TECHNICAL NOTE 4082 - UNT Digital Library/67531/metadc57096/m... · ‘4...

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ABNORMALGRAINGROWTHIN NICKEL-BASE

HEAT-RESISTANTALLOYS

By R. F. Decker, A. I. Rush, A. G. Dane,and J. W. Freeman

University of Michigan

WashingtonDecember 1957

TECHNICAL NOTE 4082

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TECHLIBRARYKAFB,NM

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TECHNICALNOTE4092

AE!NORMALGRAINGR~TH INNICKEL-EASE

HEAT-RESISTANTALLOYS

ByR.F. Decker,A. I.Rush,A. G.Dane,andJ.W. Freeman

SUMMARY

A laboratorystudywascarriedouttoestablishthebasiccausesofabnormalgraingrowthinair-andvacuum-meltedWaspaloy,InconelX-550,andNimonic80Aalloys.Allof theresultsindicatedthatsmallreductionsofessentiallystrain-freemetalwerethebasiccauseofabnormalgraingrowth.Eetweenreductionsof 0.4and5.0percent,inmostcases,therewasa narrowrangeof reductionsresponsibleforabnormalgrowth.Ina fewspecialcasestheresponsiblereductionswereas lowas 0.1percentandashighas 9.7 percent.

Thepreventionofabnormalgraingrowthclemlyrequiresavoidanceof smallcriticalreductions.Themainproblemis taanticipateandtoavoidconditionsleadlngtocriticaldeformation.Insuringthatallpartsofa metalpiecereceivemorethan5- to 10-percentreductionwill

. preventit. Nonuniformmetalflowduringhot-workingoperationsisprobablythemajorsourceofabncnmslgraingrowth.Anysmallreduction,particularlyif it includesa straingradientso thatthecriticalreduc-.* tionwilldefinitelybe present,isa ccmmonsource.Strainsarisingfromthermalstressesduringrapidcoolingcandevelopsusceptibility.Removalof strainby recrystallizationduringworkingfollowedby a smallfurtherreductioncan,in certaincases,induceabnormalgraingrowthinthepresenceoflargereductions.

Thephenomenonofabnormal-in growthisremarkablyindependentoftemperatureofworkingandofheatingtemperatures.Iftheheatingtemperatureandtimearesufficientforabnormalgraingrowth,highertemperaturesincreasethegrainsizeonlyslightly.Priorhistoryofthealloysbeforecriticalstrainingalsohasrelativelylittleeffect,providedthepriortreatmentreducesstrainbelowthecriticalamount.Certainconditionsofworkingorheatingseemedtominimizeabnormalgraingrowth.These,however,donotappeardependableforcontrollingabnormalgraingrowthbecauseof theprobabilitythattheireffectivenessis dependentonpriorhistory.

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Theinfluenceofalloycompositionseemstobemainlyinvariation &oftheexcessphaseswhichrestrictgraingrowth.A scmewhatsmallergrainsizeinvacuum-meltedthaninair-meltedWaspaloywasapparentlyduetomoregrain-growthrestrainersresultingfroma highercarbon %“content.InconelX-550didnotundergoabnormalgraingrowthat1,950°Fas didWaGpaloyandNimonic8QAalloys.At 2,150°F, thenormalsolutiontemperatureforInconelX-550,itdidoccur.ApparentlythemorestablecolumbiumcompoundsinInconelX-550restrainedgraingrowthtoa highertemperaturethanthelessstablegrowthrestrainersintheotheralloys.

INTRODUCTION

A studyofthecausesofabnormallylargegrainsforminginnickel-baseheat-resistantalloysduringhot-workingorsubsequentfinalsolutiontreatmentwascarriedout. ThealloysinvestigatedwereWaspaloyandInconelX-550.Vacuum-meltedWaspaloy,reputedtobe lesssusceptibletograingrowth,aswellasair-meltedmaterial,wasincludedintheinvesti-gation.A Mmitedmount of dataforNimonic8QAalloyisincludedfromanotherinvestigation(reportedIna privatecaummnication).Onepreviousreport(ref.1)presentedpreliminaryresultsfora similarstudyofS-816alloy.

