Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy wa...Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.展开更多
In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion ...In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.展开更多
A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Micr...A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Microscopy(TEM).The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg_(11-x)Zn_(x)Sr phase belonged to tetragonal I41/amd space group and had the Cd_(11)Ba prototype.The Mg atoms were successfully doped into Zn_(11)Sr crystal lattice by occupying Zn atomic sites.Moreover,the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg_(11-x)Zn_(x)Sr compound.The elastic constants and modulus of the Mg_(11-x)Zn_(x)Sr compounds calculated by first-principles calculations(FPC)indicated they were increased with the increasing of Zn content.The variation of hardness,D-band widths and the total density of states for Mg_(11-x)Zn_(x)Sr compounds with Zn content was discussed.展开更多
As implanted bone fixation materials,magnesium(Mg)alloys have significant advantages because the density and elastic modulus are closest to those of the human bone and they can bio-degrade in the physiological environ...As implanted bone fixation materials,magnesium(Mg)alloys have significant advantages because the density and elastic modulus are closest to those of the human bone and they can bio-degrade in the physiological environment.However,Mg alloys degrade too rapidly and uncontrollably thus hampering clinical adoption.In this study,a highly corrosion-resistant zinc-phosphate-doped micro-arc oxidation(MAO)coating is prepared on the AZ31B alloy,and the degradation process is assessed in vitro.With increasing zinc phosphate concentrations,both the corrosion potentials and charge transfer resistance of the AZ31B alloy coated with MAO coatings increase gradually,while the corrosion current densities di-minish gradually.Immersion tests in the simulated body fluid(SBF)reveal that the increased zinc phos-phate concentration in MAO coating decreases the degradation rate,consequently reducing the release rates of Mg^(2+)and OH-in the physiological micro-environment,which obtains the lowest weight loss of only 5.22%after immersion for 56 days.Effective regulation of degradation provides a weak alkaline environment that is suitable for long-term cell growth and subsequent promotion of bone proliferation,differentiation,mineralization,and cytocompatibility.In addition,the zinc-phosphate-doped MAO coat-ings show an improved wear resistance as manifested by a wear rate of only 3.81 x 10^(-5) mm^(3) N^(-1) m^(-1).The results reveal a suitable strategy to improve the properties of biodegradable Mg alloys to balance tissue healing with mechanical degradation.展开更多
The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR...The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR),the broken I-phase particles are aggregated at theα-Mg/β-Li phase interfaces.However,the cross-rolling(CR)process can not only severely break the bulk I-phase,but also cause the obviously uniform distribution of I-phase particles in the matrix phases.Moreover,the average grain size of the CR samples is 3.61μm and about 50%that of the UR samples.The maximum texture intensities ofα-Mg andβ-Li phases in the CR samples are slightly stronger than those in the UR samples.Tensile results demonstrate that the CR process can effectively enhance the tensile properties and remarkably reduce the mechanical anisotropy of the alloy.For the UR samples,the yield strength,ultimate tensile strength,and elongation ratio along the rolling direction(RD)are 164 MPa,198 MPa,and 16.4%,whereas those along the transverse direction(TD)are 157 MPa,185 MPa,and 22.0%,respectively.For the CR samples,their mechanical properties are basically the same and the mechanical anisotropy is almost eliminated.The yield strength,ultimate tensile strength,and elongation ratio along the cross-rolling direction 1(CRD1)and 2(CRD2)are respectively measured to be 181 MPa and 182 MPa,220 MPa and 218 MPa,20.6%and 20.7%.Failure analysis indicates that for the UR samples being tensile tested along the RD and TD,microcracks are preferentially initiated in the region of aggregated I-phase particles.For the CR samples being tensile tested along both two cross-rolling directions,the initiation of micro-cracks mainly occurs at the I-phase/matrix phase interfaces and in the interior of matrix phases.展开更多
Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure...Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure ensured the 330℃/4 h samples having a good combination of tensile strength and plasticity.Failure analysis demonstrated that for the as-rolled and 330℃/1 h samples with fine grain structure,their plastic deformation was mainly attributed to basal slips,whereas the deformation mechanism in the bimodal grain-structured samples was dominated by basal slips in fine grains and twinning in coarse grains.For the 330℃/8 h samples with coarse grain structure,high densities of twins were activated.Meanwhile,basal slips occurred in the twinned and un-twinned areas of coarse grains and could pass through twin boundaries.For differently treated samples,cracking preferentially occurred along slip bands,resulting in their transgranular fractures.展开更多
By performing the immersion,hydrogen evolution and electrochemical corrosion testing in a 0.1 mol/L NaCl solution,the corrosion performance of differently oriented samples cut from an as-rolled Mg-8wt.%Li alloy plate ...By performing the immersion,hydrogen evolution and electrochemical corrosion testing in a 0.1 mol/L NaCl solution,the corrosion performance of differently oriented samples cut from an as-rolled Mg-8wt.%Li alloy plate has been investigated and compared.It demonstrated that obvious anisotropy in corrosion resistance existed between the sample surfaces with different orientations.Among them,the corrosion rate of"ND"(the normal direction)samples with their surfaces perpendicular to the normal direction of the plate was the highest.The corrosion rate of"TD"(the transverse direction)samples with their surfaces perpendicular to the transverse direction of the plate took the second place.For the"RD"(the rolling direction)samples with their surfaces perpendicular to the rolling direction of the plate,they had the lowest corrosion rate.For all the samples,their corrosion performance and the pitting severity were mainly ascribed to the crystallographic texture ofα-Mg matrix phases because the formed surface films onβ-Li phases could provide good protection to the substrate.For the"ND"and"TD"samples,the exposed surfaces were composed of{0002},{1010}and{1120}planes ofα-Mg phases and subsequently resulted in their severe corrosion attack due to the corrosion couples between basal and prism planes.Since the crystallographic planes of exposedα-Mg phases on the surfaces of"RD"samples were mainly{1010}and{1120}prism planes,the pitting severity was the weakest.展开更多
Through investigating and comparing microstructure and crystallographic texture of as-extruded Mg-14Li and Mg-14Li-6Zn-1Y(in wt%)alloys,the differences in their mechanical anisotropy were investigated.It revealed that...Through investigating and comparing microstructure and crystallographic texture of as-extruded Mg-14Li and Mg-14Li-6Zn-1Y(in wt%)alloys,the differences in their mechanical anisotropy were investigated.It revealed that the formation of I-phase(Mg3Zn6Y,icosahedral structure)can effectively refine grain size.Moreover,compared with Mg-14Li alloy,the texture type of Mg-14Li-6Zn-1Y alloy changed slightly,but its texture intensity decreased remarkably.As a result,the stronger texture contributed to the"normal"mechanical anisotropy of Mg-14Li alloy with higher tensile strength and a lower elongation ratio along transverse direction(TD)than those along extrusion direction(ED).However,for Mg-14Li-6Zn-1Y alloy,the zonal distribution of I-phase particles along ED caused"abnormal"mechanical anisotropy,i.e.higher tensile strength and better plasticity along ED.展开更多
The effect of hydro gen charging on microstructural evolution and corrosion behavior of a Ti-4Al-2V-1Mo-1Fe alloy in a 3.5 wt.% NaCl solution was investigated.The results showed that the hydrogen charging induced the ...The effect of hydro gen charging on microstructural evolution and corrosion behavior of a Ti-4Al-2V-1Mo-1Fe alloy in a 3.5 wt.% NaCl solution was investigated.The results showed that the hydrogen charging induced the formation and growth of γ-TiH and δ-TiH_(2) phases,leading to the initiation and propagation of hydrogen-induced cracks.It was also found that hydrogen charging can change the passivity of this alloy and increase its pitting corrosion susceptibility.The main reason for these was attributed to the fo rmation of hydrides in α phase in the Ti-4Al-2V-1Mo-1Fe alloy,leading to the preferential dissolution of the α phase and thus the deterioration in the protective ability of passive film.展开更多
