physics thermo-fluid modeling has been extensively used as an approach to understand melt pool dynamics and defect formation as well as optimizing the process-related parameters of laser powder-bed fusion(L-PBF).However,its capabilities for being implemented as a reliable tool for material design,where minor changes in material-related parameters must be accurately captured,is still in question.In the present research,first,a thermo-fluid computational fluid dynamics(CFD)model is developed and validated against experimental data.Considering the predicted material properties of the pure Mg and commercial ZK60 and WE43 Mg alloys,parametric studies are done attempting to elucidate how the difference in some of the material properties,i.e.,saturated vapor pressure,viscosity,and solidification range,can influence the melt pool dynamics.It is found that a higher saturated vapor pressure,associated with the ZK60 alloy,leads to a deeper unstable keyhole,increasing the keyhole-induced porosity and evaporation mass loss.Higher viscosity and wider solidification range can increase the non-uniformity of temperature and velocity distribution on the keyhole walls,resulting in increased keyhole instability and formation of defects.Finally,the WE43 alloy showed the best behavior in terms of defect formation and evaporation mass loss,providing theoretical support to the extensive use of this alloy in L-PBF.In summary,this study suggests an approach to investigate the effect of materials-related parameters on L-PBF melting and solidification,which can be extremely helpful for future design of new alloys suitable for L-PBF.展开更多
Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical applica...Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.展开更多
This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The ext...This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air cooling.The extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during extrusion.Due to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser grains.The AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,respectively.However,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and propagation.During bending,a macrocrack initiates on the outer surface of bending specimen in both alloys.The AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 alloy.The bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the specimen.In bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relationship ofε_(f,bending)=–0.1A_(ppt)+5.86.展开更多
The influence of pre-aging treatment on the microstructure,texture and mechanical properties of the Mg–6Zn–1Gd–1Er(wt.%)alloy was investigated.The microstructure analysis shows that the presence of pre-aging is ben...The influence of pre-aging treatment on the microstructure,texture and mechanical properties of the Mg–6Zn–1Gd–1Er(wt.%)alloy was investigated.The microstructure analysis shows that the presence of pre-aging is beneficial to{1012}twin nucleation at the early stage of extrusion and inhibits the growth of twins and promotes the formation of[1010]-fiber texture components,thus accelerating the complex process of recrystallization.In the middle stage of extrusion,the extruded samples under the condition of solid solution were subjected to dynamic precipitation during severe shear deformation.The precipitation of the second phase particles followed the particle stimulating nucleation(PSN)mechanism,which increased the volume fraction of DRX grains during extrusion.In the extruded samples under the peak-aged condition,the particles appear dissolved during the severe shear deformation strain,which slows down the DRX process.In the later stage of extrusion,the small rod-shaped particles followed the PSN mechanism,and finally formed the strong fiber texture.The extruded alloy exhibits the strongest mechanical properties under the peak-aged state,with ultimate tensile strength(UTS)of 346 MPa,tensile yield strength(TYS)of 217 MPa,and elongation to failure(EL)of 13.6%.The improvement of mechanical properties is mainly attributed to the existence of strong fiber texture,small rod-shaped and block-shaped phases.展开更多
This review paper provides an overview of the micropillar compression technique as applied to magnesium(Mg) and its alloys. It explores the influence of various factors, such as pillar size, shape, temperature, and st...This review paper provides an overview of the micropillar compression technique as applied to magnesium(Mg) and its alloys. It explores the influence of various factors, such as pillar size, shape, temperature, and strain rate on the mechanical properties of Mg.Additionally, the impact of alloying elements, aging, and precipitates in Mg alloys has been extensively examined, revealing their significant influence on mechanical performance. The study highlights the strength and strain hardening improvements in Mg with decreasing pillar size in micropillar compression. Furthermore, the role of precipitates as strengthening agents, affecting deformation mechanisms and overall mechanical response, is explored. These valuable insights are crucial for designing Mg-based materials with enhanced mechanical properties for advanced engineering applications.展开更多
