modeling the effects of mold topography on aluminum cast surfaces

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1、SolidicationofAluminumAlloysEditedbyTMS(TheMinerals,Metals&MaterialsSociety),2004ModelingtheEectsofMoldTopographyonAluminumCastSurfacesLijianTan1,NicholasZabaras11MaterialProcessDesignandControlLaboratory,188FrankH.T.RhodesHall,CornellUniversity,Ithaca,NY1485

2、3,USAKeywords:AluminumSolidication;Moldtopography;CastSurfacesAbstractTheair-gapnucleationtime,thestressevolutionandthesolidshellgrowthpatternareexaminedfordierentmoldtopographiestoillustratethepotentialcontrolofaluminumcastsurfacemorphologiesduringtheearlyst

3、agesofsolidicationusingproperdesignofmoldtopographies.Theinteractionbetweenheattransferanddeformationduringtheearlystagesofsolidicationisconsideredinthiswork.Simulationresultsshowthatasinusoidalmoldsurfacewithasmallerwavelengthleadstoanearliernucleationofair-

4、gaps.Inaddition,theunevennessinthesolid-shellgrowthpatterndecreasesfasterforasmallerwavelength.Suchstudiescanbeusedtotunemoldsurfacesforcontrolofcastsurfacemorphologies.IntroductionStudyofthermalstressanddeformationdevelopmentduringaluminumcastingintheearlystag

5、esofsolidicationcanbeanimportanttoolforunderstandingtheformationofcracks,liquationorotherdefectsintheingotsurface.Sincethemaindrivingforceofthermalstressdevelopmentinasolidifyingbodyisthetemperaturereductionprocess,controloftheheatextractionthroughthemold-shel

6、linterfaceduringtheearlystagesofsolidicationisoneofthemostchallengingandimportantproblemsassociatedwithaluminumcasting.Incurrentpracticessurfacedefectsareremovedthroughexpensivesurfacemillingandscalpingprocesses.Understandingtheeectofmoldtopographyontheheatex

7、tractionprocessandtheresultingshellgrowthmayallowcertaincontrolofcastsurfacemorphologiesandthusleadtoareductionofunnecessarypost-castingoperationsneededtoremovesurfacedefects.Theanalysisofthedeformationofasolidifyingbodyissignicantlydierentfromthatofastandard

8、xedbody.ThiswasrstdiscussedbyRichmond[1]andimplementedin[2,3]andintwo-dimensionalplanestressandaxisymmetricapplicationsbyZabarasetal.[4,5].Theseeortsemphasizetheneedtoinc