Both the solid solution and precipitation are mainly strengthening mechanism for the magnesium-based alloys. A great number of alloying elements can be dissolved into the Mg matrix to form the solutes and precipitates...Both the solid solution and precipitation are mainly strengthening mechanism for the magnesium-based alloys. A great number of alloying elements can be dissolved into the Mg matrix to form the solutes and precipitates.Moreover, the type of precipitates varies with different alloying elements and heat treatments, which makes it quite difficult to understand the formation mechanism of the precipitates in Mg-based alloys in depth. Thus, it is very hard to give a systematical regularity in precipitation process for the Mg-based alloys. This review is mainly focused on the formation and microstructural evolution of the precipitates, as a hot topic for the past few years, including Guinier-Preston Zones, quasicrystals and long-period stacking ordered phases formed in a number of Mg-TM-RE alloy systems, where TM = Al, Zn, Zr and RE = Y,Gd, Hd, Ce and La.展开更多
High corrosion kinetics and localised corrosion progress are the primary concerns arising from the clinical implementation of magnesium(Mg)based implantable devices.In this study,a binary Mglithium(Li)alloy consisting...High corrosion kinetics and localised corrosion progress are the primary concerns arising from the clinical implementation of magnesium(Mg)based implantable devices.In this study,a binary Mglithium(Li)alloy consisting a record high Li content of 14%(in weight)was employed as model material aiming to yield homogenous and slow corrosion behaviour in a simulated body fluid,i.e.minimum essential medium(MEM),in comparison to that of generic Mg alloy AZ31 and biocompatible Mg-0.5Zn-0.5Ca counterparts.Scanning electron microscopy examination reveals single-phase microstructural characteristics of Mg-14Li(b-Li),whilst the presence of insoluble phases,cathodic to a-Mg matrix,in AZ31 and Mg-0.5Zn-0.5Ca.Though slight differences exist in the corrosion kinetics of all the specimens over a short-term time scale(no longer than 60 min),as indicated by potentiodynamic polarisation and electrochemical impedance spectroscopy,profound variations are apparent in terms of immersion tests,i.e.mass loss and hydrogen evolution measurements(up to 7 days).Cross-sectional micrographs unveil severe pitting corrosion in AZ31 and Mg-0.5Zn-0.5Ca,but not the case for Mg-14Li.X-ray diffraction patterns and X-ray photoelectron spectroscopy confirm that a compact film(25 mm in thickness)consisting of lithium carbonate(Li2CO3)and calcium hydroxide was generated on the surface of Mg-14Li in MEM,which contributes greatly to its low corrosion rate.It is proposed therefore that the single-phase structure and formation of protective and defect-free Li2CO3 film give rise to the controlled and homogenous corrosion behaviour of Mg-14Li in MEM,providing new insights for the exploration of biodegradable Mg materials.展开更多
In this study,the corrosion behaviors of an as-extruded Mg–4%Zn–2%Y–1.8%Nd(in wt.%)alloy in different physiological saline solutions were investigated and compared.The results indicated that the alloy in the 9 g/L ...In this study,the corrosion behaviors of an as-extruded Mg–4%Zn–2%Y–1.8%Nd(in wt.%)alloy in different physiological saline solutions were investigated and compared.The results indicated that the alloy in the 9 g/L NaCl had the higher corrosion resistance than that containing with CaCl_(2) and NaHCO3.Moreover,it demonstrated that the corrosion behaviors of the alloy in two types of solutions were all dependent on the pre-immersion time.In the 9 g/L NaCl solution,the corrosion current densities of the alloy decreased firstly with the pre-immersion time being<4 h and then increased with the pre-immersion time prolonging from 4 to 48 h.However,in the 9 g/L NaCl solution containing with CaCl_(2) and NaHCO3,the corrosion current density of the alloy exhibited the adverse trend with the prolonging the pre-immersion time.Failure analysis demonstrated that the changes of corrosion resistance in two solutions were mainly dominated by the constituents formed in surface films.展开更多
