Effect-of-Nb-addition-on-the-magnetic-properties-a

EffectofNbadditiononthemagneticpropertiesandmicrostructureofFePCCunanocrystallinealloyR.Xiang1•S.X.Zhou1•B.S.Dong1•Y.G.Wang2Received:23January2015/Accepted:13March2015/Publishedonline:20March2015SpringerScience+BusinessMediaNewYork2015AbstractTheeffectsofNbadditiononthemicrostruc-ture,crystallisationbehavior,andsoftmagneticpropertiesofFe83.25-xP9C7Cu0.75Nbx(x=0,0.5,1,2,3)alloyswereinvestigated.TheexperimentalresultsdemonstratethatproperNbadditionimprovestheglass-formingabilityandenhancesthesoftmagneticpropertiesofthisalloysystem.TheFe82.75P9C7Cu0.75Nb0.5alloyannealedat573–773Kfor10min,inwhicha-Fenanocrystallinephasewithdi-ameterof5–20nmprecipitatedfromtheamorphousma-trix,whilealloyannealedat743Kshowsthebestsoftmagneticproperties.TheresultingFe82.75P9C7Cu0.75Nb0.5nanocrystallinealloyexhibitedahighsaturationmagneticfluxdensity,Bs,of1.66T;alowcoercivity,Hc,of6.8A/m;andahigheffectivepermeability,le,of29,000at1kHz.ThesecharacteristicsaresuperiortocorrespondingpropertiesofFePCalloys.Theseresultsindicatethatthisalloyisapromisingsoftmagneticmaterial.1IntroductionFe-basednanocrystallinesoftmagneticalloysproducedbycrystallizingamorphousprecursorshavebeenwidelyin-vestigatedbothexperimentally[1–3]andtheoretically[4–6]fromviewpointofphysics,materialsscience[7–9],andengineeringapplicationsbecauseoftheirexcellentsoftmagneticproperties[10–12].Finemet[13],Nanoperm[8,14],Hitperm[15]andtheirderivatives,arethetypicalrep-resentativesandwidelyusedforvariousactualapplicationssuchastransformers,motors,inductors,etc.However,onehasbeenshowntoimprovethemagneticpropertiesofex-istingalloysandseekingalternativealloyswithbetterpropertiesand/orlowproductioncosts[16,17].Forexample,aseriesofnewFe-basednanocrystallinealloyswiththehighmagneticfluxdensityBs,basedonthesystemofFe–Si–B–P–Cu,havearousedgreatinterestinbothacademicandin-dustrialfields[3,18,19].WehavesuccessfullyfabricatedanewkindofnanocrystallinesoftmagneticalloyFe83.25P9-C7Cu0.75[20].Theexcellentsoftmagneticpropertiesac-companiedbysimplealloycomposition,lowmaterialcostandenergy-savingannealingprocessmakethisalloyapromisingcandidateforfutureindustryuse.Althoughthisalloyhasshownmanymerits,therealsoexistsomeshort-comingsthatneedtobeovercome.Forexample,theshortannealingtimemakestheFe83.25P9C7Cu0.75alloyhardlyusedinindustrialproductionandtheoptimalannealingtemperaturerangeofthisalloyislowandnarrow,whichleadstohighdemandsforhightemperatureandlargetem-peraturerangeintheannealingprocess.ItiswellknownthatthesubstitutionofFetoadditionalelementsinFinemetal-loys,suchasCo,AlorCr,couldextendtheiroutstandingsoftmagneticpropertiestoelevatedtemperatures[21].However,theCoadditiondeterioratesthesoftmagneticproperties.Increasingthevolumefractionofthecrystallinephasewithcoarseningthea-Fegrainsduringthecrystallizationan-nealingprocesswilllowerthesaturationmagneticfluxdensityBsofthenanocrystallinealloy[22].ProperamountofNbhaseffectininhibitingthegraingrowth,whileNbhaslessinfluencethanCoondecreasingBs[8,23].Meanwhile,NbhasnegativeenthalpiesofmixingwithelementinFePCCualloy[24,25],whichmaybebeneficialtoimprovingtheglass-formingabilityofthepresentalloy[10].Therefore,we&[e-mail];[e-mail]1AdvancedTechnology&MaterialsCo.,Ltd.,ChinaIron&SteelResearchInstituteGroup,Beijing100081,China2InstituteofPhysics,ChineseAcademyofSciences,POBox603,Beijing100080,China123JMaterSci:MaterElectron(2015)26:4091–4096DOI10.1007/s10854-015-2950-2decidedtopartiallysubstituteNbforFeandprepareFe83.25-xP9C7Cu0.75Nbx(x=0.5,1,2,3)alloys,inthehopesthatdoingsowouldenhancethemagneticsoftnessatelevatedtemperatures.TheeffectsofNbadditiononthemicrostructure,crystallizationbehavior,andsoftmagneticpropertiesoftheamorphousandnanocrystallinephasesturnedouttobequiteinteresting.Thispaperdescribesourinvestigationofthesoftmag-neticproperties-includingthesaturationmagneticfluxdensity,coercivity,andpermeability—oftheFePCCuNbnanocrystallinealloysystemwithNbcontentintherangeofx=0.5tox=3.Additionally,wedescribethegrainsizeofthenano-scalecrystallinephasesandthecrystal-lizationbehaviorofthevaryingannealingtemperature.OurresultsleftuswiththeconclusionthatthenanocrystallinealloywithNbcontentofx=0.5exhibitedahighsatura-tionmagnetisationof1.66T,lowcoercivityof6.8A/m,andhighpermeabilityof2.99104at1kHz.2ExperimentalprocedureWeusedarcmeltingmixturesconsistingofFe(99.99%bymass),Nb(99.99%bymass),Cu(99.99%bymass),premeltedFe–C(99.9%bymass),andFe3P(99.9%bymass)inahighlypurifiedAratmospheretoprepareFePCCuNballoyingots.Viasingle-rollermeltspinning,weproducedamorphousFe83.25-xP9C7Cu0.75Nbx(x=0.5,1,2,3)alloyribbons[26].Theribbonswereapproximately1.5mmwideand20lmthick.Weobtainednanocrys-tallinealloyscomposedofananocrystallinephaseem-beddedintheamorphousmatrixasaresultofthecrystallizationoftheas-quenchedamorphousunderproperannealingconditions.Themicrostructuresofas-quenchedandannealedsampleswereidentifiedbyX-raydiffraction(XRD)withCu-Karadiationandtransmissionelectronicmicroscopy(TEM),respectively.Weevaluatedthemeangrainsize,D,ofthea-FephasebyusingtheSche