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Inhibiting effect of I-phase formation on the plastic instability of the duplex structured Mg-8Li-6Zn-1.2Y(in wt.%)alloy

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镁合金学报(英文) 2023年第6期11卷 2196-2204页

作者： B.J.Wang d.k.xu X.Q.Zhuang L.Y.Sheng School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang110159China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China Peking University Shenzhen InstituteShenzhen Key Lab Human Tissue Regenerate&RepairShenzhen 518057China

In this work,the tensile behaviors of Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys at ambient temperature were investigated and compared.It revealed that the plastic instability of Mg-8%Li alloy was quite remarkable and the variation range of serrated flowing stress can reach5 MPa.For the Mg-8%Li-6%Zn-1.2%Y alloy,the formation of I-phase(Mg_(3)Zn_(6)Y)can simultaneously enhance the tensile strength and eliminate the plastic instability phenomenon,whilst its ductility was degraded.The in-situ tensile tests revealed that for the Mg-8%Li alloy,the severity and number of slip traces present in bothα-Mg andβ-Li matrix phases increased remarkably with the applied tensile strain.However,slip traces were quite fine inβ-Li matrix phase and could be clearly observed when the applied tensile strain exceeded 18%.due to the incompatibility of plastic deformation occurred in two matrix phases,the induced strain concentration atα-Mg/β-Li interfaces caused their subsequent cracking.For the Mg-8%-6%Zn-1.2%Y alloy,the I-phase distributed atα-Mg/β-Li interfaces suppressed the plastic deformation ofα-Mg matrix phase and the tensile strain was dominated by theβ-Li matrix phase,resulting in the disappearance of plastic instability.Moreover,the plastic strain would preferentially concentrate at I-phase/β-Li interfaces and subsequently induced the cracking of I-phase.

关键词： Mg-li alloys Microstructure Plastic deformation Basal slip Cracking

Relationship between the fatigue behavior and grain structures of an as-extruded Mg-6.2%Zn-0.6%Zr(in wt.%)alloy

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Journal of Materials Science & Technology 2023年第18期149卷 119-126页

作者： B.J.Wang d.k.xu C.L.Jiang L.Y.Sheng E.H.Han School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang 110159China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Binzhou Institute of Technology Binzhou 256606China Shandong key Laboratory of Advanced Aluminium Materials and Technology Binzhou 256606China Shenzhen Institute Shenzhen Key Lab Human Tissue Regenerate&RepairPeking UniversityShenzhen 518057China

Through investigating the tension-tension fatigue behavior of an as-extruded Mg-6.2 wt.%Zn-0.6 wt.%Zr(Zk60)alloy,it revealed that the determined fatigue strength at 107 cycles was quite sensitive to the grain structure.Among them,the fine grain structure had the highest fatigue strength of 130 MPa,whereas the typical“bi-modal”grain structure had the lowest fatigue strength of 110 MPa.Failure analysis demon-strated that for the fine grain structure,fatigue cracks preferentially nucleated at grain boundaries.For the“bi-modal”and coarse grain structures,the fatigue crack initiation was dominated by the cracking along slip bands.

关键词： Mg alloys Grain structure Cyclic slips Fatigue behavior Crack initiation

Recent progress in fatigue behavior of Mg alloys in air and aqueous media: A review

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Journal of Materials Science & Technology 2017年第10期33卷 1075-1086页

作者： B.J.Wang S.d.Wang d.k.xu E.H.Han School of Environmental and Chemical Engineering Shenyang Ligong University CAS key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences

due to the interactions between mechanics and chemistry, Mg alloys are inevitably subjected to the combined effect of corrosion attack and cyclic loading, which eventually leads to corrosion fatigue failure. In this paper, fundamental aspects regarding the fatigue behavior of Mg alloys have been reviewed,including：（1） fatigue behavior of Mg alloys in air and aqueous media; and（2） the influence of microstructure, anodic dissolution, hydrogen embrittlement（HE）, heat treatment and surface protection on fatigue behavior of Mg alloys. Moreover, some remaining unresolved issues and future targets to deeply understand the failure mechanism of corrosion fatigue have been described.