In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn （AZ31） bar in a simulated body fluid of phosphate buffer saline （PBS） medium was investigated and compared,...In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn （AZ31） bar in a simulated body fluid of phosphate buffer saline （PBS） medium was investigated and compared, and the effect of crystallographic texture on corrosion resistance of the alloy was deeply described. The results showed that at the early stage of immersion, a layer of compact and flat film formed easily on surfaces of both oriented samples. With prolonged immersion time, the degradation of formed corrosive films started and their severity was quite sensitive to the composed crystallographic planes of sample surfaces. For the surface containing highly concentrated orientation of {10-10} and {11-20} prism planes, the degradation of formed corrosive film was quite slight and only occurred at some particular sites even after immersion for 48 h. Thus, the film could keep good corrosive protection to the under- neath substrate. However, for the surface containing [0002} basal planes, {10-10} and {11-20} prism planes, the degradation of corrosive production film occurred widely, resulting in further decrease in the corrosion resistance of immersed samples,展开更多
基金the National Natural Science Foundation of China Projects under Grant[Nos.51871211,U21A2049,52071220,51701129 and 51971054]Liaoning Province’s project of"Revitalizing Liaoning Talents"(XLYC1907062)+10 种基金the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS-200)the Strategic New Industry Development Special Foundation of Shenzhen(JCYJ20170306141749970)the funds of International Joint Laboratory for Light AlloysLiaoning Bai Qian Wan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)National Key Research and Development Program of China under Grant[Nos.2017YFB0702001 and 2016YFB0301105]the Innovation Fund of Institute of Metal Research(IMR)Chinese Academy of Sciences(CAS)the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205the Fundamental Research Fund for the Central Universities under Grant[No.N2009006]Bintech-IMR R&D Program[No.GYY-JSBU-2022-009]。
文摘Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.
基金supported by the 2022 Shenzhen sustainable supporting funds for colleges and universities(20220810143642004)Shenzhen Basic Research Project(JCYJ20200109144608205 and JCYJ20210324120001003)+5 种基金Peking University Shenzhen Graduate School Research Startup Fund of Introducing Talent(No.1270110273)Shenzhen postdoctoral research fund project after outbound(No.2129933651)Shenzhen-Hong Kong Research and Development Fund(No.SGDX20201103095406024)City University of Hong Kong Strategic Research Grants(SRG)(Nos.7005264 and 7005505)Guangdong-Hong Kong Technology Cooperation Funding Scheme(TCFS)(No.GHP/085/18SZ)IER Foundation(IERF2020001 and IERF2019002).
文摘In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.
基金the National Key Research and Development Program of China(grant numbers 2018YFC1106702)the Natural Science Foundation of Guangdong Province,China(grant numbers 2020A1515011301,2018A0303100018 and 2018A030313950)+1 种基金Shenzhen Basic Research Project(grant numbers JCYJ20170815153143221,JCYJ20200109144608205 and JCYJ20170815153210359)IER Foundation(HT-JD-CXY-201902 and HT-JD-CXY201907)for financial support
文摘A new ternary compound,Mg_(11-x)Zn_(x)Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy(SEM),Energy-Dispersive Spectroscope(EDS),X-Ray Diffraction(XRD)and Transmission Electron Microscopy(TEM).The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg_(11-x)Zn_(x)Sr phase belonged to tetragonal I41/amd space group and had the Cd_(11)Ba prototype.The Mg atoms were successfully doped into Zn_(11)Sr crystal lattice by occupying Zn atomic sites.Moreover,the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg_(11-x)Zn_(x)Sr compound.The elastic constants and modulus of the Mg_(11-x)Zn_(x)Sr compounds calculated by first-principles calculations(FPC)indicated they were increased with the increasing of Zn content.The variation of hardness,D-band widths and the total density of states for Mg_(11-x)Zn_(x)Sr compounds with Zn content was discussed.
基金Shenzhen-Hong Kong Research and Development Fund(No.SGDX20201103095406024)2022 Shenzhen Sustainable Supporting Funds for Colleges and Universities(No.20220810143642004)+9 种基金Shenzhen Basic Research Project(Nos.JCYJ20200109144608205 and JCYJ20210324120001003)Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515011301 and 2021A1515012246)Peking University Shenzhen Graduate School Research Start-up Fund of Introducing Talent(No.1270110273)Shenzhen Postdoctoral Research Fund Project after Outbound(No.2129933651)China Postdoctoral Science Foundation(No.2023M730032)City University of Hong Kong Strategic Research Grants(SRG)(7005505)City University of Hong Kong Donation Research Grants(No.9220061 and DON-RMG No.9229021)Guangdong-Hong Kong Technology Cooperation Funding Scheme(TCFS)(No.GHP/085/18SZ)Shenzhen-Hong Kong Technology Cooperation Funding Scheme(TCFS)(No.GHP/149/20SZ and CityU 9440296)IER Foundation(Nos.IERF2020001 and IERF202102).
文摘As implanted bone fixation materials,magnesium(Mg)alloys have significant advantages because the density and elastic modulus are closest to those of the human bone and they can bio-degrade in the physiological environment.However,Mg alloys degrade too rapidly and uncontrollably thus hampering clinical adoption.In this study,a highly corrosion-resistant zinc-phosphate-doped micro-arc oxidation(MAO)coating is prepared on the AZ31B alloy,and the degradation process is assessed in vitro.With increasing zinc phosphate concentrations,both the corrosion potentials and charge transfer resistance of the AZ31B alloy coated with MAO coatings increase gradually,while the corrosion current densities di-minish gradually.Immersion tests in the simulated body fluid(SBF)reveal that the increased zinc phos-phate concentration in MAO coating decreases the degradation rate,consequently reducing the release rates of Mg^(2+)and OH-in the physiological micro-environment,which obtains the lowest weight loss of only 5.22%after immersion for 56 days.Effective regulation of degradation provides a weak alkaline environment that is suitable for long-term cell growth and subsequent promotion of bone proliferation,differentiation,mineralization,and cytocompatibility.In addition,the zinc-phosphate-doped MAO coat-ings show an improved wear resistance as manifested by a wear rate of only 3.81 x 10^(-5) mm^(3) N^(-1) m^(-1).The results reveal a suitable strategy to improve the properties of biodegradable Mg alloys to balance tissue healing with mechanical degradation.
基金supported by the National Natural Science Foundation of China Projects under Grant(Nos.52071220,U21A2049,51871211,51701129,and 51971054)China Postdoctoral Science Foundation(No.2023M733572)+7 种基金Liaoning Province’s project of“Revitalizing Liaoning Talents”(No.XLYC1907062)the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS-200)High level achievement construction project of Shenyang Ligong University(No.SYLUXM202105)Liaoning BaiQianWan Talents Program,the Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220118)National Key Research and Development Program of China under Grant(Nos.2017YFB0702001 and 2016YFB0301105)the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS),the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205the Fundamental Research Fund for the Central Universities under Grant(No.N2009006)Bintech-IMR R&D Program(No.GYY-JSBU-2022–009).