A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compressi...A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compression yield asymmetry,compared with that prepared via room-temperature rotary swaging.Transmission electron microscopy investigations showed that at the initial stage,multiple twins,mostly tension twins,were activated and intersected with each other,thereby refining the coarse grains into a fine lamellar structure.Then,two types of nanoscale subgrains were generated with increasing swaging strain.The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries.This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress.The second type of nanoscale subgrain was formed within the twin lamellae.The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays.Finally,randomly oriented nanograins were obtained via dynamic recrystallization,under the combined function of deformation heat and increased stored energy.Compared with room-temperature rotary swaging,cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.展开更多
Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film prep...Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film preparation technique has emerged in recent years because only pure water is required as the steam source and its environmentally friendly LDH coating fits the current need for green development.Moreover,this coating can effectively inhibit the corrosion of the Mg alloy substrate due to the chemical bonding between the coating and the Mg alloy substrate.This review systematically explains cutting-edge advancements in the growth mechanism and corrosion behavior of LDH steam coatings,and analyzes the advantages and limitations of the steam-coating method.The influencing factors including pressure,CO_(2)/CO_(3)^(2-),aluminum content of the substrate alloy,solution type,and acid-pickling pretreatment,as well as the post-treatment of steam-coating defects,are comprehensively elucidated,providing new insights into the development of the in situ steam-coating technique.Finally,existing issues and future prospects are discussed to further accelerate the widespread application of Mg alloys.展开更多
Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their suscep...Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.展开更多
The effects of Nd addition on the mechanical properties and plastic deformability of AZ71 Mg alloys were investigated.0.5%-2.0%（mass fraction） Nd was added to AZ71 Mg alloys.The grain size and the amount of brittle ...The effects of Nd addition on the mechanical properties and plastic deformability of AZ71 Mg alloys were investigated.0.5%-2.0%（mass fraction） Nd was added to AZ71 Mg alloys.The grain size and the amount of brittle β-Mg17Al12 phase reduce with increasing the Nd addition,while nanosized AlxNdy precipitates form.In combination with 32% rotary forging and subsequent annealing,the grain size of Nd-added AZ71 Mg alloys reduces greatly from over 350 μm to below 30 μm.Both tensile strength and ductility increase with the Nd addition up to 1.0%.The addition of Nd beyond 1.0% leads to the aggregations of rod-shaped Al11Nd3 and blocky Al2 Nd precipitates,thereby deteriorating both strength and ductility.The 1.0% Nd-added AZ71 Mg alloy shows tensile strength up to 253 MPa and elongation of 10.7%.It is concluded that adding 1.0% Nd to AZ71 Mg alloy yields the optimum toughness,whether under as-cast or rotary forging and annealing conditions.展开更多
In the present review,the formation of superhydrophobic(SHP)structures on the surface of Mg alloys was investigated.Different methods including hydrothermal technique,chemical and electrochemical deposition,conversion...In the present review,the formation of superhydrophobic(SHP)structures on the surface of Mg alloys was investigated.Different methods including hydrothermal technique,chemical and electrochemical deposition,conversion and polymer coating,and etching routes were discussed.The superhydrophobicity could form on the surface of Mg alloys by the application of different chemical,electrochemical,and physical methods followed by the immersion of these alloys in the solution containing modifying agents including fatty acids or long-chain molecules.The formed morphology,composition,and contact angle were reported and the effect of synthesis route on these characteristics was reviewed.展开更多
