磁性的合金

*Correspondenceaddress.R.MonsBruno496ap902,Meireles-Fortaleza,60.115-190Ce,Brazil.E-mail:[e-mail]neticMaterials195(1999)107Ð111MagneticpropertiesofFeÐMoÐ5NiÐ0.05Calloyswithdi¤erentcontentsofMoF.G.AbreuHamilton*,A.BraidAdolfo,R.SilvaManuel,M.NetoJulio,R.Teodo«sioJoelMetallurgicalDepartment,COPPE,EE,FederalUniversityofRiodeJaneiro,CP68510,CEP21945-970,RiodeJaneiro,BrazilReceived19May1998;receivedinrevisedform19October1998AbstractMagneticpropertiessuchascoerciveforceH#,remanentinductionB3,squarenessB3/B4andmaximumenergyproductBH.!9foralloyswithFeÐ5NiÐ0.05Cand11,15and19wt%ofMoweredeterminedforsamplescoldrolled60,80%,90and97%followedbymagneticagingat610¡Cfor1h.Theresultsshowthattheadditionofcarbontoalloyswith11and15wt%ofMoimprovescoerciveforceH#andtheamountofMohasasigniÞcantroleonremanentinductionB3andsquarenessB3/B4.After97%ofcoldrollingandmagneticaging,analloywith11wt%ofMoreachesH#290Oe,B317800G,B3/B40.94andBH.!93.4MGOe.ValuesobtainedforH#,B3/B4andBH.!9arehigherthanthoseobtainedbyJimetal.[J.Appl.Phys.52(3)(1981)2503]inanalloywith20%ofMowithoutcarbon.(1999ElsevierScienceB.V.Allrightsreserved.Keywords:Magneticmaterials;Cobaltfreemagnets;Molybdenuminmagnets1.IntroductionFeÐMoÐNialloyswithoutcarbonshowhighmechanicalplasticityandmagneticpropertiessim-ilartoVicalloy-I,alsoknownasKoerzitTwithcomposition50wt%Co,3wt%to14wt%VandFe,whosemainapplicationsaresmallmotormag-netsandspecialpurposerecordingtapes.Theiradvantagesincludetheabsenceoftheexpensiveelementcobaltandhighmechanicalductility.Jimetal.[1]investigatedmagneticpropertiesofFeÐMoÐ5NiwithamountsofMofrom11to20%(wt%)butwithoutcarbon.Theyconcludedthatthebestmagneticpropertiesareobtainedinalloyswith20%Mo,solutionannealedbeforemagneticaging.Alloyswith15and11wt%ofMoshowedverypoorcoerciveforce(H#+90Oe)andhighre-manentinduction(B317800G).ThepresenceofMocausesprecipitationofk-Fe2Mothatisrespon-sibleformagnetichardeninginthesealloys[2].Theadditionof0.12wt%ofcarbonwasstudiedbyTavaresetal.[3]inanalloywith20wt%ofMo.Themaingoalofthisstudywastoproduceacheaperalloymeltingsteelinsteadofpureiron.Theyconcludedthatcarbonimprovedmagnetic0304-8853/99/$Ðseefrontmatter(1999ElsevierScienceB.V.Allrightsreserved.PII:S0304-8853(98)00537-XFig.1.VariationofH#with%ofreductionforalloysB,HandM.Table1ChemicalcompositionofinvestigatedalloysAlloyCNiMoCoFeB0.0525.011.0(0.01bal.H0.0504.714.5(0.01bal.M0.0575.019.3(0.01bal.propertiesH#(coerciveforce)andB3(remanence)butthealloybecamebrittle.ThepresenceofcarbonformscarbidesM6CwhereMcanbeFeorMothatbehavessimilartok-Fe2Moincreasingmagnetichardening[4].Magatetal.[5]andLujinskaiaetal.[6]showedthatseverecolddeformationpriortomagneticagingimprovedmagneticpropertiesB3andH#inFeÐ20MoÐ5Ni(wt%)alloysprobablyduetothedevelopmentoftextureandmagneticanisotropy.Inapreviouswork,Abreuetal.[7]coldrolledFeÐ20MoÐ5Niwithcarboncontentsvaryingfrom0.020wt%to0.092wt%until97%ofreductionandshowedthatcoldrollinginexcessof80%introducesmagneticanisotropyinthesealloys.TheirresultsshowedthatthereisasharpM100NS110Ttexturecomponentaftermagnetichardeningthatincreaseswithcoldrollingreduc-tion.Thisworkanalyzeshow0.05%ofcarbonin-ßuencesthemagneticpropertiesinalloyswith11and15wt%MoandhowMoinßuencesmagneticpropertiesandmagneticanisotropyofFeÐMoÐ5NiÐ0.05Cwt%alloysaftercoldrollingandmag-neticagingat610¡Cfor1h.2.MaterialsandmethodsFeÐMoÐNiingotswerepreparedbyinductionmeltingundervacuum.CompositionofeachingotisinTable1.Ingotsweresoakedat1250¡Cfor30minandthenhotrolledwith60%ofreductioninonepass.Thestripswerereheatedto1220¡Candthenwerequenchedinwater.Hot-rolledstripswerecoldworkedtogetsamples60,80,90and97%reduced.Magneticagingwasperformedat610¡Cfor1h.Magneticproperties(hysteresisloops)weremea-suredinavibratingsamplemagnetometerEGGÐPARmodel4500.ErrorforH#andB3measuredbythisequipmentarebetterthan0.1%.3.ResultsanddiscussionFig.1showsthevariationofcoerciveforceH#withpercentageofcoldrollingreductionforthe108F.G.AbreuHamiltonetal./JournalofMagnetismandMagneticMaterials195(1999)107Ð111Fig.2.VariationofB3with%ofreductionforalloysB,HandM.Table2Magneticpropertiesforsamplesolutionsannealedbeforeaging(S)andagedaftercoldrolling(D)H#(Oe)B3(G)B3/B4BH.!9(MGOe)S40886000.661.52D359120000.852.48threealloysanalyzed.CoerciveforceH#ishigherforthealloywithmoreMoandisnotsensitivetocoldrollingreduction.Molybdenumisusedinbothinquenchhardeningandprecipitationhardeningtypesofpermanentmagnets.Magneticpropertiesresultfromprecipitationhardening.MoreMoinalloycompositionresultsinmoreprecipitation.Theinßuenceofcoldrollingandconsequentlycrys-tallographicorientationoncoerciveforceH#isnotverywelldeÞnedforthisfamilyofalloys.Theorydoesactuallysuggestthattheinßuenceoforienta-tiononcoerciveforcemaydi¤erforvarioustypesofdomainprocesses[8].SomealloysincreaseH#withcrystallographicorientationlikeAlnicoandotherslikesomeferritesdecreaseH#whentheyarewellaligned.ComparingthevaluesofH#ob-tainedforalloyswithcarbonintheircompositionwiththevaluesobtainedbyJimetal.[1]forco-erciveforce,itispossibletorealizehowcarboninßuences