镁合金彩色金相研究

重庆大学硕士学位论文镁合金彩色金相研究姓名：付启涛申请学位级别：硕士专业：材料科学与工程指导教师：潘复生2010-05I11ml150ml50mlAZ31ZK60AZ9126g2ml100ml0.5ml1ml2~4minAZZK6033g20ml50ml20ml5%~15%-AZ2/II180ºIIIABSTRACTColormetallographyisanadvancedopticaltechniquewhicharoseinthelatedevelopmentstageofmetallography.Itinvolvesmanyotherdisciplines,suchasoptics,chemistry,andcolorscience,makingthefullestuseofthepropertiesoflighttodistinguishdifferentphasesandstructuresofmaterials.Ithasmanyadvantagescomparedtocommonblack-whitemetallography.Generally,colormetallographyhasamuchhigherabilitytodisplaygrainstructure,dendritestructure,secondphases,andcompositionsegregation,providingscientistswithmoreaccurateandusefulinformationregardingthemicrostructureofmaterials.Thistechniquehasbeenappliedsuccessfullyonsteelandaluminumalloys.However,itsapplicationonmagnesiumalloysisstillinitsearlystages.Researchintotheapplicationofcolormetallographyformagnesiumalloysissignificantforthemeticulousstudyofitsmicrostructureanddevelopment.Inthepresentwork,thespecimenpreparation,formingoffilms,andobservationsofstaplemagnesiumalloyswerediscussed.Theaffectsofsurfacequalityobtainedfromdifferentpreparingmethodsoncolormetallographywerealsoexamined.Chemicaletchingwasresearched,includingtheeffectsofdifferentformulationsoverdifferentperiodsoftimeontheformationofcolormetallography.TheIonsputteringofaurumwastestedonspecimensinordertoobtaincolorcontrast.Theeffectsoftheparametersoftheinstrumentsonthecolormetallographywerealsostudied.Theresultsshowthatoptimalcolorcontrastcanbeachievedthroughtheprocessofmechanicalpolishing,sinceithasthesmallestchemicaleffectonthespecimen.However,themainproblemwithmechanicalpolishingisthatthemarkingishardtoremove.Fortunately,chemicalpolishingisusefultoremovethescarredanddeformedlayer.Itworkswellonmagnesiumalloyswithlowalloycontent,butitattacksthesurfaceofspecimenswithhighalloycontent,whichultimatelyaffectsthefinalcolorcontrastsignificantly.Electrolyticpolishingisnotsuitableforthespecimenpreparationofmagnesiumalloysunderpresentexperimentalconditions,althoughitcuresthescarification.Itleadstoeitherablackandpittedsurfaceorawhitishandgriddingsurface,bothofwhichfailtomeetthesurfacequalityrequirementsofcolormetallography.Consideringtheregents,reagent#1didnotworkonas-castorhomogenizedmagnesiumIValloyswithlowaluminumcontent,suchasAZ31oras-castZK60.However,reagent#1isusefulforrevealingcolorgraincontrastandthedendriticcrystalsofas-castAZ91(whichhasahighercontentofaluminum).Reagent#2workswellonallAZseriesofmagnesiumalloys,yetithaslittleeffectonas-castZK60.Reagent#3severelyetchedthespecimensandreturnednouseableresults.TheresultsofusingAceticpicralwith5-10%aceticacidcontentweresimilartoreagent#2,workingwellonAZseriesmagnesiumalloys.Onlylimitedsecondphasesinformationwasobtained,andnocolormetallographywasachievedbyotherreagentsincludingwaterand/oralcoholsolutionsofothercarboxylicacid,glycol,inorganicacid,chromicsalt,pyrosulfite,ammoniumsaltandpotassiumpermanganate.Anenhancedyetlimitedsecondphasesfigurecanbeobtainedbyionsputteringaurum.Ithasonlyalimitedaffect,andisveryexpensivecomparedtochemicaldeposition.Therefore,itisnotfitforuniversalapplication.Also,nousefulcolormetallographywasobtainedviatheprocessofheattinting.Manyparametersofthemicroscopeandphotographysystemhadasignificanteffectonthefinalcolorcontrast.Xenonlampsaremuchbrighterandhaveahighercolortemperaturethanhalogenlamps.Theyhaveacontinuousspectrum,similartosunlight,whichisquitesuitableforcolormetallography.Duringthisstudy,optimalcontrastcouldonlybeachievedbycrossedpolarizedlightinmostcases.Sensitivetintfilterswereusedtoraisetheinterferencelevelsothatthecolorcontrastcouldbeenhanced.Thegraincolorcontrastvarieswithaperiodof180°whentheobjectivestagerotates.Thewhitebalanceofthecameradoesnotaffectthecontrastbetweengrains,yetitdoeschangethecolor.Acolorcontrastwhichisclosesttonaturalcolorscanbeobtainedwhenthewhitebalanceofthecameraissettosunlight.Differentialinterferencecontrastgeneratednousefulcolorcontrastinthisstudy.KeyWords:Magnesiumalloys,Colormetallography,Chemicaletching,Ionsputtering,Heattint.111.121[1-10]1.2[11,12]12[13]1.1Fig1.1Schematicdiagramofblack-whitemetallography[11]1.33ab1.2Fig1.2Waysoflightabsorption40~500nm1.3a[11]dr-nsdsnMKMd0dr--d?pnsdsnMkM?1.3b??14?1%[13]1.3cdt1t2formbirefringence[14][15]F[16]ab5c1.3Fig1.3Layersformedonmetalsurfaceab1.4Fig1.4InterferenceofpolarizedlightA1AePAoM1M2AeeAoeFt1+t21-t116A0A1AooAeeAoeoeAeeee?ß[11]I0a560~1120nm1.47[17-22][11,23,24]18[11,12]1.51.5.1[25-28][29]1.3[30]9DICDICDIC[31,32][32,33]DICDIC2~3[34-38][39-43][44]1.5.2Pepperhoff[45]G.Bartz[46]BuhlerHougardy[47,48]11080[49,50][11]Klemm[51,52]Beraha[53][54,55]1.3c[23,56][12,57-59]11[38]Lacombe[60]Schaberger[61][62,63][39-43,64-66]EBSD[67]1.6[57,58][11,12,47,68]901121949T.ErnstF.Laves[69]1947P.F.George[24]TransASMGeorge1987PtODICDIC2000E.Schaberger[61]Barker[70]AZ91HP2004ASMMetalHandbookBuehlerG.F.VanderVoort[30]“”99.98%T.V.Padfield[71]“”Mg-2.5%RE-2.11%Zn-0.64%ZrMg-4.6%Zn-0.76%ZrAZ91C.Mg-9%Al-0.25%Mn-0.7%Zn-0.0008%BeG.F.VanderVoort-2004A.Maltais[23]