The last decade has seen a significant growth in the market for alloys used for implants,especially for those intended for orthopedic implants.Research into biodegradable magnesium-based alloys has made great strides ...The last decade has seen a significant growth in the market for alloys used for implants,especially for those intended for orthopedic implants.Research into biodegradable magnesium-based alloys has made great strides in this period,so huge progress has been made in their use in the medical industry.The important factors that led to the intensification of research in this regard,were social but also economic,wanting to improve the quality of life,by reducing the use of conventionally permanent metallic implants(stainless steel,cobalt-based alloys,and titanium alloys)which involve the second implant removal surgery and other undesirable effects(stress shielding and metal ion releases),with a negative impact on the emotional and physical condition of patients,and by significantly reducing the costs for both the patient and the health system in the field of orthopedics.This paper refers to the impact and importance of biodegradable Mg alloys,reviewing the beginning of their development,the significant characteristics that make them so desirable for such applications(orthopedic implants)but also the characteristics that must be modulated(corrosion rate and mechanical properties)to arrive at the ideal product for the targeted application.It highlights,in detail,the mechanism and aspects related to the corrosion behaviour of Mg alloys,electrochemical characterization techniques/methods,as well as strategies to improve the corrosion behaviour and mechanical properties of these types of biodegradable alloys.The means of optimization,the category and the effect of the alloying elements,the design criteria,the requirements that the implants of biodegradable alloys Mg-based must meet and the aspects related to their efficiency are also presented.Finally,the potential applications in the specialized clinics,as well as the final products currently used and made by important prestigious companies in the world are approached.展开更多
Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg a...Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.展开更多
Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory ...Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory of singular interface is introduced,which provides the physical base and calculation methodology for interpreting precipitate morphology and orientation relationship(OR),especially useful for understanding irrational facets and ORs.Guided by the theory,recent experimental findings are systematically summarized,including thermally stable and metastable precipitates with various crystal structures.Then,theoretical advances inspired by the findings are introduced,which deepens our understanding on OR selection and preference of irrational facets.At last,future research directions in this field are proposed.展开更多
In this study,four different Mg-Zn-Ca-Mn alloys were produced using gravity die casting method.Mn content was kept constant in all alloys,while Zn and Ca were added in two different ratios.Homogenization heat treatmen...In this study,four different Mg-Zn-Ca-Mn alloys were produced using gravity die casting method.Mn content was kept constant in all alloys,while Zn and Ca were added in two different ratios.Homogenization heat treatment was applied to all cast alloys and a specimen from each homogenized alloy was hot rolled.Microstructure,mechanical properties,and corrosion behavior of the homogenized and hot rolled alloys were investigated as comparatively.Following results were obtained;grain size decreased significantly with increasing Zn content,Zn promoted Ca 2 Mg 6 Zn 3 phase formation,corrosion resistance increased with increasing Zn/Ca atomic ratio,hot rolling resulted in much higher tensile strength but much lower ductility and toughness.Among the homogenized and hot rolled alloys,ZXM300-h alloy(hot rolled ZXM300 alloy)with its 146±2.5 MPa yield strength,229±3.7 MPa tensile strength,%1.6±0.1 elongation and 0.029 mm/yr.immersion corrosion rate exhibited the best mechanical properties and corrosion resistance to be used as a biodegradable alloy such as fracture bone plate material.展开更多
Mg alloys have been regarded as revolutionary metallic biomaterials for biodegradable bone implants,but their applications are mainly blocked by the too rapid degradation in physiological environment.This study explor...Mg alloys have been regarded as revolutionary metallic biomaterials for biodegradable bone implants,but their applications are mainly blocked by the too rapid degradation in physiological environment.This study explores the dual alloying effects of Mn and/or Sn on the performance of Mg alloys prepared by selective laser melting.The observed microstructure indicated remarkable refinement of both the grains and intermetallic phases in the Mn-and/or Sn-containing alloys during the rapid solidification process.Moreover,approximately a half decrease in corrosion rate was observed for AZ61-0.4Mn-0.8Sn alloy with respect to AZ61 alloy.The improved corrosion behavior was primarily due to the enhanced protective effects of surface layers,in which Mn-and/or Sn-rich phases acted as a helpful barrier against medium penetration and thereby alleviated the current exchange with the matrix.In addition,the solute Mn and/or Sn positively shifted the corrosion potential,which also brought about a better corrosion resistance.Furthermore,the strength and hardness of the alloys were also effectively improved and comparable to those of cortical bone.This could be ascribed to the dissolved Mn and/or Sn atoms and the finely dispersed intermetallic phases,which might cause lattice distortion and precipitation hardening.Besides,the Mn-and/or Sn-containing alloys showed good cytocompatibility as indicated by the normal morphology and increased viability of MG-63 cells.These findings suggest that the developed AZ61-Mn-Sn alloy is a promising candidate for biodegradable bone implants.展开更多
