简介:Samplesofacobalt-basedalloythatunderwentasurfacetreatmentwereevaluated.Thesamples,whichwereobtainedbycastingalloyASTMF75,weregroundandpolishedononesideuntilamirrorfinishwasobtained.Thesampleswereencapsulatedinwollastonite(W)usinguniaxialpressure,treatedat1220℃for1handsubsequentlytemperedinwater.Thecharacterisationofthesampleindicatedthatpartoftheceramicencapsulatingmaterialwasmechanicallyincorporatedonthemetallicsurfacebygrowthoftheoxidelayerofthealloy.Afterthermaltreatment,aseriesofspecimensweresubmergedinasolutionwith5-foldsimulatedbodyfluid(5SBF)for3,5and21days.Characterisationbyscanningelectronmicroscopy(SEM),energydispersivespectroscopy(EDS)andX-raydiffraction(XRD)indicatednucleationandgrowthofahomogenouslayerofapatite,beginningonthethirddaywhenthesamplewassubmerged.
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简介:TheatomicscalecomputersimulationforinitialprecipitationmechanismofNi75Al6V19alloywascarriedoutforthefirsttimebyemployingthemicroscopicdiffusionequation.Theinitialprecipitationprocesswasinvestigatedthroughsimulatingtheatomicpicturesandcalculatingtheorderparametersofthetwokindsoforderedphases.Simulationresultsshowthattheγ′orderedphaseprecipitatedearlierthanθorderedphasebycongruentordering+spinodaldecompositionmechanismandthusproducedanonstoicheometricγ′singleorderedphase.Then,thenonstoichiometricθphaseprecipitatedbyanon-classicalnucleationandgrowthmechanismattheAPBSofγ′phase.
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