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1、NanoStructuredMaterials,Vol.11,No.8,pp.1195±1204,1999ElsevierScienceLtdPergamonCopyright©2000ActaMetallurgicaInc.PrintedintheUSA.Allrightsreserved.0965-9773/99/$±seefrontmatterPIIS0965-9773(99)00410-9COMPARISONOFGRAINSIZEDISTRIBUTIONSOBTAINEDBYXRDANDTEMIN
2、MILLEDFCCPOWDERSJ.Guerrero-PazandD.Jaramillo-ViguerasDepartmentofMetallurgicalEngineering,ESIQIE-IPN,D.F.,Lindavista,MeÂxico,CP07300(ReceivedSeptember3,1999)(AcceptedNovember21,1999)AbstractÐMeasurementsofgrainsizeinpowdersoftheCu-15at%Al,Cu-20at%Ni,Cuand
3、Nisystems,milledfordifferenttimeswereconducted.X-raydiffraction(XRD)(Warren-Averbachmethod)andtransmissionelectronmicroscopywereusedforthatpurpose.Frombothtechniques,distributionsofgraindiameter(length)wereobtained,whichpermittedtocomparebothresults.Suchr
4、esultswereinterpretedbyconsideringpreviousstudiesofparticlesizeevolutionandmicrostructuralevolution.Abettercomprehensionofphenomenathatoccurinthemechanicalalloying,asthegrainrefinementandthesolidsolutionformation,isattained.Thegrainsizeresultsobtainedbyth
5、etwotechniqueswerecoincidentfortheCu-15at%Alsystem.Thissystemdidnotpresentadherenceofthepowderstothemillingmedia.InthecaseoftheCu-20at%Ni,CuandNisystems,thatpresentedadherence,theresultswerecoincidentsolelyinthepowdermilledfor864ks.Thisisexplainedduetothe
6、microstructuralhomogenization,reacheduntilthattime.ThegrainsizeasafunctionofthemillingtimeofthetwoclassesofFCCsystems,beingreferredtotheadherencephenomenon,presentedopposedtrends.Forexample,fortheCu-at15at%Alsystem,the70%ofthepopulationofgrainshadagrainsi
7、zesmallerthan7.5,12and20nmforthemillingtimesof180,360and864ksrespectively.InthecaseoftheCu-20at%Ni,CuandNisystems,the70%ofthepopulationofgrainshadagrainsizesmallerthan35,22and16nmforthemillingtimesof180,360and864ksrespectively.Thesecontrarytrendsreflectdi
8、fferentmechanismsofgrainsizerefinement.Amaximumvalueofgrainsizeof20nmrequiredtoformthesolidsolutionintheCu-at15%AlandCu-20%atNisystemswasfound.©2000ActaMetallurgicaInc.1.IntroductionMechanismsofgrainsizerefinementfo
