会员注册 | 登录 | 微信快捷登录 支付宝快捷登录 QQ登录 微博登录 | 帮助中心 人人文库renrendoc.com美如初恋!
站内搜索 百度文库

热门搜索: 直缝焊接机 矿井提升机 循环球式转向器图纸 机器人手爪发展史 管道机器人dwg 动平衡试验台设计

外文翻译--高耐腐蚀涂层的纳米镍AZ91D镁合金 英文版.pdf外文翻译--高耐腐蚀涂层的纳米镍AZ91D镁合金 英文版.pdf -- 5 元

宽屏显示 收藏 分享

资源预览需要最新版本的Flash Player支持。
您尚未安装或版本过低,建议您

ystallineMaterials,130025,15paper.ThesurfacemorphologiesofthecoatingswerestudiedbySEM1.Introductionresistance,solderability,electricalconductivityordecorativeappearance.Thiscanbeaccomplishedbycoatingthepartswithametalthathasthedesiredpropertiesnecessaryfortheelectrolessnickelplatingandzincimmersion2.Itcanbenotedthatinmanypreviousreportsontheelectrolessplatingonmagnesiumalloys3–6,thenickelionsweretheplatingbath.SurfaceCoatingsTechnology200Magnesiumisbecomingincreasinglysignificantasalightweightmetalstructuralmaterialwithadensityof1.74g/cm3inmanyindustriesaircraftconstruction,spacetechnology,optics,andautomobilemanufacturing,forexample.However,magnesiumisintrinsicallyhighlyreactiveanditsalloysusuallyhaverelativelypoorcorrosionresistance,whichrestrictstheapplicationofmagnesiumalloysinpracticalenvironments.So,itisoftendesirabletoalterthesurfacepropertiesofamagnesiumormagnesiumalloyworkpieceinordertoimproveitscorrosionandwearspecificapplication1.Sincemagnesiumisoneofthemostelectrochemicallyactivemetals,anycoatingsonmagnesiumalloysshouldbeasuniform,adheredandporefreeaspossible.Oneofthemostcosteffectiveandsimpletechniquesforintroducingametalliccoatingtoasubstrateistheplatingtechniques,includingelectrolessplatingandelectroplating.Furthermore,magnesiumisclassifiedasadifficultsubstratetoplatemetalduetoitshighreactivity.Asforelectroplatingonthemagnesiumalloy,therearecurrentlytwoprocessesusedforplatingonmagnesiumandmagnesiumalloysdirectandFESEM.ThencNicoatinghadanaveragegrainsizeofabout40nmandanevident{200}preferredtexturerevealedbyXRD.ThehardnessofthencNicoatingwasabout580VHN,whichwasfarhigherthanthatabout100VHNoftheAZ91Dmagnesiumalloysubstrate.TheelectrochemicalmeasurementsshowedthatthencNicoatingonthemagnesiumalloyhadthelowestcorrosioncurrentdensityandmostpositivecorrosionpotentialamongthestudiedcoatingsonthemagnesiumalloy.Furthermore,thencNicoatingontheAZ91Dmagnesiumalloyexhibitedveryhighcorrosionresistanceintherapidcorrosiontestillustratedinthepaper.ThereasonsforanincreaseinthecorrosionresistanceofthencNicoatingonthemagnesiumalloyshouldbeattributabletoitsfinegrainstructureandthelowporosityinthecoating.D2005ElsevierB.V.Allrightsreserved.KeywordsNanocrystallinenickelMagnesiumalloyElectroplatingElectrolessnickelCorrosionmagnesiumalloywithdifferentthicknesswerealsopresentedintheAbstractNanocrystallinencNicoatingwasdirectcurrentelectrodepositedontheAZ91Dmagnesiumalloysubstrateaimedtoimproveitscorrosionresistanceusingadirectelectrolessplatingofnickelastheprotectivelayer.Ascomparison,twoelectrolessNicoatingsontheHighcorrosionresistancenanocrmagnesiumChangdongGu,JiansheLian,JinguoKeyLabofAutomobileMaterials,MinistryofEducation,CollegeofChangchunReceived22March2005acceptedAvailableonline02578972/seefrontmatterD2005ElsevierB.V.Allrightsreserved.doi10.1016/j.surfcoat.2005.07.001Correspondingauthor.Fax864315095876.Emailaddresslianjsjlu.edu.cnJ.Lian.NicoatingonAZ91DalloyHe,ZhonghaoJiang,QingJiangScienceandEngineering,JilinUniversity,NanlingCampus,Chinainrevisedform4July2005August200520065413–5418www.elsevier.com/locate/surfcoatprovidedbybasicnickelcarbonateinDifferentfromthemethodsmentionedabove,directelectrolessnickelplatingontheAZ91Dmagnesiumalloywasquicklyaspossiblebetweenanytwostepsofthetreatments.ThedirectelectrolessnickelplatingwiththehardnesstesterwithVickersindenter,ataloadof100ganddurationof15s.ElectrochemicalmeasurementswereperformedonanElectrochemicalAnalyzerCHI800,Shanghai,China,whichwascontrolledbyacomputerandsupportedbysoftware.LinearSweepVoltammetryexperimentswerecarriedoutina3wt.NaClaqueoussolutionusingaclassicthreeelectrodecellwithaplatinumplatePtascounterelectrodeandanAg/AgClelectrode207mVvs.SHEasreferenceelectrode.Beforetesting,theworkingelectrodewascleanedinacetoneagitatedultrasonicallyfor10min.TheexposedareafortestingwasobtainedbydoublycoatingwithepoxyresinEP651leavinganuncoveredareaofapproximately1cm2.Thereferenceandplatinumelectrodeswerefixedneartotheworkingelectrodeabout0.5mm,whichcouldminimizetheerrorsduetoIRdropintheelectrolytes.Duringthepotentiodynamicsweepexperiments,thesampleswerefirstimmersedinto3wt.NaClsolutionforabout20mintostabilizetheopencircuitpotential.Potentiodynamiccurveswererecordedbysweepingtheelectrodepotentialfromavalueofabout300–400mVlowertoavalueof500–600mVupperthanthecorrosionpotential,respectively,atasweepingrateof5mV/s.Thelogi–EcurveswereTime30minabout15µmFig.1.ThetechnicalflowchartoftheelectroplatingncNiontheAZ91Dmagnesiumalloy.Technologythicknessofabout10AmonAZ91Dmagnesiumalloy7wasusedastheprotectivelayerforfurtherplatingonthemagnesiumalloy.TheelectroplatingncNicoatingonthemagnesiumalloywasdirectcurrentelectroplatedfromabathcontainingnickelsulfate,nickelchloride,boricacidandsaccharinatapHof5.0andatemperatureof50C.Duringtheelectrodepositionprocess,theanodewasusedanelectrolyticnickelplate.TheoperationofelectroplatingncNicoatingwasundertakenforabout30minwhichwouldgivethecoatingwiththethicknessofabout15Am.AscanningelectronmicroscopeSEM,JEOLJSM5310,JapanandafieldemissionscanningelectronmicroscopeFESEM,JEOLJSM6700F,JapanwereemployedfortheobservationsofthesurfaceofthecoatingsandthecrosssectionmorphologyandanEDXattachmentwasusedforqualitativeelementalchemicalanalysis.CrystallinestructureofthesamplewasstudiedbytheXraydiffractometerXRD,RigakuD/max,JapanwithaCutargetandamonochronmatorat50kVand300mAwiththescanningrateandstepbeing4/minand0.02,recentlyundertakenbyusingaplatingbathcontainingsulfatenickel7.Intherecentyears,therehavebeenconsiderableinterestsinunderstandingthemechanicalproperties,thecorrosionresistanceandthewearresistanceofncmetalsproducedbyelectrodeposition,forexample8–14.Accordingtothem,ncmaterialsexhibitedmanyunusualmechanicalandelectrochemicalpropertiescomparedwithconventionalpolycrystallineoramorphousmaterials.Sointroducinganccoatingcombinedthehighcorrosionresistancewithgoodwearresistanceonmagnesiumalloysubstratewouldbeverypromising.Inthepresentpaper,theelectrolessNiplatingfromanacidicbath7wasfirstdepositedonAZ91Dmagnesiumalloyastheprotectivelayerforthefurtherelectroplatingoperation,andthenancnickelcoatingwasdirectcurrentelectroplatedontheprotectivelayer.ThemicrostructuresandtheelectrochemicalpropertiesofthecoatingsontheAZ91DmagnesiumalloysubstratewerestudiedbySEM,FESEM,XRDandelectrochemicalmeasurement.2.ExperimentalThesubstratematerialusedwasAZ91Ddiecastmagnesiumalloywithasizeof30C240C25mm.Thealloywasmainlycontainedabout9.1Al,0.64Zn,0.17Mn,0.001FeandMgbalance.Thesampleswereabradedwithno.1500SiCpaperbeforethepretreatmentprocesses.ThetechnicalflowchartoftheelectroplatingontheAZ91DmagnesiumalloyisshowninFig.1.ThesampleswerecleanedthoroughlywithdeionizedwaterasC.Guetal./SurfaceCoatings5414respectively.ThehardnessofthemagnesiumalloyandthecoatingswereevaluatedusingaHXD1000microAlkalinecleaningNaOH45g/lNa3PO412H2O10g/lTemperature65°CAcidpickleCrO3125g/lHNO370V/V100ml/lTime40sRoomtemperatureFluorideactivationHF40V/V350ml/lTime10sRoomtemperatureElectrolessplatingprotectivelayerref.7Time15minabout10µmElectroplatingnanocrystallineNiNiSO46H2O250300g/lNiCl26H2O3040g/lH3BO33045g/lC7H5NO3S0.10.2g/lCurrentdensity3A/dm220020065413–5418measuredandplottedaftertheaboveelectrochemicalmeasurements.ThecorrosionpotentialEcorrandcorrosioncurrentdensityicorrweredetermineddirectlyfromtheselogi–EcurvesbyTafelregionextrapolation.Acidimmersiontestin10HClsolutionatroomtemperaturewasundertakentotestthecorrosionresistanceofthencNicoatingonthemagnesiumalloy.Ifthereweremicroporesinthecoatings,thecorrosionsolutionwoulderodethemagnesiumsubstratethroughthepores.Duetothehighchemicalactivityofthemagnesium,theHinthecorrosionsolutionwouldbereducedbythemagnesiumandturnedintothehydrogengasbubbles.Sothetimeintervalbetweenthestartofthetestandthefirsthydrogengasbubblearisingfromthecoatingsurfacecouldbeusedtodonatethecorrosionresistanceofthecoatingsonthemagnesiumalloysubstrate.Forcomparison,theelectrolessplatingnickelcoatingswithdifferentthickness10and25Amwerealsotestedinthepaper.3.Resultsanddiscussions200peakviatheScherrerequation16dXRD¼kkbhðÞcoshð1ÞWherekistheXraywavelength,btheFWHMfullwidthofhalfmaximumofthe200diffractionpeak,hthediffractionangleandtheconstantkC2291.FromEq.1theaveragegrainsizeofthisncNiwasabout40nm.Inaddition,theXRDresultsalsoshowedthatthencNicoatinghadanevident{200}preferredtexture.Infact,Nielectrodepositsareknownforgivingnumerous,welldefinedpreferredorientationsdependingonelectrodepositionconditions,i.e.electrolytecomposition,temperature,pH,currentdensity,stirringandorganicadditions17,18.The{200}preferredtextureofthencNiinthisstudymaybeattributabletothegivenelectrodepositionconditionswhichmayleadtohigherelectrodeoverpotentialandreducedconcentrationofNi2attheelectrodesurface18.Fig.3ashowedthetypicalsurfacemorphologyoftheasdepositedncNicoating.ItcanbeseenthattheasdepositedsurfaceofthencNicoatingwasverycompactandnocolonystructures,whichwastotallydifferentfromthecauliflowerlikeinmicrometersizesurfacemorphologyoftheelectrolessnickeldepositionseeFig.3b.Moreover,theasdepositedsurfaceofthencNicoatingexhibitedaflatandmirrorlikeappearanceandthe25000NiC.Guetal./SurfaceCoatingsTechnology20304050607080050001000015000200002030405060708005001000150020002500a2θ/deg.20304050607080050010001500bIntensity/CPSMg17Al12MgcFig.2.TheXRDpatternsoftheelectroplatingNiontheAZ91Dmagnesiumalloyatdifferentintervals,aAZ91Dmagnesiumalloy3.1.MicrostructuresandhardnessofthecoatingsFig.2ashowedthepatternofXRDoftheAZ91Dmagnesiumalloy,whichindicatedthatthesubstratealloyconsistedofprimaryaMggrainssurroundedbyaneutecticmixtureofaandbMg17Al1215.ItalsocanbeseenfromtheXRDpatternofFig.2bandthemorphologyofFig.3thatafterelectrolessNiplatingforabout15min,theAZ91Dmagnesiumalloywasfullycoveredbytheelectrolessnickeldeposition.Thephosphoruscontentintheelectrolessdepositionwasverylow,becauseNiwasfirstdepositedonthesurfaceofmagnesiumalloyaccordingtothedepositionmechanismofelectrolessplatingonthemagnesiumalloy7.TheXRDanalysisresultsoftheasdepositedelectroplatingncNicoatingwasshowninFig.2substrate,belectrolessplatingonthesubstratefor10min,ctheelectroplatingncNicoating.c.ThegrainsizedofncNicanbedeterminedfromtheFig.3.ThesurfacemorphologyofathencNicoatingandbtheelectrolessnickelplatingontheAZ91Dmagnesiumalloyforabout10min.20020065413–54185415grainsizeofthedepositscouldnotberesolvedbyconventionalSEMobservations.Inordertomakeaclearobservationofthefinegrainstructure,specimenofthisncNiwaspolishedandcorrodedbydilutenitrate/ethanolsolutionbeforetheSEMobservation.ThesurfacemorphologyofthencNiafterabovepretreatmentswasshowninFig.4.TheveryuniformncgrainstructurescanbeseenonthesurfaceofncNiafterslightlycorroded.Fig.5ashowedthecrosssectionmorphologyofthencNicoatingontheAZ91Dmagnesiumalloy.ToindicatethesubstrateandtwotypesoftheNilayersonthecrosssectionofthecoating,thesubstrate,theprotectivelayerandthencNilayerweremarkedbythelinewithtwoarrows,respectively,intheFig.5a.Fromthisfigure,itcanbeseenthattheacidpicklepretreatmentpriortoelectrolessplatingprotectivelayerforthemagnesiumalloyprovidessurfacepitstoactassitesformechanicalinterlockingtoimproveadhesion7.Moreover,therewerenoobviousboundariesbetweentheprotectivelayerandthencNilayer,whichindicatedthatthencNilayerwastightlyattachedtotheprotectivelayer.Inaddition,thencNilayershowedverycompactandnoporesfromitscrosssectionobservation.Fig.5bgavethequalitativeelementanalysisofthencNicoatingontheAZ91DmagnesiumalloybyEDXanalysis.ForthelowerphosphorouscontentintheprotectivelayerpreviousdepositedontheAZ91Dmagnesiumalloysubstrate,thedistributionofelementofphosphorouswasnotdetectedbyEDX.FromtheelementsdistributingfromthesubstratetothecoatingsurfacealongthelinelabeledinFig.5a,itcanbeseenthatthecoatingwasconnectedcloselytothemagnesiumalloysubstrate.Fig.4.ThesurfacemorphologyoftheelectroplatedncNicoatingafterpolishingandcorrodedbydilutenitrate/ethanolsolution.C.Guetal./SurfaceCoatingsTechnology20020065413–54185416Fig.5.aThecrosssectionmorphologyoftheNicoatingontheAZ91DmagnesiummagnesiumalloybyEDXanalysis,scanningfromthesubstratetothecoatingsurfacealloy,bthequalitativeelementanalysisofcoatingontheAZ91Dalongthelinelabeledinthefigure.
编号:201311171352516389    大小:400.76KB    格式:PDF    上传时间:2013-11-17
  【编辑】
5
关 键 词:
教育专区 外文翻译 精品文档 外文翻译
温馨提示:
1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供交流平台,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
  人人文库网所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

当前资源信息

4.0
 
(2人评价)
浏览:25次
淘宝运营上传于2013-11-17

官方联系方式

客服手机:13961746681   
2:不支持迅雷下载,请使用浏览器下载   
3:不支持QQ浏览器下载,请用其他浏览器   
4:下载后的文档和图纸-无水印   
5:文档经过压缩,下载后原文更清晰   

相关资源

相关资源

相关搜索

教育专区   外文翻译   精品文档   外文翻译  
关于我们 - 网站声明 - 网站地图 - 友情链接 - 网站客服客服 - 联系我们
copyright@ 2015-2017 人人文库网网站版权所有
苏ICP备12009002号-5