文摘The microstructure and mechanical performance of the unidirectionally and cross-directionally rolled Mg-8Li-6Zn-1Y(in wt.%)sheets have been investigated and compared.It reveals that after the unidirectional rolling(UR),the broken I-phase particles are aggregated at theα-Mg/β-Li phase interfaces.However,the cross-rolling(CR)process can not only severely break the bulk I-phase,but also cause the obviously uniform distribution of I-phase particles in the matrix phases.Moreover,the average grain size of the CR samples is 3.61μm and about 50%that of the UR samples.The maximum texture intensities ofα-Mg andβ-Li phases in the CR samples are slightly stronger than those in the UR samples.Tensile results demonstrate that the CR process can effectively enhance the tensile properties and remarkably reduce the mechanical anisotropy of the alloy.For the UR samples,the yield strength,ultimate tensile strength,and elongation ratio along the rolling direction(RD)are 164 MPa,198 MPa,and 16.4%,whereas those along the transverse direction(TD)are 157 MPa,185 MPa,and 22.0%,respectively.For the CR samples,their mechanical properties are basically the same and the mechanical anisotropy is almost eliminated.The yield strength,ultimate tensile strength,and elongation ratio along the cross-rolling direction 1(CRD1)and 2(CRD2)are respectively measured to be 181 MPa and 182 MPa,220 MPa and 218 MPa,20.6%and 20.7%.Failure analysis indicates that for the UR samples being tensile tested along the RD and TD,microcracks are preferentially initiated in the region of aggregated I-phase particles.For the CR samples being tensile tested along both two cross-rolling directions,the initiation of micro-cracks mainly occurs at the I-phase/matrix phase interfaces and in the interior of matrix phases.
基金supported financially by the Project from the Strategic New Industry Development Special Foundation of Shenzhen (No.JCYJ20170306141749970)National Natural Science Foundation of China Projects under Grant [Nos.51871211 and 51701129]+2 种基金the funds of International Joint Laboratory for Light Alloys,the National Key Research and Development Program of China under Grant [No.2017YFB0702001]Liaoning BaiQianWan Talents Programthe Innovation Fund of Institute of Metal Research (IMR),Chinese Academy of Sciences (CAS)
文摘Through investigating and comparing the mechanical behavior of an as-rolled Mg-3%Al-1%Zn(wt%)alloy before and after annealing treatments,it was revealed that the formation of annealing-tailored bimodal grain structure ensured the 330℃/4 h samples having a good combination of tensile strength and plasticity.Failure analysis demonstrated that for the as-rolled and 330℃/1 h samples with fine grain structure,their plastic deformation was mainly attributed to basal slips,whereas the deformation mechanism in the bimodal grain-structured samples was dominated by basal slips in fine grains and twinning in coarse grains.For the 330℃/8 h samples with coarse grain structure,high densities of twins were activated.Meanwhile,basal slips occurred in the twinned and un-twinned areas of coarse grains and could pass through twin boundaries.For differently treated samples,cracking preferentially occurred along slip bands,resulting in their transgranular fractures.
基金financially supported by the National Key Research and Development Program of China under Grant(Nos.2017YFB0702001 and 2016YFB0301105)the Strategic New Industry Development Special Foundation of Shenzhen(No.JCYJ20170306141749970)+5 种基金the National Natural Science Foundation of China Projects under Grant(Nos.51871211 and 51701129)the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS-200)the funds of International Joint Laboratory for Light Alloys,Liaoning BaiQianWan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220118)the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS)the National Basic Research Program of China(“973 Program”)(No.2013CB632205)。
文摘By performing the immersion,hydrogen evolution and electrochemical corrosion testing in a 0.1 mol/L NaCl solution,the corrosion performance of differently oriented samples cut from an as-rolled Mg-8wt.%Li alloy plate has been investigated and compared.It demonstrated that obvious anisotropy in corrosion resistance existed between the sample surfaces with different orientations.Among them,the corrosion rate of"ND"(the normal direction)samples with their surfaces perpendicular to the normal direction of the plate was the highest.The corrosion rate of"TD"(the transverse direction)samples with their surfaces perpendicular to the transverse direction of the plate took the second place.For the"RD"(the rolling direction)samples with their surfaces perpendicular to the rolling direction of the plate,they had the lowest corrosion rate.For all the samples,their corrosion performance and the pitting severity were mainly ascribed to the crystallographic texture ofα-Mg matrix phases because the formed surface films onβ-Li phases could provide good protection to the substrate.For the"ND"and"TD"samples,the exposed surfaces were composed of{0002},{1010}and{1120}planes ofα-Mg phases and subsequently resulted in their severe corrosion attack due to the corrosion couples between basal and prism planes.Since the crystallographic planes of exposedα-Mg phases on the surfaces of"RD"samples were mainly{1010}and{1120}prism planes,the pitting severity was the weakest.
