az31镁合金轧制箔材微成形尺寸效应的研究

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1、哈尔滨工业大学工学硕士学位论文AbstractWiththegrowingrequirementforminiaturizedproduct,miniaturizedtechnologyhasaconstantdevelopmentinrecentyears.Gasblowmicro-bulgingisamicroplasticformingtechnologywithexcellentcharacteristicssuchaslowcost,withoutterracedie,particularlyforquantit

2、yproduction.People'sconcernisgraduallyarousedbytheresearchongasblowmicro-bulging.Microplasticforminghasdifferentcharacteristicscomparedwithmacroplasticforming,whichiscalledsizeeffectphenomenon.Inthispaper,aseriesofexperimentsarecarriedouttostudythesizeeffectphenom

3、enonofAZ31magnesiumalloyrolledfoilinmicro-tensileatroomtemperatureandgasblowmicro-bulging.ThetensiletestsofAZ31magnesiumalloyrolledfoilareperformedatroomtemperaturetostudythesizeeffectonfoilthickness,grainsizeandstrainratetoflowstress.Theexperimentalresultsshowtha

4、tthetensilestrengthesoftensilesamplesarelessthanthatofthemacro-tensilesamplesinthesamecondition,whichisthesizeeffectphenomenon.ThetensilestrengthforrolledfoilofAZ31magnesiumalloyisnotsensitivetothestrainrateatroomtemperature.Theperformanceofthesizeeffectphenomenon

5、inmicro-tensiletestsisthathigherstrengthandelongationcouldbeacquiredbylargerthicknessandsmallergrainsize.Thesizeeffectofthemechanicalpropertiescouldbeinterpretedbythemodelwhichisestablishedonthebasisofthesurfacelayerandthesizeeffectoftheelongationcouldbeinterprete

6、dbytherelationshipbetweentheinternalstrainandthedeformationofgrainboundary.Thegasblowmicro-bulgingexperimentforAZ31magnesiumalloyrolledfoiliscarriedouttostudythesizeeffectcausedbythefoilthickness,thediameterofdiecavityandinitialgrainsize.Itisfoundthattheflowstress

7、inmicro-bulgingislargerthanthatinthemacro-bulging,theflowstressislargerwhenthediediameterissmallerandthefoilthicknessisthinner,theflowstressincreasedwiththeinnergrainsizedecreasedwhichisthesameasthephenomenoninthemacro-bulging;howeverthedifferenceinthestressbetwee

8、ndifferentgrainsizeisdecreasedwhenthestrainissame.Abovephenomenonisthesizeeffectphenomenonwhichcanbe-III-哈尔滨工业大学工学硕士学位论文explainedbythestraingradienthard