Microstructure-and-mechanical-properties-of-multi-

Microstructureandmechanicalpropertiesofmulti-componentAlCrFeNiMoxhigh-entropyalloysYongDong,YipingLu⇑,JiaorunKong,JunjiaZhang,TingjuLiSchoolofMaterialsScienceandEngineering,DalianUniversityofTechnology,Dalian116024,ChinaarticleinfoArticlehistory:Received19January2013Receivedinrevisedform27March2013Accepted27March2013Availableonline10April2013Keywords:AlloydesignMicrostructureMechanicalpropertyCrystallographyCrystalgrowthabstractTheAlCrFeNiMox(x=0,0.2,0.5,0.8,1.0)highentropyalloyswereproducedbyvacuumarcmelting,andtheirmicrostructureandmechanicalpropertieswereinvestigated.AlCrFeNi,AlCrFeNiMo0.2,andAlCrFeN-iMo0.5alloyscontainedtwobodycenteredcubic(BCC)phaseswhichwereAlNi-typeintermetalliccom-poundandFeCr-typesolidsolution.ThediffractionpeaksofthetwoBCCphasesseparatedwiththeincreaseofMocontentwhileMoelementpreferredtodissolveintoFeCr-typesolidsolution.Whenthevalueofxwashigherthan0.5,theFeCrMo-typerphaseappearedandreplacedtheFeCr-typesolidsolu-tion.TheAlCrFeNiMo0.2hadthehighestfracturestrengthof3222MPaandplasticstrainof0.287.ThehardnessincreasedobviouslyfromHV472.4toHV911.5withtheadditionofMoelement.Thesolid-solu-tionstrengtheningoftheBCCmatrixandtherphasehardeningwerethetwomainfactorsthatstrength-enedthealloys.TheAlCrFeNiMo0.2highentropyalloypossessestheexcellentmechanicalpropertieswhichimplyitspotentialapplicationinindustrialareas.2013ElsevierB.V.Allrightsreserved.1.IntroductionConventionalalloysincludeonlyoneprincipalelementandtheirperformanceisimprovedwithminoradditionsofotherele-ments,suchasiron,aluminum,magnesium,andcopper.Inordertobreakthebottleneckstageoftraditionalalloysdesignconcept,anewalloysystemcalledhighentropyalloys(HEAs)hasbeenpro-posedbyYehetal.forthefirsttime[1,2].HEAsgenerallyincludeatleastfiveprincipalelementswiththeconcentrationsofeachele-mentbeingbetween5and35at.%[2,3].Later,Zhangetal.pro-posedthesolidsolutionformationrules[4–6]andperfectedthetheoryofHEAs.ThepreviousstudieshaveshownthatHEAsonlyformthesimplefacecentercubic(FCC),bodycentercubic(BCC)orFCC+BCCsolidsolutionstructuresinsteadoflotsofintermetal-lics,whichcanbeexplainedusingthehighmixingentropytheory[7–10].Besides,HEAsareadvantageousinsomeexcellentproper-ties,suchashighhardness[11,12],highelevated-temperaturestrength[13,14],highcorrosionresistance[15,16],highwearresis-tance[17,18]andsoon.TheseadvantagesimplythatHEAshaveawidepotentialapplicationinwear-resistancetools,molds,furnaceandstructuralcomponents.AmongthepreviousHEAsinvestigated,Al–Co–Cr–Cu–Fe–Nial-loysystemhasanoutstandingmechanicalperformance[2,4].However,theelementCuwhichiseasilysegregatedintheinter-dendriticswilldeteriorateitsmechanicalproperties.Therefore,theresearchfocusedontheAl–Co–Cr–Fe–Nialloysysteminstead.ThenthemicrostructureandpropertiesofAlCoCrFeNiMox[19],AlCoCrFeNiTix[10],AlCoCrFeNiCx[20],andAlCoCrFeNiSix[21]al-loysbegintoreportoneafteranother.Inthispaper,elementCuandCoelementsareremovedandtheAlCrFeNialloyisselectedasthematrixalloy.InaccordancewiththeHEAsdesignconcept,MoelementisaddedtotheAlCrFeNialloyandthevariationofitsmicrostructureandpropertiesareinvestigated.2.ExperimentalThepurityofeachrawmaterialsusedinthisstudyisshowninTable1.TheAlCrFeNiMox(whenx=0,0.2,0.5,0.8,1.0,thealloysweredenotedasMo00,Mo02,Mo05,Mo08andMo10,respectively)alloyswerepreparedbyarcmeltingmixtureofpuremetalsinaTi-getteredhighpurityargonatmosphere.Afterthevac-uumpressurereachedto4103Pa,meltingandcastingwereperformedwiththepressureof0.01atmbybackfilledtoargon(Ar).Thealloyswererepeatedlymeltedwithelectromagneticstirringatleastfivetimesforhomogeneity.Thenthealloysweredirectlysolidifiedinawater-cooledcopperhearthandthesolidifiedingotswereabout30mmindiameterand15mminthickness(approximately70g).Thesampleswerethenpolishedandetchedindilutedaquaregiabeforeexaminingmicrostructurebyascanningelectronmicroscope(SEM,Zeisssupra55)operatedatsecondaryelectronmodeandwithanacceleratingvoltageof15kV.Chemicalcom-positionsofdifferentphaseswereanalyzedbySEMenergydispersivespectrometry(EDS),andthecrystalstructureofas-castsampleswascharacterizedbyanX-raydiffractometer(XRD,EMPYREANwithCuradiationtarget)withthe2hscanrangingfrom20to100ataspeedof4/min.Forthecompressivetest,specimenswithadiameterof5mmandalengthof10mmwerepreparedfromthemasteringotbyelectro-sparkwire-electrodecuttingandthetestwascarriedoutataspeedof3mm/min.ThehardnessmeasurementwasconductedusingaVickershardnesstester(MH-6L)underaloadof1000gfor15s.Fivemeasurementsweremadeoneachsampletoobtaintheaveragedexperimentaldate.0925-8388/$-seefrontmatter2013ElsevierB.V.Allrightsreserved.⇑Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](Y.P.Lu).JournalofAlloysandCompounds573(2013)96–101ContentslistsavailableatSciVerseScienceDirectJournalofAlloysandCompoundsjournalhomepage: