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1、AbstractAbstractInthispaper,theatomic-scalecomputersimulationsonretrogressionandageing-reageingofAl-Lialloyswerefirstlyworkedout.Thecomputersimulationarebasedonthemicroscopicdifusionequationwiththediscreteformatandnonequilibriumfreeenergy,whichcanbeappliedtoallprectpttationprocess,includingato
2、micclustering,ordering,growthandcoarsening,andthecounterprocesssuchasdisorderinganddissolutionduringretrogression,andthecompositionalregionsfrommetastabletoinstable.Itcomesfromnonlinearequation,andcanbeappliedtothesystemwithhighercompositionalgradation.Furthermore,Anypriorassumptiononthenewpha
3、sestructureorthemechanismsofprecipitationandretrogressionwasunnecessary,theemergenceanddissipationofpossiblenonequilibriumphasescouldbedescribedautomaticallywithoutanydatabasetosupport,andatomicpictures,orderparameters,volumefractions,structurefunctionandcorrelationfunctionofprecipitatescouldb
4、efurtherobtainedFordiferentvolumefractions,structurefunctionandcorrelationfunctionwerebothscaledatlatestageofphaseprecipitation,butthepeakandshapeofscalingstructurefunctionprofileswerediferent,themaximumvalueofwhichincreasedwiththevolumefractions.Whenskippingtoinstableregions,thevariationsofst
5、ructurefunctionprofileswithtimewerethesame:thepeakofstructurefunctionwasdecreasedandthelocationofthepeakofthestructurefunctionshiftedtowardssmallerreducedwavevectorsInthecourseofretrogression,theevolutionsofS'phasewereintheorder:stoicheometricS'phase-nonstoicheometricorderedphase--disorderedma
6、trix,includingthedifusionofsoluteatomsandthedisorderingoforderedphases.Thesolute-richregionswereformedaroundtheorderedphasesasthephasesweredissolvedduringtheretrogression,andintheend,theorderedphaseswouldbereplacedbysolute-richregionscompletely.Buttheprocessofsolute-richregionsturningintodisor
7、deredmatrixwasveryslow,anditwashardtocomebacktotheoriginalstatesduringretrogressionThemechanismsofphaseprecipitationwereverydiferentatdiferentcompositionalregionsfrommetastabletoinstable,whilethemechanismsofretrogressionwereconsistent:t