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MATERIALSSCIENCEANDENGINEERINGA527201019701974CONTENTSLISTSAVAILABLEATSCIENCEDIRECTMATERIALSSCIENCEANDENGINEERINGAJOURNALHOMEPAGEWWWELSEVIERCOM/LOCATE/MSEAEFFECTSOFHOTROLLINGPROCESSINGONMICROSTRUCTURESPROPERTIESOFMG3AL1ZNALLOYSHEETLA,B,A,BA,BA,BABARTICLEARTICLERECEIVEDRECEIVED11ACCEPTEDKEYWORDSAZ31HOTGRAINTWINNINGTEXTUREANDANDOFGRAIN1POSITIVETHISGRAINSAMPLESPERPASS1INTRODUCTIONMAGNESIUMSHEETISCURRENTLYBEINGTESTEDFORVARIOUSAPPLICATIONSHOWEVER,ROLLEDMGALLOYSOFTENEXHIBITRELATIVELYLOWSTRENGTHTO1MENTSALLOYSTHEBEENSHEETFROMTHATSTRESS,ISSUCHBETHEMODESSHANGHAIMGISKNOWNTODEFORMBYSLIP,TWINNINGANDGRAINBOUNDARYSLIDINGGBSGBSISPROBABLYAVAILABLEFORTHESUPERPLASTICDEFORMATIONORINTHENANOMATERIALS6,ANDITHASBEENOBSERVEDINFINEGRAINEDAZ31ASWELL79THEDISLOCATIONSLIPONBASAL09215093/DOIANDPOORFORMABILITYESPECIALLYATROOMTEMPERATUREDUETHEBASALORNEARBASALTEXTUREUSUALLYDEVELOPEDDURINGROLLINGFINEGRAINSANDRANDOMIZEDTEXTUREARETWOIMPORTANTREQUIREFORTHEAPPLICATIONOFMGALLOYSHEETTEXTUREEVOLUTIONINMGISAFFECTEDBYTHEINTERACTIONBETWEENTHESTRAINPATHANDINITIALMICROSTRUCTURE2,ANDTHEACTIVATIONOFBASALSLIPHASCONSIDEREDASTHEREASONFORTHEBASALTEXTUREINMGALLOY3ITWASALSOREPORTEDTHATTHEBASALTEXTUREORIGINATEDTHE1012EXTENSIONTWINNINGBASEDONTHEASSUMPTIONTWINNINGWOULDREORIENTTHECAXESPARALLELTOTHECOMPRESSIVESUPPORTEDBYEXPERIMENTS4ANDSIMULATIONS5WHILEITVERYDIFFICULTTOCHANGETHEBASALTEXTUREOFMAGNESIUMSHEET,ASAZ31ANDAZ61ALLOYS,THEINTENSITYOFTHEBASALTEXTURECANWEAKENEDANDTHEGRAINSIZECOULDBEREDUCEDBYCONTROLLINGROLLINGPROCESSINGIFTHECORRELATIONBETWEENTHEDEFORMATIONANDROLLINGPROCESSINGPARAMETERSCOULDBEESTABLISHEDCORRESPONDINGAUTHORATSCHOOLOFMATERIALSCIENCESANDENGINEERING,JIAOTONGUNIVERSITY,800DONGCHUANROAD,SHANGHAI,200240,CHINAEMAILADDRESSJJINLISJTUEDUCNLJINPLANESCANLEADTOLARGEPLASTICDEFORMATION,BUTTHEREAREONLYTWOINDEPENDENTBASALSLIPSYSTEMS10,11,FARFEWERTHANTHEFIVEINDEPENDENTSYSTEMSNECESSARYFORGENERALDEFORMATION12TWINNINGHASBEENCONSIDEREDPROVIDINGADDITIONALDEFORMATIONINMAGNESIUMAND10121011EXTENSIONTWINNINGAND10111012CONTRACTIONTWINNINGAREFREQUENTLYREPORTEDINMGANDMGALLOYS13INTHECASEOFDISLOCATIONSLIP,PRISMATIC10101120,ANDPYRAMIDAL10111120SYSTEMSCANBEOPERATEDINTHEAZ31ALLOYSINADDITIONTOSLIPINBASAL00011120SYSTEMFORTHEAZ31SHEETROLLEDATELEVATETEMPERATURES,NONBASALDISLOCATIONSLIPANDOTHERTWINNINGMODESAREEASILYACTIVATEDINADDITIONTOBASALSLIPANDEXTENSIONTWINNING,ANDTHEDEFORMATIONMODEINTHEAZ31ALLOYSHEETDURINGHOTROLLINGARESTRONGLYDEPENDENTONTHEINITIALGRAINSTRUCTUREANDTHEROLLINGPROCESSINGINADDITION,CONTINUOUSDYNAMICRECOVERYANDRECRYSTALLIZATIONCDRRHASBEENREPORTEDASAPHENOMENONFORTHEGRAINREFINEANDGROWTHINMGALLOYSDURINGDEFORMATIONATELEVATETEMPERATURES1415,ACCORDINGTOTHELOWENERGYDISLOCATIONTHEORYLEDS16HOWEVER,THECORRELATIONBETWEENTHEROLLINGPROCESSING,DEFORMATIONMECHANISMS,ANDTHEMICROSTRUCTUREEVOLUTION,ISNOTWELLUNDERSTOODFORTUNATELYTHEELECTRONBACKSCATTEREDDIFFRACTIONEBSDTECHNIQUEPROVIDESTHEPOSSIBILITYTOFOLLOWTHESEEFRONTMATTER2009ELSEVIERBVALLRIGHTSRESERVED101016/JMSEA200911047JIN,JDONG,RWANG,LMPENGNATIONALENGINEERINGRESEARCHCENTEROFLIGHTALLOYNETFORMING,SHANGHAIJIAOTONGUNIVERSITY,KEYSTATELABORATORYOFMETALMATRIXCOMPOSITE,SHANGHAIJIAOTONGUNIVERSITY,PRCHINAINFOHISTORY12APRIL2009INREVISEDFORMNOVEMBER200920NOVEMBER2009MGALLOYROLLINGREFINEMENTABSTRACTTHEMICROSTRUCTUREEVOLUTIONINVESTIGATEDTHEINITIALMICROSTRUCTUREAGEGRAINSIZEOF37H9262MDURINGTOEXTENSION,CONTRACTIONENTATION,GRAINSIZEANDROLLINGISTHEMAINMECHANISMCONTRACTIONAND1011ANDDOUBLETWINNINGHAVEALLOYDURINGHOTROLLINGIN400CLEDTOMOREUNIFORMTILITYTHANTHATOFTHESHEETTEMPERATURESANDLARGERANDTHEMECHANICALPROPERTIESANDMECHANICALPRCHINADEFORMATIONMECHANISMSOFAZ31ALLOYSHEETDURINGHOTROLLINGWEREINTHEASRECEIVEDAZ31SHEETSHOWSBASALTEXTUREWITHANAVERTHESUBSEQUENTHOTROLLINGPROCESSING,DISLOCATIONSLIPOCCURSINADDITIONDOUBLETWINNING,ANDTHETWINNINGMODEISDEPENDENTONTHEGRAINORITEMPERATURECONTINUOUSDYNAMICRECOVERYANDRECRYSTALLIZATIONCDRRREFINEMENTFORTHEAZ31SHEETDURINGHOTROLLING,ANDTHE1011012DOUBLETWINNINGACCELERATETHEREFINEMENTPROCESSCONTRACTIONEFFECTONGRAINREFINEMENTANDTEXTURERANDOMIZATIONFORTHEAZ31STUDY,HIGHERPERPASSREDUCTIONOF50ANDHIGHERROLLINGTEMPERATUREOFSTRUCTUREWITHMORERANDOMTEXTURE,WHICHRESULTEDINTHEHIGHERDUCROLLEDAT300CANDATPERPASSREDUCTIONOF30THEREFORE,HIGHERREDUCTIONROLLINGARERECOMMENDEDFORMICROSTRUCTUREOPTIMIZATIONIMPROVEMENTOFTHEAZ31SHEET2009ELSEVIERBVALLRIGHTSRESERVEDLJINETAL/MATERIALSSCIENCEANDENGINEERINGA5272010197019741971FIG1INITIALMICROSTRUCTURESOFAZ31ALLOYSHEETAIPFMAP,BPOLEFIGURESANDCSCHMIDFACTORFRACTIONSSUBJECTTOBASALSLIPSYSTEMEVOLUTIONOFTWINS,MISORIENTATION,TEXTUREANDGRAINSTRUCTUREOFTHEAZ31SHEETDURINGHOTROLLING,ANDTHEEVIDENCEFORUNDERSTANDINGTHEEFFECTOFDEFORMATIONMECHANISMSONTHEMICROSTRUCTURESEVOLUTIONTHISWILLOPENUPTHEPOSSIBILITYOFCONTROLLINGTHEMECHANICALRESPONSEBYDESIGNINGMICROSTRUCTUREAPPROPRIATETOROLLINGPROCESSINGTHEREFORE,THISPAPERAIMEDATTHEMICROSTRUCTURECORRELATION2ROLLING,WITHMICROSTRUCTUREINVERSETIONSNEARLYTHEIRDIRECTIONGRAINSFAVORABLERESPECTIVELY,INRESPECTIVELY473WASHEATEDDIRECTIONBARSAFTEREACHPASSANDSMALLSAMPLESWERETAKENFROMTHEQUENCHEDSPECIMENSFOREBSDANALYSISUSINGALEOTM1450SCANNINGELECTRONMICROSCOPEOPERATEDAT20KVFITTEDWITHATSLTMEBSDCAMERA17DUETOTHEDEFORMATIONSTRUCTUREINTHEEBSDSAMPLE,THEREISLOWINDEXQUALITYONTHEAREASWITHMOREDISLOCATIONREACTIONSANDFINERTWINS,BUTTHERESULTSSTILLCANGIVEALOTOFUSEFULINFORMATIONFIGPROCESSING,EVOLUTIONOFAZ31ALLOYDURINGHOTROLLINGUSINGEBSD,ANDTHEBETWEENTHEMICROSTRUCTUREANDMECHANICALPROPERTIESMATERIALSANDEXPERIMENTSTHEALLOYUSEDINTHISSTUDYWASAZ31ALLOYPRIORTOHOTTHEALLOYWASHOTEXTRUDEDAT573KTOARECTANGULARBARACROSSSECTIONOF110MM10MMFIG1SHOWSTHEINITIALOFTHEAZ31ALLOYBEFOREHOTROLLING,INCLUDINGTHEPOLEFIGUREIPFMAP,POLEFIGURESANDSCHMIDFACTORFRACTHERESULTSINDICATEAPRIMARILYBASALTEXTUREWITHTHECAXESPERPENDICULARTOTHESHEETPLANEANDONLYAFEWGRAINSWITHCAXESPARALLELTOTHESHEETPLANEANDTHEORIGINALEXTRUSIONEDFIG1CSHOWSTHESCHMIDFACTORVALUEOFMAJORITYISLESSTHAN03,SUGGESTINGTHATTHEGRAINORIENTATIONISNOTFORBASALSLIPTHEEXTRUDEDBARWASPREHEATEDAT573OR673KFOR05H,ANDTHENHOTROLLEDTOTHETHICKNESSOF35AND25MMHOTROLLINGMILLSATAGIVENREDUCTIONOF30OR50PERPASS,THETEMPERATUREOFTHEROLLERSWASCONTROLLEDATABOUTKUSINGINTERNALELECTRICHEATERSTHETOTALTHICKNESSREDUCTIONABOUT65AND75,RESPECTIVELYTHEROLLEDPLATESWEREREBETWEENPASSESTOMAINTAINTHEWORKABILITYTHEROLLINGWASPARALLELTOTHEEXTRUSIONDIRECTIONOFTHEASRECEIVEDTHEROLLINGSPECIMENSWEREWATERQUENCHEDIMMEDIATELY2ATHEDISTRIBUTIONOFGRAINSIZESOFAZ31ALLOYSHEETAFTERHOTROLLING13PASSAT300INWHICHGRAINSWEREDIVIDEDBYGRAINBOUNDARIESWITHMISORIENTATIONLARGER3RESULTSANDDISCUSSIONFIG2SHOWSTHEGRAINSIZEDISTRIBUTIONATVARIOUSPERPASSREDUCTIONSANDROLLINGTEMPERATURESTHEINITIALEXTRUSIONMATERIALHASCOARSEGRAINSRANGINGFROM10TO160H9262MANDANAVERAGEGRAINSIZEOF3729H9262MFIG2ASHOWSTHEGRAINSTRUCTUREEVOLUTIONAFTERROLLING1,2AND3PASSESATATEMPERATUREOF300CANDATAPERPASSREDUCTIONOF30AFTERTHESINGLEPASSROLLING,THEAVERAGEGRAINSIZEWASGREATLYREDUCEDWITHTHEMAJORITYOFGRAINSINTHE1030H9262MRANGEBUTACONSIDERABLEAMOUNTOFLARGEGRAINSRANGINGFROM40TO85H9262MAFTER2PASSESOFROLLING,THEGRAINSWEREMOREUNIFORMLYREFINEDWITHANAVERAGEGRAINSIZEOF88H9262MAFURTHERROLLINGPASSACTUALLYCAUSEDASLIGHTINCREASEOFGRAINSIZETO13H9262MSIMILARRESULTSWEREOBTAINEDATTHE400CROLLINGFIG2BSUMMARIZESTHEAVERAGEGRAINSIZESOFAZ31SHEETAFTERHOTROLLINGATVARIOUSPERPASSREDUCTIONSANDROLLINGTEMPERATURESTHERESULTSSHOWTHATATAGIVENROLLINGPASS,THEAVERAGEGRAINSIZESFORTHESHEETROLLEDAT400CARELARGERTHANTHATOF300CROLLEDSHEET,ANDTHATHIGHERPERPASSREDUCTIONLEDTOFINERGRAINSATTHESIMILARTOTALTHICKNESSREDUCTIONANDATSAMEROLLINGTEMPERATUREFIG3SHOWSTHEACTUALTENSIONPLOTSOFAZ31ALLOYSHEETBEFOREANDAFTERHOTROLLINGTHESTRESSSTRAINCURVESEXHIBITTHATTHEREAREWEAKERSTRAINHARDENINGBEHAVIORSANDHIGHERYIELDSTRESSYSANDULTIMATETENSILESTRENGTHUTSINROLLEDAZ31ALLOYSHEETTHANCWITHPERPASSREDUCTIONOF30,ANDBAVERAGEGRAINSIZESATVARIOUSROLLINGTHAN151972LJINETAL/MATERIALSSCIENCEANDENGINEERINGA527201019701974FIG3STRESSSTRAINCURVEOFAZ31SHEETBEFOREANDAFTERHOTROLLINGTHATINASEXTRUSIONSHEETTHEROLLINGAZ31SHEETSHAVESIMILARYSANDUTS,BUTHAVESIGNIFICANTDIFFERENCEINTHEIRDUCTILITY,WHICHISSUBSTANTIALLYHIGHERINTHESAMPLEAFTERHOTROLLINGATHIGHERTEMPERATURE150HIGHAND215ASINTHATCOARSETHEACCUMULATIONMORE1INORS,WHICHTHERANDTHEINOFPASSESITLUTIONANALYZEDBYEBSDATASMALLERSTEPSIZEOF05H9262M,ANDTHERESULTISSHOWNINFIG5FIG5AANDBSHOWSTHEIPFMAPSWITHTHELATTICEORIENTATIONANDGRAINSHAPEMAPSWITHDEFINEDTWINBOUNDARIESITCANBESEENFROMTHEFIGURESTHATTWINNINGNUCLEATEDINGRAIN1,2AND3,ANDTHETWININGMODEIS10121011EXTENSIONTWINNINGINGRAIN1,AND10111012DOUBLETWINNINGINGRAINS2AND3ACCORDINGTOTHETWINBOUNDARYDEFINITIONTHEPARENTGRAINS2AND3WEREDIVIDEDBYTHEDOUBLETWINS,ANDTHENTHEINITIALGRAINSWEREREFINEDTO3OR5FINERGRAINSASARESULTTHERESULTSSUGGESTTHATTHETWINNINGINTHISPROCESS,ESPECIALLYTHECONTRACTIONANDDOUBLETWINNING,ACCELERATESTHEPROCESSINGOFGRAINREFINEMENTTHETWININDUCEDPHENOMENONCOULDBEEXPLAINEDASFOLLOWINGMORETWINBOUNDARIESDEVELOPAFTERTWINNING,WHICHCOULDBETHEOBSTACLESFORDISLOCATIONSLIPDURINGSTRAININGTOWARDSTHETWINBOUNDARIESDENSITYOFDISLOCATIONSANDMISORIENTATIONSINCREASE,ANDATHIGHSTRAINS,HAGBSMAYDEVELOP,ANDTHENRESULTEDINTHEGRAINREFINEMENTASHUMPHREYSSAID15,DYNAMICRECRYSTALLIZATIONORIGINATESATHIGHANGLEBOUNDARIESREGARDLESSOFTHEDETAILSOFTHEMECHANISMOFNUCLEATIONBUTTHEGRAINNUCLEATIONANDGROWTHHEREMAYSTILLFOLLOWTHEMECHANISMOFCDRRWITHTHESUBGRAINFORMATIONANDTHENFINEGRAINWITHHAGBFIG6SHOWSTHEGRAINSHAPEMAPSWITHDEFINEDTWINBOUNDARIESOFTHEAZ31ALLOYSHEETAFTERROLLING3PASSESWITHPERPASSREDUCTIONOF30AT300CAND400C,ANDROLLING2PASSESWITHANDLARGERPERPASSREDUCTIONFIG4SHOWSTHEIPFMAPSOFAZ31ALLOYSHEETAFTERHOTROLLINGPASSAT300CAND30REDUCTIONANDAT400CWITH30ANDREDUCTIONS,RESPECTIVELYGRAINBOUNDARIESWEREDEFINEDASANGLEGRAINBOUNDARIESHAGBWITHMISORIENTATIONOF1590LOWERANGLEGRAINBOUNDARIESLAGBWITHMISORIENTATIONOF,ANDHAGBWASSHOWNASBLACKLINESANDLAGBWASSHOWNWRITELINESINTHEIPFMAPINFIG4THECALCULATEDGRAINSIZESFIG2AREFORTHOSEGRAINSDIVIDEDBYHAGBFIG4ASHOWSTHEMICROSTRUCTUREWASPROGRESSIVELYREFINEDALTHOUGHSOMEGRAINSREMAINEDAFTERTHE30ROLLINGREDUCTIONAT300CFINEGRAINSFORMTYPICALNECKLACESTRUCTURESDUETOTHESTRAINDURINGROLLINGWHICHLEADTOCDRRINTHESEREGIONSCOARSEGRAINSWEREOBSERVEDINFIG4BANDCAFTERROLLINGPASSAT400CWITHPERPASSREDUCTIONOF30AND50ASSHOWNFIG4C,ALARGENUMBEROFLAGBSINTHECOARSEGRAININTERIARELIKELYTHERESULTOFTHEDISLOCATIONSLIPANDINTERACTIONS,COULDDEVELOPINTOHAGBANDGRAINREFINEMENTDURINGFURDEFORMATIONACCORDINGTOTHECONTINUOUSDYNAMICRECOVERYRECRYSTALLIZATIONCDRRMODEL14,15THISISCONSISTENTWITHDATAINFIG2BTHATTHELARGERAVERAGEGRAINSIZESWEREOBTAINEDTHESHEETAFTER1PASSROLLINGAT400CANDATPERPASSREDUCTION50BUTTHEFINESTAVERAGEGRAINSWEREOBSERVEDAFTERROLLING2ATTHISCONDITIONFIG4ALSOSHOWSSOMETWINNINGSITESDURINGTHEHOTROLLING,BUTISDIFFICULTTOIDENTIFYTHETWINNINGMODESDUETOTHELOWERRESOTHEMICROSTRUCTUREASSHOWNINTHEBLACKBOXINFIG4CWASFIG4IPFMAPSOFAZ31ALLOYSHEETAFTERROLLINGATA300CWITHREDUCTIONOF30,PERPASSREDUCTIONOF50AT400C,RESPECTIVELYTHEGRAINSIZEISLARGERINFIG6BCOMPAREDTOFIG6AANDC,INDICATINGTHATTHEGRAINSWEREREFINEDFURTHERBYHIGHERPERPASSREDUCTIONROLLINGANDATALOWERTEMPERATURETHEFACTTHATSMALLERGRAINSIZEISFOUNDATHIGHERREDUCTIONISDUETOSTOREDENERGYOFDEFORMATIONBEINGHIGHERWHICHLEADSTOHIGHERDRIVINGFORCEFORNUCLEATIONANDHENCEFINERGRAINSIZEATTHELOWERTEMPERATURETHESOFTENINGRATEISSLOWER,HENCELEADSTOHIGHERWORKHARDENINGANDLARGERDRIVINGFORCEFORNUCLEATIONOFGRAINS,ANDHEREGRAINGROWTHISALSOSLOWINADDITION,CONTRACTIONTWINS,DOUBLETWINSANDEXTENSIONTWINSWEREOBSERVEDINTHELARGERGRAINSINFIG6,ANDTHEREISAHIGHERVOLUMEFRACTIONOFCONTRACTIONTWINSANDDOUBLETWINSTHANTHATOFEXTENSIONTWINS,ESPECIALLYTHEREARELESSEXTENSIONTWINSATTHEHIGHERROLLINGTEMPERATUREFIG6ALSOSHOWSTHATTHETWINNINGMODEISDEPENDENTONTHEGRAINSIZETWINNINGISMOREVISIBLEINTHEPARENTGRAINSWITHGAINSIZELARGERTHAN20H9262M,HOWEVER,FEWORNOTWINSWEREOBSERVEDINSMALLERGRAINSASSHOWNINFIG6CASSHOWNINFIG1,THEINITIALGRAINORIENTATIONSOFTHEAZ31ALLOYSHEETARENOTFAVORABLEFORTHEDISLOCATIONSLIPONTHEBASALPLANEINADDITION,THEMAJORITYOFTHEGRAINSHAVETHEIRCAXISPARALLELTOTHECOMPRESSIVESTRESS,WHICHISNOTFAVORABLEFORTHEEXTENSIONTWINNINGINTHOSEGRAINSBUTTHEBASALSLIPISSTILLTHEMAINDEFORMATIONMODEDUETOTHELOWESTCRITICALRESOLVEDSHEARSTRESSCRSS,ANDALSOTHECONTRACTIONTWINNINGCANBEPOSSIBLYACTIVATEDASCRIBETOTHECAXESOFTHOSEGRAINSUNDERCOMPRESSIONINTHECASEOFAFEWGRAINS,BLUEORGREENGRAINSINFIG1AWITHTHEIRCAXESPARALB400CWITHREDUCTIONOF30ANDC400CWITHREDUCTIONOF50LJINETAL/MATERIALSSCIENCEANDENGINEERINGA5272010197019741973FIG50,AWITHDOUBLEREFERENCESARTICLEFIG400LELGENERALLYTHEEXTENSIONEXTENSIONTRACTIONINMISORIENTATIONISFORFAVORABLESYSTEMSIONDURINGBLEWITHTHANINROLLINGTRACTIONAND5MICROSTRUCTURESOFAZ31ALLOYSHEETROLLED1PASSAT400CWITHREDUCTIONOFDEFINEDTWINBOUNDARIES,EXTENSIONTWINBOUNDARIES8612105AREOUTLINEDTWINBOUNDARIES3812105OUTLINEDINBLUEFORINTERPRETATIONOFTHE6GRAINSHAPEMAPSWITHTWINBOUNDARIESOFAZ31ALLOYSHEETAFTERROLLINGA3PASSESCWITHPERPASSREDUCTIONOF50INWHICHTHETWINBOUNDARIESWEREDEFINEDASSAMETOSHEETPLANE,1012EXTENSIONTWINNINGISEASILYOCCURREDTHEEXTENSIONTWINNINGWILLBEREORIENTEDTO86FROMINITIALSTATUS13,AND,THEPARENTGRAINWILLBEREPLACEDBYTHETWINSDUETOTHEFASTTWINGROWTHINTHENEWTWINSAFTERTWINNING,ONLYDISLOCATIONSLIPONBASALPLANEANDCONTWINNINGAREPOSSIBLEDUETOTHENEWGRAINORIENTATIONTHECASEOF1011CONTRACTIONTWINNING,THETWINSHAVEAOF56WITHTHEPARENTGRAINS,ANDTHECONTRACTIONTHINNERANDLONGERTHANEXTENSIONTWINSAND,THUS,ISDIFFICULTTWINGROWTHHOWEVER,THENEWGRAINORIENTATIONSAREMOREFOREXTENSIONTWINNINGANDDISLOCATIONSLIPONBASALSLIPAFTERCONTRACTIONTWINNINGTHEREFORE,THE1012EXTENTWINNINGALWAYSFOLLOWSTHE1011CONTRACTIONTWINNINGDEFORMATIONINMGALLOY,IE,THE10111012DOUTWINNINGTHEDOUBLETWINSHAVEMISORIENTATIONOFNEAR38THEPARENTGRAIN13ASARESULT,THEREAREMOREDOUBLETWINSCONTRACTIONTWINSINTHEAZ31SHEETAFTERHOTROLLINGASSHOWNFIG6ASSHOWNINFIG7,THETWINNINGMODESAREALSODEPENDENTONTHETEMPERATUREFIG7CSHOWSTHEVOLUMEFRACTIONOFTHECONANDDOUBLETWINSINTHEAZ31ALLOYSHEETAFTERHOTROLLING,THEHIGHESTVOLUMEFRACTIONOFDOUBLEANDCONTRACTIONTWINSIPFMAPANDTHELATTICEORIENTATIONOFTHEPARENTANDTWINS,BGRAINSHAPEMAPINRED,CONTRACTIONTWINBOUNDARIES5612105OUTLINEDINGREENANDTHETOCOLORINTHISFIGURELEGEND,THEREADERISREFERREDTOTHEWEBVERSIONOFTHEAT300C,B3PASSESAT400CWITHPERPASSREDUCTION30,ANDC2PASSESATASTHATINFIG5WASFOUNDINTHESHEETAFTERROLLING3PASSESAT400CWITHTHEPERREDUCTIONOF30,WHILETHELOWESTVOLUMEFRACTIONINTHESHEETAFTERROLLING3PASSESAT300CWITHSAMEPERPASSREDUCTIONTHERESULTSSUGGESTTHATCONTRACTIONANDDOUBLETWINNINGAREREADILYACTIVATEDATHIGHERROLLINGTEMPERATURES,WHICHCOULDBEASCRIBETOTHELOWERCRSSFORTHECONTRACTIONANDDOUBLETWINNINGATHIGHERTEMPERATUREASSIMILARASTHECRSSFORNONBASALDISLOCATIONSLIPCOMPARINGFIG7THEVOLUMEFRACTIONOFCONTRACTIONANDDOUBLETWINSINTHEAZ31SHEETAFTERHOTROLLING1974LJINETAL/MATERIALSSCIENCEANDENGINEERINGA527201019701974FIG80001POLEFIGURESOFAZ31ALLOYSHEETAFTERROLLINGA3PASSESAT300C,B3PASSESAT300CWITHPERPASSREDUCTION30AT400C,ANDC2PASSESAT400CWITHPERPASSREDUCTIONOF50TOBASALDISLOCATIONSLIP18ONTHEOTHERHAND,THE1011CONTRACTIONAND10111012DOUBLETWINNINGAREREORIENTEDFROMTHEBASALPOLESTO56AND38REFERENCETOINITIALSTATUS,ANDTHEREFORETHEACTIVATIONOFTHECONTRACTIONANDDOUBLETWININGINTHEAZ31SHEETCANRESULTINTHEWEAKENINGOFTHEBASALTEXTUREFIG8ISTHE0001POLEFIGURESOFAZ31AFTERHOTROLLING,SHOWINGBROADERSHEETHOWEVER,LIMITEDTWOANDSTRUCTUREBUTWEREINTENSITYDOUBLEACCOMMODATETEXTURERANDOMIZATION,HIGHERPERPASSTEMPERATURESTHEOBSERVEDABOVE4STILLDUEEXTENSIONTOTOANDTIONDURINGTHEPARENTVATEDOFTWINNINGTWINNING,EXTENSIONCONTRACTIONREFINEMENTANDTEXTURERANDOMIZATIONFORTHEAZ31ALLOYDURINGHOTROLLINGINTHISSTUDYATAGIVENROLLINGREDUCTION,THEAVERAGEGRAINSIZEOFAZ31SHEETROLLEDAT400CWASLARGERTHANTHATOFTHESHEETSAMPLESROLLEDAT300C,ANDATSAMEROLLINGTEMPERATUREHIGHERPERPASSREDUCTIONLEDTOFINERGRAINSIZEINTHESHEETMATERIALS101112131415161718DISTRIBUTIONOFBASALPOLEANDWEAKERBASALTEXTUREINAZ31ROLLEDAT400CCOMPAREDTOTHESAMPLESROLLEDAT300CTHECHANGEINGLOBALTEXTUREISINSIGNIFICANTDUETOTHEVOLUMEFRACTIONOFTWINNEDMATERIALASMENTIONEDBEFORE,FINEGRAINSANDRANDOMIZEDTEXTUREAREIMPORTANTREQUIREMENTSFORIMPROVEDMECHANICALPROPERTIESTHEAPPLICATIONSOFTHEMGALLOYSHEETINTHISSTUDY,THEGRAINCANBEEFFECTIVELYREFINEDATLOWERROLLINGTEMPERATURES,MOREEXTENSIONTWINNINGANDDISLOCATIONONBASALSLIPSYSTEMOBSERVEDINTHISCONDITION,RESULTINGINHIGHERBASALTEXTUREATHIGHERROLLINGTEMPERATURES,MORECONTRACTIONANDTWINNINGCANBEACTIVATEDANDTHENONBASALSLIPALSOWOULDLARGERPLASTICDEFORMATION18,WEAKENINGTHEBASALTHUS,HIGHERROLLINGTEMPERATURESAREFAVORABLEFORTEXTUREBUTLEADTOLARGERGRAINSATGIVENPERPASSREDUCTIONTEMPERATUREROLLINGRESULTEDFORTUNATELY,ROLLINGATHIGHERREDUCTIONCANOFFSETTHELARGEGRAINSIZETHEREFORE,HIGHERANDLARGERPERPASSREDUCTIONSARERECOMMENDEDFORAZ31SHEETALLOY,TOACHIEVEBETTERMECHANICALPROPERTIESTHEHIGHDUCTILITYINFIG3PROVIDESAGOODEXAMPLEBASEDONIDEACONCLUSIONSINSUMMARY,ITWASFOUNDTHATDISLOCATIONSLIPONBASALPLANEISTHEMAINDEFORMATIONMODEINAZ31SHEETDURINGHOTROLLINGTOTHEINITIALMICROSTRUCTUREWITHBASALTEXTURETHE1012TWINNINGOCCURREDINGRAINSWITHTHEIRCAXESPARALLELSHEETPLANEANDTHEEXTENSIONTWINNINGREORIENTEDTHEGRAINS86FROMTHEIRINITIALSTATETHE1011CONTRACTIONTWINNING10111012WEREACTIVATEDATLARGERTHICKNESSREDUCBECAUSETHECAXESOFMAJORITYGRAINSWEREUNDERCOMPRESSIONROLLINGTWINNINGISALSODEPENDENTONINITIALGRAINSIZEANDROLLINGTEMPERATURE,TWINNINGISREADILYOBSERVEDINTHELARGERGRAINSANDMORECONTRACTIONANDDOUBLETWINNINGAREACTIATHIGHERROLLINGTEMPERATURESCDRRISTHEMAINMECHANISMGRAINREFINEMENTFORTHEAZ31SHEETDURINGHOTROLLING,BUTTHEINTHISPROCESS,ESPECIALLYTHECONTRAC