关键词： Magnesium alloys Fatigue Corrosion fatigue Crack initiation Hydrogen embrittlement

Effect of corrosion product films on the in vitro degradation behavior of Mg-3%Al-1%Zn(in wt%) alloy in Hank's solution

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Journal of Materials Science & Technology 2018年第10期34卷 1756-1764页

作者： B.J.Wang d.k.xu J.H.dong W.ke School of Environmental and Chemical Engineering Shenyang Ligong University CAS key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Environmental Corrosion Center Institute of Metal Research Chinese Academy of Sciences

Through investigating the corrosion behavior of an as-extruded Mg-3wt%gAl-lwt%Zn （AZ31） alloy in a simulated physiological fluid of Hank＇s solution, it demonstrates that the corrosion process was depen- dent on the immersion time. Further analyses revealed that the highest corrosion resistance could be obtained at 24 h due to the formation of a compact layer of corrosion products on the sample surface. With increasing the immersion time to up to 48 h, the thickness of surface films increased gradually but obvious de-bonding of such film from the substrate could take place, resulting in a certain resilience of the overall corrosion resistance.

关键词： Magnesium Surface layer Corrosion product Interface

Influence of the lithium content on the negative difference effect of Mg-Li alloys

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Journal of Materials Science & Technology 2020年第22期54卷 138-145页

作者： C.Q.Li d.k.xu Z.R.Zhang E.H.Han School of Materials and Energy Guangdong University of TechnologyGuangzhou 510006China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The so-called 'negative difference effect'(NdE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NdE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NdE prior to anodic dissolution as that of conventional Mg alloys.However,the emergence of β-Li phase weakened the NdE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NdE for Mg-4 Li and Mg-7.5 Li alloys.Furthermore,the NdE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.

关键词： Mg-Li alloy Negative difference effect Electrochemical property Corrosion Anodic dissolution

Fatigue crack initiation of magnesium alloys under elastic stress amplitudes:A review

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Frontiers of Mechanical Engineering 2019年第1期14卷 113-127页

作者： B.J.WANG d.k.xu S.d.WANG E.H.HAN School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang 110159China CAS key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The most advantageous property of magnesium(Mg)alloys is their density,which is lower compared with traditional metallic materials.Mg alloys,considered the lightest metallic structural material among others,have great potential for applications as secondary load components in the transportation and aerospace industries.The fatigue evaluation of Mg alloys under elastic stress amplitudes is very important in ensuring their service safety and reliability.Given their hexagonal close packed structure,the fatigue crack initiation of Mg and its alloys is closely related to the deformation mechanisms of twiuning and basal slips.However,for Mg alloys with shrinkage porosities and inclusions,fatigue cracks will preferentially initiate at these defects,remarkably reducing the fatigue lifetime.In this paper,some fundamental aspects about the fatigue crack initiation mechanisms of Mg alloys are reviewed,in cluding the 3 followings:1)Fatigue crack initiation of as-cast Mg alloys,2)influence of microstructure on fatigue crack initiation of wrought Mg alloys,and 3)the effect of heat treatment on fatigue initiation mechanisms.Moreover,some unresolved issues and future target on the fatigue crack initiation mechanism of Mg alloys are also described.

