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1、MetallographicEtchingofAluminumandItsAlloysGeorgeF.VanderVoortBuehlerLtd.LakeBluff,IllinoisUSAAndElenaP.ManilovaPolzunovInstituteSt.Petersburg,RussiaPreparationofAluminumSpecimens•Grindwith240-gritSiCwater-cooledpaper,240rpm,5lbs.(20N)perspecimen,untilco-planar•Polishwith9-µmDiam
2、ondonanUltra-Pol(silk)cloth,150rpm,5lbs/specimen,5minutes(contrarotation)•Polishwith3-µmDiamondonaTridentcloth,150rpm,5lbs/specimen,4minutes(contrarotation)•Polishwith1-µmDiamondonaTridentcloth,150rpm,5lbs/specimen,3minutes(contrarotation)•Polishwith0.05-µmColloidalSilicaonaMicro
3、clothpad,120rpm,5lbs/specimen,3minutes(contrarotation)(Contra:Headandplatenrotateinoppositedirections)Standard“Black&White”EtchantsforAluminum•Keller’sReagent95mLwater,2.5mLHNO,31.5mLHCl,1.0mLHF–Immerse•CausticSodiumFluorideEtch93mLwater,2gNaOH,5gNaF•Graff-SargentEtch84mLwater,15
4、.5mLHNO,30.5mLHF,3gCrO3AnodizingwithBarker’sReagent1.8%Fluoboricacidinwater20-45Vdc,forupto2minutesExaminewithcrossedpolarizedlight,plusasensitivetint(firstorderredplate,orλplate)toseethemicrostructureincolor.Itisgoodforgrainsize,butdoesnotrevealalloysegregation.ExamplesofAnodizi
5、ngwithBarker’sReagentItdoesnotrevealalloysegregationincastalloysbutdoesdisplaythedendriteswell.ItiswidelyapplicableforrevealinggrainstructureinwroughtalloysBut,youmusthaveaconductivepath.BrightFieldPolarizedLightPL+SensitiveTint100µm100µmGrainstructureofwrought1100gradefoilaftere
6、lectrolyticpolishingandanodizingwithBarker’sreagent(20Vdc,2min),andviewedwithbrightfield(top),polarizedlight(left)andwithpolarizedlightplusasensitivetintfilter(right).NotethatcolorisnotobservedinbrightfieldbecauseaninterferencefilmisnotformedusingBarker’sreagent.As-cast(concast)1
7、100Al(>99%Al)anodizedwithBarker’sreagent(30Vdc,2min.)revealedadendriticsolidificationstructure.Notethatnoevidenceofsegregationisapparent.Originalat50X.Viewedwithcrossedpolars+sensitivetint.Wrought2024-Faluminum(Al–4.4%Cu–1.5%Mg–0.6%Mn)bar(28.5mmdiam.)showingthegrainstructureandin
8、termetallics.Magnificationbaris200µmlong