基金supported financially by the Strategic New Industry Development Special Foundation of Shenzhen (No. JCYJ20170306141749970)the National Natural Science Foundation of China (Nos.51871211 and 51701129)+3 种基金the Natural Science Foundation of Guangdong Province (No.2018A030313950)the funds of International Joint Laboratory for Light Alloys,the National Key Research and Development Program of China (Nos. 2017YFB0702001 and 2016YFB0301105)Liaoning BaiQianWan Talents Programthe Innovation Fund of Institute of Metal Research (IMR),Chinese Academy of Sciences (CAS)
文摘Through investigating and comparing microstructure and crystallographic texture of as-extruded Mg-14Li and Mg-14Li-6Zn-1Y(in wt%)alloys,the differences in their mechanical anisotropy were investigated.It revealed that the formation of I-phase(Mg3Zn6Y,icosahedral structure)can effectively refine grain size.Moreover,compared with Mg-14Li alloy,the texture type of Mg-14Li-6Zn-1Y alloy changed slightly,but its texture intensity decreased remarkably.As a result,the stronger texture contributed to the"normal"mechanical anisotropy of Mg-14Li alloy with higher tensile strength and a lower elongation ratio along transverse direction(TD)than those along extrusion direction(ED).However,for Mg-14Li-6Zn-1Y alloy,the zonal distribution of I-phase particles along ED caused"abnormal"mechanical anisotropy,i.e.higher tensile strength and better plasticity along ED.
基金financially supported by the National Natural Science Foundation of China(Nos.51871211,51871225 and 51701129)。
文摘The effect of hydro gen charging on microstructural evolution and corrosion behavior of a Ti-4Al-2V-1Mo-1Fe alloy in a 3.5 wt.% NaCl solution was investigated.The results showed that the hydrogen charging induced the formation and growth of γ-TiH and δ-TiH_(2) phases,leading to the initiation and propagation of hydrogen-induced cracks.It was also found that hydrogen charging can change the passivity of this alloy and increase its pitting corrosion susceptibility.The main reason for these was attributed to the fo rmation of hydrides in α phase in the Ti-4Al-2V-1Mo-1Fe alloy,leading to the preferential dissolution of the α phase and thus the deterioration in the protective ability of passive film.
基金supported by National Natural Science Fundation of China (Nos. 51171192 and51271183)National Basic Research Program of China(No. 2013CB632205)Innovation Fund of Institute of Metal Research (IMR), Chinese Academy of Sciences(CAS)
文摘Both the solid solution and precipitation are mainly strengthening mechanism for the magnesium-based alloys. A great number of alloying elements can be dissolved into the Mg matrix to form the solutes and precipitates.Moreover, the type of precipitates varies with different alloying elements and heat treatments, which makes it quite difficult to understand the formation mechanism of the precipitates in Mg-based alloys in depth. Thus, it is very hard to give a systematical regularity in precipitation process for the Mg-based alloys. This review is mainly focused on the formation and microstructural evolution of the precipitates, as a hot topic for the past few years, including Guinier-Preston Zones, quasicrystals and long-period stacking ordered phases formed in a number of Mg-TM-RE alloy systems, where TM = Al, Zn, Zr and RE = Y,Gd, Hd, Ce and La.
基金the financial support from the Australian Research Council(ARC)through Linkage scheme(LP150100343)C.L.is supported by China Scholarship Council(CSC).