Theobjectiveoftheinvestigationwastoestablishthefundamentalprinciplesgoverningtheformationofabnormallylargegrainsduringhot-workingandfinalheattreatmentinheat-resistantalloysofthetypes .usedinthegasturbinesof jetengines.Forpurposesofthisinvesti-gation,anygrainslargerthanASIM1 wereconsideredabnormallylarge.Furthermore,theinvestigationwasmainlylimitedb normalconditions

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ofheatingforhot-workingandforheattreatment,ithavingbeenwellestablishedthattheabnormalgraingrowthofinterestoccurredundertheseconditions.Howeverja fewexperimentsinvolvingtemperatures

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higherthannormalwereIncluded.

Thepresenceofabnormallylargegrainshasbeenassociatedwithpoorpropertiesinheat-resistantalloys,particularlywithlowfatiguestrengthandbrittlenessundercreep-ruptureconditions.Theconsequentnecessarygrain-sizecontrolisa recurringprobleminmakingforgingsandotherhot-workedproductsfromtheheat-resistantalloysusedinair-craftgasturbines.Inpractice,procedures.forhot-workingareeventu-allydevelopedwhicheliminateorminimizegrain-sizeproblems.Thosedevelopedhavegenerallybeenempiricalandhavenotdefinedthebasicprincipleinvolved.ThedataincludedinthisreportforNimonic80Aalloy,forinstance,representexperimentscsrriedouttohelpclarifya productionproblemofgrain-sizecontrolinanalloywhichhasbeenextensivelyused.

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Thegeneralprocedureoftheinvestigationwasto carryoutcon-trolledlaboratoryexperimentson samplesofbarstocktofindconditionsofheatingandhot-workingwhichresultedinabnormalgraingrowth.Liketheinvestigationons-816alloy(ref.l),thisinvestigationdidnotdiscloseanyconditionsforabnormalgraingrowthotherthanby smallamountsofcriticaldeformation.Theinvestigationdoes,however,definemanyconditionswhichleadto suchcriticaldeformationwhicharenotsoobviousas simplesmallamountsof deformationduringhot-working.

Theinvestigationwascarriedoutby theEngineeringResearchInstituteof theUniversityofMichiganunderthesponsorshipandwiththefinancialassistanceoftheNationalAdvisoryCommitteeforAeronautics.Themembersof theNACASubcommitteeonPowerPlantMaterialsassistedintheplanningoftheexperimentalprogrm,particularlyby definingcondi-tionsofworkingwheregrain-gowthproblemshadbeentroublesome.

PROCEDURES

Thegeneralproceduresusedto establishconditionsleadingto abnor-malgraingrowthwereas follows:

(1)Commerciallyproducedbarstockwasusedforexperimentalmate-rials.Theonlyexceptionsweresmallcommerciallyproducedingotsofvacuum-meltedWaspaloyrolledtobarstockat theUd.versityofMichigan.

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(2)Mostof theas-receivedbarstockwasnotsuitableforexperi-mentalresearchbecauseof unevengraing,rowthor susceptibilitytoabnormalgraingrowthduringreheatingtohot-workingor solution-treatingtemperatures.Accordingly,moststockwasgivenan “equalizingtreatment”designedtoproducea uniformreasonablyfinegrainedmaterialforexperi-mentalpurposes.Thistreatmentusuallyconsistedof:

(a)A fairlyheavyreductionby rolling

(b)A heattreatmentof1 hourat theusualsolution-treatingtemperatureforthealloy

Thecoolingaftertheequalizingheattreatmentwasperfonnedbyeitherair-coolingoroil-quenching.Water-quenchingmadeallof thealloyssusceptibletoabnormalgraingrowthon thesurfaceofthebars.In somecasesevenair-cooledalloysdevelopedsomesusceptibilitytosuchgrowth.An equalizingheattreatmentwas,however,necessary.Otherwise,theinitialuneven-grain-growthcharacteristicscouldmasktheinfluenceof theexperimentalconditionsusedto obtainabnormalgraingrowth.

