45.The influence of back pressure on ECAP

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1、ActaMaterialia55(2007)2985–2993www.elsevier.com/locate/actamatTheinfluenceofbackpressureonECAPprocessedAA6016:Modelingandexperimenta,*abP.W.J.Mckenzie,R.Lapovok,Y.EstrinaDepartmentofMaterialsEngineering,MonashUniversity,Clayton,Vic.3800,AustraliabInstitutfu¨rWerkstoffkund

2、eundWerkstofftechnik,TechnischeUniversita¨tClausthal,Agricolastr.6,38678Clausthal-Zellerfeld,GermanyReceived14June2006;receivedinrevisedform18December2006;accepted21December2006Availableonline27February2007AbstractAgeneralizedthree-dimensionaldislocation-density-basedtwo

3、-phasecompositemodelhasbeenfurtherdevelopedtoincorporatetheeffectsofhydrostaticpressureduringsevereplasticdeformation.Itwasappliedtoequalchannelangularpressingofwroughtaluminiumalloy6016withappliedbackpressure.Itwasshownthatthetwo-phasecompositemodelapproachwithadditiona

4、ltermsaccountingforthepresenceofhydrostaticpressureisadequateforpredictingthecellsizeofanultrafine-grainedmaterialandalsoprovidesadescriptionofthedislocationdensityevolution.Theeffectofbackpressureistoincreasetheresultantdislocationdensityinboththecellwallsandthecellinter

5、iors.Aconcomitantincreaseofthecellwallthicknessandcellwallvolumefractionand,notably,adecreaseintheresultantaveragecellsizewasalsopredicted.CrownCopyrightÓ2007PublishedbyElsevierLtd.Allrightsreserved.Keywords:Equalchannelangularpressing;Aluminiumalloy6016;Backpressure;Tw

6、o-phasecompositemodel;Dislocationcellsize1.Introductiontotheprocessedmaterial,finite-elementsimulationandmanyexperimentalobservations(includingtheuseofAstheinvestigationofsevereplasticdeformation(SPD)scribedgrids[8])haveshownthattheactualstress–strainofmetallicmaterialsg

7、ainsmomentum[1],thepotentialfordistributionisnon-uniformandthedeformationisnotsim-suchtechniquestoproduceultrafine-grained(UFG)struc-pleshear[9].ManyyearsofresearchatMonashUniversityturesinbothbulk[2]andsheetmaterial[3]atasemi-con-ontheeffectofhydrostaticpressureduringECA

8、Phavetinuousindustriallevelisappreciatedmoreandmore.Itisshownthattheuniformityofthestressandstraindistribu-bec