文摘High corrosion kinetics and localised corrosion progress are the primary concerns arising from the clinical implementation of magnesium(Mg)based implantable devices.In this study,a binary Mglithium(Li)alloy consisting a record high Li content of 14%(in weight)was employed as model material aiming to yield homogenous and slow corrosion behaviour in a simulated body fluid,i.e.minimum essential medium(MEM),in comparison to that of generic Mg alloy AZ31 and biocompatible Mg-0.5Zn-0.5Ca counterparts.Scanning electron microscopy examination reveals single-phase microstructural characteristics of Mg-14Li(b-Li),whilst the presence of insoluble phases,cathodic to a-Mg matrix,in AZ31 and Mg-0.5Zn-0.5Ca.Though slight differences exist in the corrosion kinetics of all the specimens over a short-term time scale(no longer than 60 min),as indicated by potentiodynamic polarisation and electrochemical impedance spectroscopy,profound variations are apparent in terms of immersion tests,i.e.mass loss and hydrogen evolution measurements(up to 7 days).Cross-sectional micrographs unveil severe pitting corrosion in AZ31 and Mg-0.5Zn-0.5Ca,but not the case for Mg-14Li.X-ray diffraction patterns and X-ray photoelectron spectroscopy confirm that a compact film(25 mm in thickness)consisting of lithium carbonate(Li2CO3)and calcium hydroxide was generated on the surface of Mg-14Li in MEM,which contributes greatly to its low corrosion rate.It is proposed therefore that the single-phase structure and formation of protective and defect-free Li2CO3 film give rise to the controlled and homogenous corrosion behaviour of Mg-14Li in MEM,providing new insights for the exploration of biodegradable Mg materials.
基金supported by the National Key Research and Development Program of China under Grant(Nos.2017YFB0702001 and 2016YFB0301105)the Liaoning Province’s project of“Revitalizing Liaoning Talents”(XLYC1907062)+7 种基金the National Natural Science Foundation of China Projects under Grant(Nos.51871211 and 51701129)the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS200)the Strategic New Industry Development Special Foundation of Shenzhen(JCYJ20170306141749970)the funds of the International Joint Laboratory for Light Alloysthe Liaoning BaiQianWan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS)the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205。
文摘In this study,the corrosion behaviors of an as-extruded Mg–4%Zn–2%Y–1.8%Nd(in wt.%)alloy in different physiological saline solutions were investigated and compared.The results indicated that the alloy in the 9 g/L NaCl had the higher corrosion resistance than that containing with CaCl_(2) and NaHCO3.Moreover,it demonstrated that the corrosion behaviors of the alloy in two types of solutions were all dependent on the pre-immersion time.In the 9 g/L NaCl solution,the corrosion current densities of the alloy decreased firstly with the pre-immersion time being<4 h and then increased with the pre-immersion time prolonging from 4 to 48 h.However,in the 9 g/L NaCl solution containing with CaCl_(2) and NaHCO3,the corrosion current density of the alloy exhibited the adverse trend with the prolonging the pre-immersion time.Failure analysis demonstrated that the changes of corrosion resistance in two solutions were mainly dominated by the constituents formed in surface films.
基金supported by the National Natural Science Foundation of China under Grant Nos.51271183 and 51301172the National Basic Research Program of China(973 Program)under Grant No.2013CB632205+1 种基金the Innovation Fund of Institute of Metal Research(IMR)Chinese Academy of Sciences(CAS)
文摘In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn （AZ31） bar in a simulated body fluid of phosphate buffer saline （PBS） medium was investigated and compared, and the effect of crystallographic texture on corrosion resistance of the alloy was deeply described. The results showed that at the early stage of immersion, a layer of compact and flat film formed easily on surfaces of both oriented samples. With prolonged immersion time, the degradation of formed corrosive films started and their severity was quite sensitive to the composed crystallographic planes of sample surfaces. For the surface containing highly concentrated orientation of {10-10} and {11-20} prism planes, the degradation of formed corrosive film was quite slight and only occurred at some particular sites even after immersion for 48 h. Thus, the film could keep good corrosive protection to the under- neath substrate. However, for the surface containing [0002} basal planes, {10-10} and {11-20} prism planes, the degradation of corrosive production film occurred widely, resulting in further decrease in the corrosion resistance of immersed samples,