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Theconditionsoftheequalizingtreatmentweresometimesdeliberately ●

varied,orthetreatmentsomitted,to studytheinfluenceofsuchfactorsonabnormal-grain-growthcharacteristics. -—

%(3)Repeatedheatingandcoolingwasusedto studytheabnormalgrain

growthinducedby thermalstressesalone.Water-quenching,oil-quenching,andair-coolingwereusedtovarythecoolingrateandresultantthermalstre~ses.

(4)TheinfluenceofamountandtemperatureofworkingwasstudiedbyrollingtaperedspecimenstoflatbarsbetweenopenrollsIna rollingmill. Thetaperedspecimenswereusuallymachinedfromtheequalizedstock. Twosizesof specimens(fig.1)wereusedtogivereductionsrangingfromO toabout15 or29percent..Thespecimenswereplacedinafurnaceat thetemperatureselectedforrollingandheldinthefurnace1/2hourbeforerolling.Inmostcases,onlyonepassthroughtherollswasused. Thespecimenswereair-cooledfromtherollingoperation.

A fewexperimentswerecarriedoutusingtensilespecimensto obtainuniformreductiontostudythecomparativeeffectsofuniformstrainandthestraingradientsfromthetaperedspecimens.

(5) Therolledspecimenswereheatedtotheusualsolution-treatingtemperaturesfortheusualtimesforgraingrowthtooccur.Insomecases,thespecimenswerecutintotwopiecesparalleltothedirectionofrollingbeforesolutiontreatment.Onehalfwasexaminedintheas-rolledcondi-tionandtheother,aftersolutiontreatment.

(6) Thespecimenswerethencarefullymeasuredandthereductionincross-sectionalsreacomputed.Thespecimensweresectionedandexaminedmicroscopicallyforgrainsizealongthelengthsoftherolledbars.

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(7)me grain-Si.Zeratingsystemusedwasthatestablishedby theAmericanSocietyforTestingMaterials(ref.2). ItwasnecessarytoextendthissytemtolargersizesthannumberO throughthenotation-1to -5grainsizes.Theactualgrainsizesinvolvedwereasfollows:

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NACAKill40!32 5

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ASTMgrainsize Grains/sq in.of Approximatedism.imageat 100diam. ofgrains,in.

8 128 0.000g7’ 64 .00126 32 .00185 16 .00254 8 .00353 4 .0052 2 .0071 1 .0100 ●5 .014

-1 .25 .020-2 .125 .028

.0625 .040:? .0312 .056-5 .0156 .080

Inreportinggrainsizes,thecompleterangeisgiveninthetablesofdata. Thegraphicalpresentationsaregenerallylimitedtothemaximumsize.

EXPERIMENTALMATERIALS

Theexperimentswerecarriedoutonbarstockcommerciallyproducedfromair-meltedheats,withtheexceptionofthevacuum-mel~dWaspaloy.Theinformationfurnishedby thesuppliersof thetestmaterialsis giveninthefollowingsections.

WaspaloyAlloy

Theair-meltedWaspaloyalloywassuppliedgratisby theAlleghenyLudlumSteelCorp.as l-inch-squarebarstockmadefra a 9-inchingotfromheat43638.Thevacuum-meltedWaspaloywassuppliedgratisby theUticaDropForgeandToolCorp.as a 2-inch-dismeteringotfrcmheat3-259.Thechemicalanalysessuppliedby theproducerswereasfollows:

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Chemicalcomposition,weightpercent

c Mn Si Cr Ni co Mo Ti Al Fe Cu s P

Heat43638

0.03 1.14 0.63 18.8 Balance13.7 3.15 2.56 1.43 1.18 9.11 0●0150.016

Heat3-259

0.050.27 0.57 19.8 Ealance13.8 3.90 3.17 1.15 0.69 .10 0.005 -----

n

-i

Thesmallingotsofvacuum-meltedstockwerehot-rolledat 1,950°Fto 3/4-andl/2-inchbarsat theUniversityofMichigan.

