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Short-time Oxidation of Alloy 690 in high-temperature and high-pressure Steam and Water

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Journal of Materials Science & Technology 2012年第6期28卷 562-568页

作者： F.huang J.Q.Wang e.h.han W.Ke State Key Laboratory for Corrosion and Protection Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280℃ for 1 h was investigated by scanning electron microscopy （SeM）, atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes （electropolished, mechanically polished, ground, and as-received） were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100-200 nm for the as-received samples, 150-250 nm for the samples ground to 400# and 10-20 nm for the samples ground to 1500#, mechanically polished, and electropolished.

关键词： Alloy 690 Oxidation high-temperature water Surface finish X-ray photoelectron spectroscopy (XPS)

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 *** 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 ***,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 ***,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 ***,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

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

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 *** alloys,considered the lightest metallic structural material among others,have great potential for applications as secondary load components in the transportation and aerospace *** fatigue evaluation of Mg alloys under elastic stress amplitudes is very important in ensuring their service safety and *** 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 ***,for Mg alloys with shrinkage porosities and inclusions,fatigue cracks will preferentially initiate at these defects,remarkably reducing the fatigue *** 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 ***,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

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 *** 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 ***,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 *** 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 ***,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

Microstructures and mechanical properties of the age hardened Mg-4.2Y-2.5Nd-1Gd-0.6Zr(We43)microalloyed with Zn

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Journal of Magnesium and Alloys 2014年第2期2卷 109-115页

作者： Y.h.Kang D.Wu R.S.Chen e.h.han State Key Laboratory for Corrosion and Protection Institute of Metal ResearchChinese Academy of Sciences62 Wencui RoadShenyang 110016China University of the Chinese Academy of Sciences Beijing 100049China

The effect of trace addition of 0.2 wt.%Zn on the microstructures and mechanical properties of the age-hardening Mg-4.2Y-2.5Nd-1Gd-0.6Zr(wt.%)(We43)alloy has been *** compared with the We43 alloy after solid solution treatment at 525 ℃,the block-like Zn-Zr phase was still observed in the We43-0.2Zn ***,the time for We43-0.2Zn alloy to get peak hardness at 250 ℃ was two hours,a half earlier than that in We43 alloy,meaning a accelerated age precipitation kinetics has been achieved due to the addition of 0.2 wt.%*** with 0.2 wt.%Zn enhanced the ultimate tensile strength(UTS)slightly and ductility significantly both in the solutionized and peak aged *** enhancement in strength and ductility is possible associated with the larger volume fraction of precipitation phases due to a reduction of the solubility of rare earth elements(Re)in theα-Mg matrix,the larger aspect ratio(length to width)of precipitates and a decrease in stacking fault energy by addition of Zn.

关键词： Magnesium alloy Microalloying Microstructures Mechanical properties

Stress corrosion cracking susceptibility of a high strength Mg-7%Gd-5%Y-1%Nd-0.5%Zr alloy

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Journal of Magnesium and Alloys 2014年第4期2卷 335-341页

作者： S.D.Wang D.K.Xu e.h.han C.Dong Laboratory of Materials Modification by Laser Electron and Ion BeamsSchool of Materials Science and EngineeringDalian University of TechnologyDalian 116024China environmental Corrosion Center Institute of Metal ResearchChinese Academy of Sciences62 Wencui RoadShenyang 110016China

Through performing the tensile tests with different strain rates in 3.5 wt.%NaCl solution,the stress corrosion cracking(SCC)behavior and the effect of strain rate on the SCC susceptibility of an extruded Mg-7%Gd-5%Y-1%Nd-0.5%Zr(eW75)alloy have been *** demonstrate that the alloy is susceptible to SCC when the strain rate is lower than 5×10^(−6) s^(−1).At the strain rate of 1×10^(−6) s^(−1),the SCC susceptibility index(I_(SCC))is 0.96 and the elongation-to-failure(ε_(f))is only 0.11%.Fractography indicates that the brittle quasi-cleavage feature is very obvious and become more pronounced with decreasing the strain *** analysis confirms that the cracking mode is predominantly transgranular,but the partial intergranular cracking at some localized area can also ***,it seems that the crack propagation path is unrelated to the existing phase particles.

关键词： Magnesium alloy Stress corrosion cracking Strain rate Pitting corrosion

Quasi-in-situ observing the rare earth texture evolution in an extruded Mg-Zn-Gd alloy with bimodal microstructure

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Journal of Magnesium and Alloys 2021年第5期9卷 1818-1827页

作者： M.G.Jiang C.Xu h.Yan T.Nakata Z.W.Chen C.S.Lao R.S.Chen S.Kamado e.h.han College of Mechatronics and Control engineering Shenzhen University3688 Nanhai AveShenzhen 518060China The Group of Magnesium Alloys and Their Applications Institute of Metal ResearchChinese Academy of Sciences62 Wencui RoadShenyang 110016China School of Materials Science and engineering Harbin Institute of TechnologyHarbin 150001China Department of Mechanical engineering Nagaoka University of TechnologyNagaoka 940-2188Japan

The static recrystallization and associated texture evolution were investigated in an extruded Mg-Zn-Gd alloy with bimodal microstructure based on a quasi-in-situ electron back-scatter diffraction(eBSD)*** typical rare earth(Re)texture formed during annealing,evolving from the bimodal microstructure with[1010]basal fiber texture that consisted of fine recrystallized(RXed)grains and coarse unrecrystallized(un RXed)grains elongated along the extrusion *** both RXed and un RXed regions,the RXed nucleation produced randomized orientations without preferred selection and the RXed grains with Re texture orientation had more intensive growth ability than those with basal fiber orientation,thereby leading to the preferred selection of Re texture orientation during grain *** relationships between stored strain energy,solute drag,grain growth and texture evolution are discussed in *** study provided direct evidence of the Re texture evolution in an extruded Mg-Re alloy,which assists in understanding the formation mechanisms for Re texture during extrusion and better developing wrought Mg alloys with improved formability.

关键词： Magnesium alloy Rare earth texture extrusion Annealing Recrystallization