Biodegradable magnesium(Mg)alloys exhibit great potential for use as temporary structures in tissue engineering applications.Such degradable implants require no secondary surgery for their removal.In addition,their co...Biodegradable magnesium(Mg)alloys exhibit great potential for use as temporary structures in tissue engineering applications.Such degradable implants require no secondary surgery for their removal.In addition,their comparable mechanical properties with the human bone,together with excellent biocompatibility,make them a suitable candidate for fracture treatments.Nevertheless,some challenges remain.Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue.Among different methods used to improve the performance of the biodegradable Mg alloys to address these challenges,it appears that heat treatment is the most effective way to modify the microstructure and thus the corrosion behavior and mechanical properties without changing the composition or shape of the alloys.A desirable combination of corrosion and mechanical properties can be obtained through a precise control of the heat treatment parameters.In this report,the effects of different heat treatments(T4 and T6)on the microstructure,corrosion behavior,and mechanical properties of some of the most important heat-treatable biodegradable Mg alloys(Mg-Zn,Mg-Gd,Mg-Y,Mg-Nd,Mg-Al and Mg-Ag)are examined as well as new perspectives to enhance their clinical implementation.展开更多
An overview about one thermodynamic database of multi-component Mg alloys is given in this work.This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-compo...An overview about one thermodynamic database of multi-component Mg alloys is given in this work.This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-component(Mg–Ag–Al–Ca–Ce–Cu–Fe–Gd–K–La–Li–Mn–Na–Nd–Ni–Pr–Si–Sn–Sr–Th–Y–Zn–Zr)system.First,the major computational and experimental tools to establish the thermodynamic database of Mg alloys are briefly described.Subsequently,among the investigated binary and ternary systems,representative binary and ternary systems are shown to demonstrate the major feature of the database.Finally,application of the thermodynamic database to solidification simulation and selection of heat treatment schedule is described.展开更多
基金supported by the National Natural Science Foundation of China(No.U22A20187,No.52271147,No.12261160364).
文摘Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic recrystallization(DRX),while twin regions experience rapid recrystallization during static recrystallization(SRX).The activation of twinning can lead to changes in lattice orientation,significantly impacting the final texture in Mg alloys.The active roles of twinning are influenced by various factors during the activation process,and the mobility of twin boundaries(TB)can be amplified by stress effects,dislocation interactions,and thermal effects.Conversely,annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them,restraining their motion.Events such as segregation may also alter the twinning propensity in Magnesium-rare earth(Mg-RE)alloys.While{10–11}contraction twins(CT)and{10–11}-{10–12}double twins(DT)can promote dynamic recrystallization(DRX),they also pose a risk as potential sources of voids and cracks.Additionally,understanding the nucleation and growth mechanisms of twinning is crucial,and these aspects are briefly reviewed in this article.Considering the factors mentioned above,this article summarizes the recent research progress in this field,shedding light on advancements in recent eras.
基金the National Natural Science Foundation of China(Nos.11872216 and 12272192)the Natural Science Foundation of Zhejiang Province(No.LY22A020002)+2 种基金the Natural Science Foundation of Ningbo City(No.202003N4083)the Scientific Research Foundation of Graduate School of Ningbo UniversityNingbo Science and Technology Major Project(No.2022Z002)。
文摘In this study,a phase-field scheme that rigorously obeys conservation laws and irreversible thermodynamics is developed for modeling stress-corrosion coupled damage(SCCD).The coupling constitutive relationships of the deformation,phase-field damage,mass transfer,and electrostatic field are derived from the entropy inequality.The SCCD localization induced by secondary phases in Mg is numerically simulated using the implicit iterative algorithm of the self-defined finite elements.The quantitative evaluation of the SCCD of a C-ring is in good agreement with the experimental results.To capture the damage localization,a micro-galvanic corrosion domain is defined,and the buffering effect on charge migration is explored.Three cases are investigated to reveal the effect of localization on corrosion acceleration and provide guidance for the design for resistance to SCCD at the crystal scale.