关键词： Mg alloys fatigue behavior microstructure crack initiation deformation mechanism

Effect of Icosahedral Phase on Crystallographic Texture and Mechanical Anisotropy of Mg–4%Li Based Alloys

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Journal of Materials Science & Technology 2017年第5期33卷 475-480页

作者： C.Q.Li d.k.xu S.Yu L.Y.Sheng E.H.Han School of Materials Science and Engineering Northeastern University CAS key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering Shenyang Aerospace University Shenzhen Institute Peking University Shenzhen Key Lab Human Tissue Regenerate & Repair

Through investigating and comparing the microstructure and mechanical properties of the as-extruded Mg alloys Mg-4%Li and Mg-4%Li-6%Zn-l.2%Y （in wt%）, it demonstrates that although the formation of I-phase （Mg3Zn6Y, icosahedral structure） could weaken the crystallographic texture and improve the me- chanical strength, the mechanical anisotropy in terms of strength remains in Mg-4%Li-6%Zn-1.2%Y alloy. Failure analysis indicates that for the Mg-4%Li alloy, the fracture surfaces of the tensile samples tested along transverse direction （Td） contain a large number of plastic dimples, whereas the fracture surface exhibits quasi-cleavage characteristic when tensile samples were tested along extrusion direction （Ed）. For the Mg-4%Li-6%Zn-I.2%Y alloy, typical ductile fracture surfaces can be observed in both ＂Td＂ and ＂Ed＂ samples. Moreover, due to the zonal distribution of broken l-phase particles, the fracture surface of ＂Td＂ samples is characterized by the typical ＂woody fracture＂.

关键词： Mg-Li alloy Texture Mechanical anisotropy Fracture

Effect of rolling ratios on the microstructural evolution and corrosion performance of an as-rolled Mg-8wt.%Li alloy

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Journal of Magnesium and Alloys 2021年第2期9卷 560-568页

作者： B.J.Wang d.k.xu X.Cai Y.X.Qiao L.Y.Sheng School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang110159China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiangChina Peking University Shenzhen InstituteShenzhen Key Lab Human Tissue Regenerate&RepairShenzhen 518057China

In this work,the influence of rolling ratios on microstructural changes and corrosion behavior of an as-rolled Mg-8 wt.%Li alloy in0.1 mol/L Na Cl solution has been investigated.It revealed that with the rolling ratio being increased from 3 to 10,theα-Mg phases were elongated and fragmented,whilst the area fraction of exposedβ-Li phases increased.Meanwhile,the corrosion performance of the alloy decreased with the increased rolling ratios.For all the samples,their corrosion processes were quite similar and can have two stages.At the initial stage with the samples being immersed for less than 6 h,the corrosion mainly occurred inβ-Li phases.When the samples were immersed for longer than 6 h,the corrosion attack transferred toα-Mg phases and the hydrogen evolution rate was accelerated.

关键词： Mg-li alloys Wrought Microstructure Corrosion performance

Suppressing Effect of Heat Treatment on the Portevin–Le Chatelier Phenomenon of Mg–4%Li–6%Zn–1.2%Y Alloy

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Journal of Materials Science & Technology 2016年第12期32卷 1232-1238页

作者： C.Q.Li d.k.xu B.J.Wang L.Y.Sheng E.H.Han School of Materials Science and Engineering Northeastern University Shenyang 110819 China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Environmental Corrosion Center Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Shenzhen Institute Shenzhen Key Lab Human Tissue Regenerate and Repair Peking University Shenzhen 518057 China

Microstructural evolution and Portevin-Le Chatelier（PLC） phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%Y alloy before and after heat treatment have been investigated.It has been demonstrated that for the as-extruded and solid solution treated（T4） samples,the PLC phenomenon could be obviously observed on tensile stress-strain curves.Moreover,the PLC phenomenon in T4 samples was more salient than that in the as-extruded condition,suggesting that the occurrence of PLC phenomenon was closely related to the super-saturation degree of solute atoms in the matrix.Since most of solute atoms were consumed for the formation of Mg Zn precipitates（β1′ and a little of β2′） during the subsequent ageing treatment（T6）,the PLC phenomenon of T6 samples was eliminated.Meanwhile,due to the pinning effect of the formed Mg Zn precipitates on mobile dislocations,the tensile strength of T6 samples was relatively higher than those of the other two conditions.

关键词： Mg-Li alloy Heat treatment Portevin-Le Chatelier （PLC） effect Precipitates