InconelX-550Alloy

TheInconelX-550stockwasfurnishedgratisby theInternationalNickelCo.,Inc.,ashot-rolled2*-by 1~-inchflatbarsfromheatY7180x.

Theonlyotherinformationsuppliedwasthefollowingreportofchemicalcomposition:

Chemicalcomposition,weightpercent

c Mn Fe s Si Cu Ni C!r Al Ti TaandCb

0.05 0.7’36.59 O.oq’ 0.280.03 72.63 14.97 1.16 2.50 1.0>

TheNimonic80Aalloywasintheformofl-inch,hot-rolled,center-less,groundbarstockwhichhadbeenpurchasedby theContinentalAviationsndllngineeringCorp.frcmconunercialair-meltedheat5331Bmadeby theInternationalNickelCo.,Inc.

Thefollowingreportofchemicalcompositionwassupplied:

Chemicalcomposition,.weightpercent

c Mn Fe s Si Cu Ni Cr Al Ti

o.~ 0.55 0.59 0.007 0.34 O.m Balance20.5 0.98 2.20

..

A

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FACTORSINFLUENCINGGRAINGRCWTH

A numberoffactorsinfluencedobservedgrain-growthcharacteristicsintheexperimentalmaterials.Becausetheywerefairlycomplicated,considerationofthefollowingdiscussionof someof thesefactorswillhelpin understandingtheresultsofthestudies:

(1)Theexperimentalmaterialsintheas-receivedconditionhadbeenhot-workedtobarstockunderunknownconditions.In somecasesthegrainsizeswereinitiallymixed.Thegrain-growthcharacteristicswhenreheatedtonorml hot-workingorsolution-treatingtemperateindicatedsusceptibilitytoabnormalorunevengraingrowthinmostcases.usuallythistendencyvariedalongthebar-stocklengths.

(2)Thesevariedanduncertainprior-historyeffectswereminimizedinmostexperimentsby anequalizingtreatment.Thistreatmentwasafairlyheavyreductionby rollingcanbinedwitha heattreatmentfor1 hourat thenormalsolutiontemperature.Thisgavea uniformgrainstructureinmaterialwithuniformresponseto subsequentexperimentalvariables.Thecoo~ngratefromtheheattreatmenthadtobe restrictedto thatofair-coolingoroil-quenchingtoavoidsusceptibilitytoabnor-malgraingrowthon thesurfaceduringsubsequentreheating.

It shouldbe recognizedthattherearecertainImportantconsidera-tionsinvolvedin theseequalizingtreatments:

(a)Thebestwaytoavoidunevenorabnormalgraingrowthduringanysubsequentheatingisto introducemorethana minimumanountof uniformworkintothestock.As discussedlater,thisshouldbe a reductionlargerthanat least5 percent.Materialgivensuchreductionswould,however,be unsuitablefortheexperi-mentalprograbecausetheinitialreductionwouldmasktheexperi-mentalvariablestobe studied.

(b)Theequalizingtreatmentsdonotmakethematerialindepend-entofpriorhistory.Theactualgrainsizeisinfluencedby thepriorworkingandheatingconditions.Itcanbepostulatedthatifthepriorworkingresultsina materialwhichundergoesrecrystal.l.i-zationandgraingrowthto umiformreasonablyfinegrainsize,it isthenina conditionsuitableforstudyofabnormalgraingrowth.Therecrystallizationreducespriorstrain-hardeningtoa mindmum.As faras isknown,someothersequenceoftreatmentscouldhaveresultedina differentinitialgrainstructure.This,however,wouldaltertheresultsoftheexperimentsonlyin detail.