基金the financial supports received from Wenner-Gren foundation(UPD2021-0229),JernkontoretSTT(Stiftelsen för Tillämpad Termodynamik).
文摘Multi-physics thermo-fluid modeling has been extensively used as an approach to understand melt pool dynamics and defect formation as well as optimizing the process-related parameters of laser powder-bed fusion(L-PBF).However,its capabilities for being implemented as a reliable tool for material design,where minor changes in material-related parameters must be accurately captured,is still in question.In the present research,first,a thermo-fluid computational fluid dynamics(CFD)model is developed and validated against experimental data.Considering the predicted material properties of the pure Mg and commercial ZK60 and WE43 Mg alloys,parametric studies are done attempting to elucidate how the difference in some of the material properties,i.e.,saturated vapor pressure,viscosity,and solidification range,can influence the melt pool dynamics.It is found that a higher saturated vapor pressure,associated with the ZK60 alloy,leads to a deeper unstable keyhole,increasing the keyhole-induced porosity and evaporation mass loss.Higher viscosity and wider solidification range can increase the non-uniformity of temperature and velocity distribution on the keyhole walls,resulting in increased keyhole instability and formation of defects.Finally,the WE43 alloy showed the best behavior in terms of defect formation and evaporation mass loss,providing theoretical support to the extensive use of this alloy in L-PBF.In summary,this study suggests an approach to investigate the effect of materials-related parameters on L-PBF melting and solidification,which can be extremely helpful for future design of new alloys suitable for L-PBF.
文摘Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.
基金supported by the National Research Foundation of Korea(NRFgrant nos.2019R1A2C1085272 and RS-2023-00244478)funded by the Ministry of Science,ICT,and Future Planning(MSIP,South Korea)。
文摘This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air cooling.The extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during extrusion.Due to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser grains.The AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,respectively.However,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and propagation.During bending,a macrocrack initiates on the outer surface of bending specimen in both alloys.The AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 alloy.The bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the specimen.In bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relationship ofε_(f,bending)=–0.1A_(ppt)+5.86.
基金the financial supports from the National Natural Science Foundation of China(Grant No.51975207&51404079)Hunan Provincial Natural Science Foundation for Excellent Young Scholars of China(Grant No.2019JJ30010)Guangdong Provincial Department of Science and Technology(Grant No.2014B010105009,No.2015A030313902)。
文摘The influence of pre-aging treatment on the microstructure,texture and mechanical properties of the Mg–6Zn–1Gd–1Er(wt.%)alloy was investigated.The microstructure analysis shows that the presence of pre-aging is beneficial to{1012}twin nucleation at the early stage of extrusion and inhibits the growth of twins and promotes the formation of[1010]-fiber texture components,thus accelerating the complex process of recrystallization.In the middle stage of extrusion,the extruded samples under the condition of solid solution were subjected to dynamic precipitation during severe shear deformation.The precipitation of the second phase particles followed the particle stimulating nucleation(PSN)mechanism,which increased the volume fraction of DRX grains during extrusion.In the extruded samples under the peak-aged condition,the particles appear dissolved during the severe shear deformation strain,which slows down the DRX process.In the later stage of extrusion,the small rod-shaped particles followed the PSN mechanism,and finally formed the strong fiber texture.The extruded alloy exhibits the strongest mechanical properties under the peak-aged state,with ultimate tensile strength(UTS)of 346 MPa,tensile yield strength(TYS)of 217 MPa,and elongation to failure(EL)of 13.6%.The improvement of mechanical properties is mainly attributed to the existence of strong fiber texture,small rod-shaped and block-shaped phases.
