Microstructural evolution in a non-cell forming metal

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1、Actametall,mater.Vol.41,No.5,pp.14211430,19930956-7151/93$6.00+0.00PrintedinGreatBritain.AllrightsreservedCopyright©1993PergamonPressLtdMICROSTRUCTURALEVOLUTIONINANON-CELLFORMINGMETAL:A1-MgD.A.HUGHESMaterialsDepartment,SandiaNationalLaboratories,Livermore,CA94550,U.S.A.(Received6Apr

2、il1992;inrevisedform30September1992)A~tract--MicrostructuralevolutioninAI+5.5at.%Mglightlydeformedbyrollingwasstudiedusingtransmissionelectronmicroscopy.ObservationsshowthatthedislocationsareorganizedintoaTaylorlatticecontainingmultipleburgersvectorsandhavingalternatingmisorientatio

3、nsalong{111}slipplanes.Theseobservationsareincontrasttotheusualdescriptionofthesestructuresas"random"dislocationtangles.Withincreasingstrain,agrainissubdividedintoseveraldomainsofdifferentlyorientedTaylorlattices.Thenewlyobservedboundariesbetweendifferentdomainsarelongsingledislocat

4、ionswallsformedalong'qIl1}.Asafurtherevolutionaryprogression,thesinglewalleddomainboundariesdevelopintomicrobands.Theobservedgrainsubdivisionparallelsthatobservedincellformingmetals.SubdivisionoccurstoaccommodatestrainusingfewerslipsystemsthanrequiredbytheTaylorcriterion.I.INTRODUCT

5、IONandmicrobands.ThisevolutionaryprocessandthetheoreticalinterpretationisconsistentforcellformingDuringdeformationofcellformingpolycrystallinemetals.metals,grainsaresubdividedintomisorientedregionsThecentralideathatgrainsaresubdividedintomis-inwhichdeformationoccursonfewerslipsystem

6、sorientedregionsshouldalsoapplytometalswhichdothanspecifiedbytheTaylorcriterionforstrainaccom-notformcells[4].Thisideaisinvestigatedforlightlymodation[1].TheselectionofactiveslipsystemsalsorolledA1+5.5at.%Mg.InAI+5.5at.%Mg,solutediffersbetweentheseregions.Longdensedislocationeffects

7、increasethefrictionstressandtherebyinhibitwalls(DDW)formtheboundariesbetweenthemis-cellformation.PreviousTEMstudiesshowthattheorientedregionsofequiaxedcells.ForpurenickeldislocationsubstructureofAI+5.5at.%Mgfollow-andaluminum,microbandsaresubsequentlyformedingsmallstraintensileorrol

8、lingdeformationcons