大部分玻璃Fe-Cr-Mo-C-B合金

BulkglassyFe–Cr–Mo–C–BalloyswithhighcorrosionresistanceS.J.Pang*,T.Zhang,K.Asami,A.InoueInstituteforMaterialsResearch,TohokuUniversity,2-1-1Katahira,Aoba-ku,Sendai980-8577,JapanReceived20July2001;accepted13December2001AbstractThepreparationofbulkglassyalloyswithhighglass-formingabilityandhighcorrosionresistanceinFe-basedsystemwassucceededbymeansofcopper-moldcasting.Thetemper-atureintervalofsupercooledliquidregion(DTx)isaslargeas53–62Kandthereducedglasstransitiontemperature(Tg=Tm)isashighas0.62–0.63forthecastFe50
xCr16Mo16C18Bx(x¼4,6,8at.%)glassyalloys.ThecorrosionratesoftheFe50
xCr16Mo16C18Bxglassyalloyswithadiameterof1.2mmwereintherangeof10
3–10
2mmyear
1in1,6and12NHClsolutionsat298K.Thebulkglassyalloysarespontaneouslypassivatedin1and6NHClsolutionswithwidepassiveregionandlowpassivecurrentdensity.Theydonotsufferpittingcorro-sionevenwhenpolarizedanodiclyin12NHClsolutionupto1.0V(Ag/AgCl).Thehighcorrosionresistanceisduetotheformationofchromium-richpassivefilmsduringimmersioninHClsolutions.Inaddition,theincreaseofboroncontentinalloysimprovesthecorrosionresistanceofthebulkglassyalloyswithinthecompositionrangeexamined.
2002ElsevierScienceLtd.Allrightsreserved.Keywords:Bulkmetallicglass;Iron-basedalloy;Copper-moldcasting;Glass-formingability;Spontaneouspassivation1.IntroductionForthelastthreedecades,avarietyofcorrosionresistantamorphousalloyshavebeenprepared[1–5].However,theyexhibitlowglass-formingability(GFA)andhavebeenmainlyfabricatedasmelt-spunribbonsandsputteredthinfilms.(2002)1847–1856*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](S.J.Pang).0010-938X/02/$-seefrontmatter
2002ElsevierScienceLtd.Allrightsreserved.PII:S0010-938X(02)00002-1Thelimitationsofsizeandshapeaswellaslowthermalstabilityhavepreventedafurtherextensionoftheirapplicationfields.SincethesynthesisofbulkglassyalloysinMg-[6],Ln-[7]andZr-[8,9]basedsystemswhichhavealargesupercooledliquidregionbeforecrystallizationandhighresistanceagainstcrystallization,theglassyalloyshaveattractedmuchattentionasnewmaterialsinscienceandengineeringfields[10].Subsequently,theiralloysystemshavebeensignificantlyextendedforthelastfiveyears,suchastoFe-,Co-andNi-basedsystems[10–14].However,node-taileddataconcerningcorrosionresistanceofthebulkglassyalloysinaggressivemediahavebeenreported.Asisknown,Zr-basedbulkglassyalloysarenotcor-rosionresistantinaggressiveHClsolutions,althoughtheyexhibitgoodcorrosionresistanceinH2SO4andNaClsolutions[15].Itisthereforeessentialtodevelopnewcorrosionresistantbulkglassyalloysfortheapplicationofglassyalloystoengi-neeringfieldswithaggressiveenvironments,suchaschemicalapplications.ThefirstFe-basedbulkglassyalloyswerepreparedinFe–(Al,Ga)–(P,C,B)andFe–M–(Al,Ga)–(P,C,B)(M¼Cr,Mo,Nb)systemsin1995[11],andfollowedbyFe–(Zr,Nb)–B[10]andFe–Ga–(P,C,B)[16]systems.AlltheseglassyalloyshaveahighGFAwhichisamainrequisitefortheformationofbulkglassyalloys.However,theircorrosionresistancewasnotconfirmed.ForFe-basedbulkglassyalloys,highme-chanicalstrength,softmagneticpropertiesandhighcorrosionresistanceareex-pected.Consequently,itisimportanttosearchfornewFe-basedbulkglassyalloyscorrosionresistantinaggressivemedia.Inapreviouswork[17]thepresentauthorshavefoundthatmelt-spunFe–Cr–Mo–C–BalloyshaveahighGFAandgoodcorrosionresistanceinaggressiveHClsolutions.Thepresentpaperaimstoclarifytheglass-formationcompositionrangeandcorrosionbehaviorofbulkglassyFe50
xCr16Mo16C18Bxalloyspreparedbyacopper-moldcastingtechnique.2.ExperimentalproceduresThealloyswithnominalcompositionsofFe50
xCr16Mo16C18Bx(x¼3,4,6,8,10at.%)wereinvestigated.TheingotswerepreparedfromamixtureofpureFe,Cr,Mo,CandBbyhighfrequencyinductionmeltinginanargonatmosphere.Fromtheingots,bulkalloysamplesinarodformwithadiameterof1.2mmwerepreparedbyacopper-moldcastingmethod.Thestructureofspecimensthuspreparedwasex-aminedbyX-raydiffraction.Thethermalstabilityassociatedwithglasstransition,supercooledliquidandcrystallizationwasinvestigatedbydifferentialscanningcal-orimetry(DSC)ataheatingrateof0.67Ks
1.Themeltingtemperature(Tm)wasmeasuredbydifferentialthermalanalysis.Corrosionbehavioroftheglassyalloyswasevaluatedbyweightlossandelect-rochemicalmeasurements.Priortoimmersiontestandelectrochemicalmeasure-ments,thespecimensweredegreasedinacetone,washedindistilledwateranddriedinair.Electrolytesusedwere1,6and12NHClsolutions,whichwerepreparedfromreagentgradechemicalanddistilledwater.ThecorrosionrateswereestimatedfromtheweightlossafterimmersioninHClsolutionsopentoairat298Kforoneweek.1848S.J.Pangetal./CorrosionScience44(2002)1847–1856Aftertheimmersiontest,thespecimenswerewashedindistilledwater,dried,andsubjectedtoweightlossmeasurementandobservationbyscanningelectronmicro-scope(SEM).Electrochemicalmeasurementswereconductedinathree-electrodecellusingaplatinumcounterelectrodeandaAg/AgClreferenceelectrode.Potentiody-namicpolarizationcurvesweremeasuredwithapotentialsweeprateof50mVmin
1inHClsolutionsopentoairat298Kafterimmersingthespecimensfor20min,whentheopen-ci