文摘This review paper provides an overview of the micropillar compression technique as applied to magnesium(Mg) and its alloys. It explores the influence of various factors, such as pillar size, shape, temperature, and strain rate on the mechanical properties of Mg.Additionally, the impact of alloying elements, aging, and precipitates in Mg alloys has been extensively examined, revealing their significant influence on mechanical performance. The study highlights the strength and strain hardening improvements in Mg with decreasing pillar size in micropillar compression. Furthermore, the role of precipitates as strengthening agents, affecting deformation mechanisms and overall mechanical response, is explored. These valuable insights are crucial for designing Mg-based materials with enhanced mechanical properties for advanced engineering applications.
基金Xin Chen,Chuming Liu,Yingchun Wan and Zhiyong Chen acknowledge National Natural Science Foundation of China(Grant number 51574291 and 51874367).
文摘A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compression yield asymmetry,compared with that prepared via room-temperature rotary swaging.Transmission electron microscopy investigations showed that at the initial stage,multiple twins,mostly tension twins,were activated and intersected with each other,thereby refining the coarse grains into a fine lamellar structure.Then,two types of nanoscale subgrains were generated with increasing swaging strain.The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries.This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress.The second type of nanoscale subgrain was formed within the twin lamellae.The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays.Finally,randomly oriented nanograins were obtained via dynamic recrystallization,under the combined function of deformation heat and increased stored energy.Compared with room-temperature rotary swaging,cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.
基金This work was supported by the National Natural Science Foundation of China through the projects 51601108 and 52071191。
文摘Layered double hydroxide(LDH)coatings on magnesium(Mg)alloys shine brightly in the field of corrosion protection because of their special ion-exchange function.State-of-the-art steam coating as a type of LDH film preparation technique has emerged in recent years because only pure water is required as the steam source and its environmentally friendly LDH coating fits the current need for green development.Moreover,this coating can effectively inhibit the corrosion of the Mg alloy substrate due to the chemical bonding between the coating and the Mg alloy substrate.This review systematically explains cutting-edge advancements in the growth mechanism and corrosion behavior of LDH steam coatings,and analyzes the advantages and limitations of the steam-coating method.The influencing factors including pressure,CO_(2)/CO_(3)^(2-),aluminum content of the substrate alloy,solution type,and acid-pickling pretreatment,as well as the post-treatment of steam-coating defects,are comprehensively elucidated,providing new insights into the development of the in situ steam-coating technique.Finally,existing issues and future prospects are discussed to further accelerate the widespread application of Mg alloys.
文摘Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.
基金supported by the Ministry of Science and Technology of Taiwan under research grant No.MOST 103-2221-E-027-009Foxconn Technology Group
文摘The effects of Nd addition on the mechanical properties and plastic deformability of AZ71 Mg alloys were investigated.0.5%-2.0%（mass fraction） Nd was added to AZ71 Mg alloys.The grain size and the amount of brittle β-Mg17Al12 phase reduce with increasing the Nd addition,while nanosized AlxNdy precipitates form.In combination with 32% rotary forging and subsequent annealing,the grain size of Nd-added AZ71 Mg alloys reduces greatly from over 350 μm to below 30 μm.Both tensile strength and ductility increase with the Nd addition up to 1.0%.The addition of Nd beyond 1.0% leads to the aggregations of rod-shaped Al11Nd3 and blocky Al2 Nd precipitates,thereby deteriorating both strength and ductility.The 1.0% Nd-added AZ71 Mg alloy shows tensile strength up to 253 MPa and elongation of 10.7%.It is concluded that adding 1.0% Nd to AZ71 Mg alloy yields the optimum toughness,whether under as-cast or rotary forging and annealing conditions.
文摘In the present review,the formation of superhydrophobic(SHP)structures on the surface of Mg alloys was investigated.Different methods including hydrothermal technique,chemical and electrochemical deposition,conversion and polymer coating,and etching routes were discussed.The superhydrophobicity could form on the surface of Mg alloys by the application of different chemical,electrochemical,and physical methods followed by the immersion of these alloys in the solution containing modifying agents including fatty acids or long-chain molecules.The formed morphology,composition,and contact angle were reported and the effect of synthesis route on these characteristics was reviewed.
