脉冲电流作用下纯铝熔体凝固晶核的迁移行为.pdf

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1、Availableonlineatwww．sciencedirect．tomTransactionsof镪ScienceDirectNonferrousMetalsSocietyofChinaPressTrans．NonferrousMet．Soc．China24(2014)192—198www．tnmsC．cnMigrationbehaviorofsolidificationnucleiinpureA1meltundereffectofelectriccurrentpulsexi—binLI，Feng—guiLU，Hai—chaoCUI，Xin-huaTANGSchoolofMater

2、ialsScienceandEngineering，ShanghaiJiaoTongUniversity,Shanghai200240，ChinaReceived23February2013；accepted5July2013Abstract：Amathematicalmodelconsideringfreenucleiwasdevelopedtorevealthemigrationbehaviorofthefreenuclei．Numerica1simulationresultsshowthatmostofthenucleionthetopsurfaceofthemeltmovedow

3、nwardsanddistributerandomlyinsidetheAlmelt．whichinducesmorenucleationsitesresultingingrainrefinement．Atthesametime，theeffectofnucleisizeonthenucleidistributionandrefinementemployingelectriccurrentpulsefECP1wasalsoinvestigated．ThesmallernucleimigrateashortdistancewiththeA1meltatlowerspeed．Butforth

4、elargernuclei．themigrationdownwardswithhigherspeedbenefitstherefinementofinteriorgrainsofthemelt．TheresearchresultshelptobetterunderstandtherefinementprocessandprovideamorereasonableexplanationofthegrainrefinementmechanismusingECKeywords：electriccurrentpulse；solidificationprocess：grainrefinementm

5、echanism；migrationbehavior；numericalsimulationstructureofpureAlsystematicallyandprovedthatthe1IntrOductiOnnucleusrateincreaseswithapplyingtheECPduringtheinitialnucleationstageofthemeltandthattheECPElectriccurrentpulse(ECP)playsallimportantrolemakescrysta1nucleionthetopsurfaceofthemeltfaUinmateria

6、lsprocessing，especiallyinthefieldofmetaldownandmovefreelyinthemoltenmetal，whichsolidification『l一41．IthasbeentestifiedthattheECPcanpromotestherefinementofsolidificationstructure．effectivelyrefinethesoliditicationstructureofmetalHowevegamoredetailedexplanationaboutthematerials【5—10]，resultinginhigh

7、mechanicalpropertiesmigrationbehaviorofcrystalnucleiundertheefctofofmetallicmaterials『1l，121．Inrecentyears，moretheECPlackedexplicitresearch．Inourpreviousattentionshavebeenpaidtorevealingtherefinementstudyf20]，thetemper