基金performed under contracts no.46N/2019-project no.PN19310102/2019 and 30PFE/2018 between the National Institute for Research and Development in Electrical Engineering ICPE-CA and the Romanian Ministry of Research and Innovation
文摘The last decade has seen a significant growth in the market for alloys used for implants,especially for those intended for orthopedic implants.Research into biodegradable magnesium-based alloys has made great strides in this period,so huge progress has been made in their use in the medical industry.The important factors that led to the intensification of research in this regard,were social but also economic,wanting to improve the quality of life,by reducing the use of conventionally permanent metallic implants(stainless steel,cobalt-based alloys,and titanium alloys)which involve the second implant removal surgery and other undesirable effects(stress shielding and metal ion releases),with a negative impact on the emotional and physical condition of patients,and by significantly reducing the costs for both the patient and the health system in the field of orthopedics.This paper refers to the impact and importance of biodegradable Mg alloys,reviewing the beginning of their development,the significant characteristics that make them so desirable for such applications(orthopedic implants)but also the characteristics that must be modulated(corrosion rate and mechanical properties)to arrive at the ideal product for the targeted application.It highlights,in detail,the mechanism and aspects related to the corrosion behaviour of Mg alloys,electrochemical characterization techniques/methods,as well as strategies to improve the corrosion behaviour and mechanical properties of these types of biodegradable alloys.The means of optimization,the category and the effect of the alloying elements,the design criteria,the requirements that the implants of biodegradable alloys Mg-based must meet and the aspects related to their efficiency are also presented.Finally,the potential applications in the specialized clinics,as well as the final products currently used and made by important prestigious companies in the world are approached.
基金The Natural Science Foundation of China under Grant Nos.51922048,51871108 and 51625402Partial financial support came from the Fundamental Research Funds for the Central Universities,JLU,Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09)The Science and Technology Development Program of Jilin Province(No.20200201193JC)。
文摘Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.
基金This project was financially supported by the National Science Foundation of Chongqing(Project no.cstc2018jcyjAX0070)Fundamental Research Funds for the Central Universities(Project No.XDJK2019B003)+1 种基金the National Natural Science Foundation of China(Project no.51601154)The authors are also very grateful to Yanan Chen and Zhiwen Du for checking the language.
基金Financially supported by the Fundamental Research Funds for the Central Universities(Project FRF-TP-19-022A3Z)National Natural Science Foundation of China(Project 51771022)
文摘Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory of singular interface is introduced,which provides the physical base and calculation methodology for interpreting precipitate morphology and orientation relationship(OR),especially useful for understanding irrational facets and ORs.Guided by the theory,recent experimental findings are systematically summarized,including thermally stable and metastable precipitates with various crystal structures.Then,theoretical advances inspired by the findings are introduced,which deepens our understanding on OR selection and preference of irrational facets.At last,future research directions in this field are proposed.
基金This study was supported by the Scientific Research Projects Coordination Unit of Karabuk University.Project Number:KBU-BAP-16/2-DR-100.
文摘In this study,four different Mg-Zn-Ca-Mn alloys were produced using gravity die casting method.Mn content was kept constant in all alloys,while Zn and Ca were added in two different ratios.Homogenization heat treatment was applied to all cast alloys and a specimen from each homogenized alloy was hot rolled.Microstructure,mechanical properties,and corrosion behavior of the homogenized and hot rolled alloys were investigated as comparatively.Following results were obtained;grain size decreased significantly with increasing Zn content,Zn promoted Ca 2 Mg 6 Zn 3 phase formation,corrosion resistance increased with increasing Zn/Ca atomic ratio,hot rolling resulted in much higher tensile strength but much lower ductility and toughness.Among the homogenized and hot rolled alloys,ZXM300-h alloy(hot rolled ZXM300 alloy)with its 146±2.5 MPa yield strength,229±3.7 MPa tensile strength,%1.6±0.1 elongation and 0.029 mm/yr.immersion corrosion rate exhibited the best mechanical properties and corrosion resistance to be used as a biodegradable alloy such as fracture bone plate material.
基金This study was supported by the following funds:(1)The Natural Science Foundation of China(51705540,51935014,51905553,81871494,81871498)Hunan Provincial Nat-ural Science Foundation of China(2018JJ3671,2019J50774,2019JJ50588)+3 种基金JiangXi Provincial Natural Science Foun-dation of China(20192ACB20005)Guangdong Province Higher Vocational Colleges&Schools Pearl River Scholar Funded Scheme(2018)The Open Sharing Fund for the Large-scale Instruments and Equipments of Central South UniversityThe Project of Hunan Provincial Science and Technology Plan(2017RS3008).
文摘Mg alloys have been regarded as revolutionary metallic biomaterials for biodegradable bone implants,but their applications are mainly blocked by the too rapid degradation in physiological environment.This study explores the dual alloying effects of Mn and/or Sn on the performance of Mg alloys prepared by selective laser melting.The observed microstructure indicated remarkable refinement of both the grains and intermetallic phases in the Mn-and/or Sn-containing alloys during the rapid solidification process.Moreover,approximately a half decrease in corrosion rate was observed for AZ61-0.4Mn-0.8Sn alloy with respect to AZ61 alloy.The improved corrosion behavior was primarily due to the enhanced protective effects of surface layers,in which Mn-and/or Sn-rich phases acted as a helpful barrier against medium penetration and thereby alleviated the current exchange with the matrix.In addition,the solute Mn and/or Sn positively shifted the corrosion potential,which also brought about a better corrosion resistance.Furthermore,the strength and hardness of the alloys were also effectively improved and comparable to those of cortical bone.This could be ascribed to the dissolved Mn and/or Sn atoms and the finely dispersed intermetallic phases,which might cause lattice distortion and precipitation hardening.Besides,the Mn-and/or Sn-containing alloys showed good cytocompatibility as indicated by the normal morphology and increased viability of MG-63 cells.These findings suggest that the developed AZ61-Mn-Sn alloy is a promising candidate for biodegradable bone implants.
基金the European Research Council under Grant Agreement No.267464SPDMETALS(TGL)。
文摘Biodegradable magnesium(Mg)alloys exhibit great potential for use as temporary structures in tissue engineering applications.Such degradable implants require no secondary surgery for their removal.In addition,their comparable mechanical properties with the human bone,together with excellent biocompatibility,make them a suitable candidate for fracture treatments.Nevertheless,some challenges remain.Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue.Among different methods used to improve the performance of the biodegradable Mg alloys to address these challenges,it appears that heat treatment is the most effective way to modify the microstructure and thus the corrosion behavior and mechanical properties without changing the composition or shape of the alloys.A desirable combination of corrosion and mechanical properties can be obtained through a precise control of the heat treatment parameters.In this report,the effects of different heat treatments(T4 and T6)on the microstructure,corrosion behavior,and mechanical properties of some of the most important heat-treatable biodegradable Mg alloys(Mg-Zn,Mg-Gd,Mg-Y,Mg-Nd,Mg-Al and Mg-Ag)are examined as well as new perspectives to enhance their clinical implementation.
基金the National Key Research and Development Program of China(No.2016YFB0301101)the project of Innovation-driven plan in Central South University(No.2015CX004)Thermo_calc AB,and National Nature Science Fundation of China(No.50731002).
文摘An overview about one thermodynamic database of multi-component Mg alloys is given in this work.This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-component(Mg–Ag–Al–Ca–Ce–Cu–Fe–Gd–K–La–Li–Mn–Na–Nd–Ni–Pr–Si–Sn–Sr–Th–Y–Zn–Zr)system.First,the major computational and experimental tools to establish the thermodynamic database of Mg alloys are briefly described.Subsequently,among the investigated binary and ternary systems,representative binary and ternary systems are shown to demonstrate the major feature of the database.Finally,application of the thermodynamic database to solidification simulation and selection of heat treatment schedule is described.