(c)First,theheat-treatmentstepprobablydidnotattaintheequilibrimngrainsizeforthetemperatureof.heating.Second,the

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degreeof solutionofexcessphaseswasprobablyvariable.Third,thecoolingfrcmitheheattreatmentintroduceda smallstraininthesurfaceofthemetal.However,by air-coolingoroil-quenchingthiswaskeptbelowthecriticalsmountrequiredforabnormalgraingrowth.

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(3)Theequalizedmaterialwhenreheatedforworkingmightormightnothaveundergonefurtheralterationofgrainstructureas a resultoftheadditionalheatingbeforeworkingactuaUystarted.

(4)Whenthetaperedspecimenswererolled,thefollowingr-e ofconditionswassetupinthespectins:

(a)A zoneofnoreductionwhere any change shouldhavebeenonlythatinducedby reheatixig.

(b)A zoneof increasingamountsofstrainresultingfromtheincreasingreduction.

(c)Ifthetemperatureofreductionwastcmlowforanyrecrys-tallizationfortherangeofreductions,thewholelengthofthespecimenwasstrain-hardened.Thiswasdependentonthesmountandtemperatureofreductionandtheopportunityforrecoveryduringcoaling.

(d)Ifthetemperatureofworkingwassufficientlyhighforrecrystallizationduringworking,therewasa zoneofincreasingstrain-hardeningfollowedby a zoneatthelargerreductionswherest~in-hardeninghadbeenreducedby therecrystallization.Ingeneral,thezoneofcold-workedmaterialdecreasedwithincreasing

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temperatureofreduction.Thezoneofrecrystallizationwasreducedin strain-hardeninginporportiontothedegreeofcompletenessofrecrystallization.W general,thisincreasedwithbothtemperatureandamountofreduction.

(e)Theair-coolingfromworkingintroducedsomesurfacestrainfromthethermalstresses.

(5) ~n the taperedwec~ns werereheatedfor solution trea~~t> .the reactionwascharacterizedby zonesasfollows:

(a)A zoneofno orverysmallreductionwherethegraingrowthwasmainlydependentonthefurther~owth tobe expectedfromunstrainedmaterial.Preswbly themachiningofthetaperedspeci-menremovedanysurfacemetalstrainedduringcoolingfromtheequalizingtreatment.Consequently,onlytheair-coolingfromtheworkingtemperaturewasinvolved.

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NACATN 4082 9

(b)A zonecoveringreductionsgenerallyintheorderof 0.4to5.0percentwhichwascriticallystrained,resultingina fewgrainsgrowingtoabnormalsizes.

(c)A zoneofhigherreductionswheredeformationresultedinmoregrainsgrowingincompetitiontopreventabnormalfinalgrainsize.

(d)A zoneofstilllargerreductionswhererecrystallizationdefinitelyoccurredin themoreseverelystrain-hardenedmetalduringreheatingunlessit occurredduringworking.Ihthelattercasegraingrowthoccurred.Manyof thespecimensshowedpa.rtialrecrys-tallizationat theheavierreductions.Presmablyrecrystallizationoccurredduringreheatinginthoselocationswhereit didnotoccurduringrolling.Thezonesofrecrystallizationpresmbly underwentgraingrowth.

Grain-growthdatawereobtainedforWaspaloyandInconelX-550alloys.Inaddition,dataarereportedforexperimentsonNimonic80Amaterialfromanotherinvestigation.Themajorexperimentalconditionsstudiedwereinductionofabnormalgraingrowthby repeatedheatingandcoolingandby deformationby rolling.

Intheexperimentsinvolvingrolling,taperedspecimenswererolledtoflatbars. Intheregionsof smallreductionscausingabnormalgraingrowth,as discussedinsubsequentsections,thegraingrowthwasremark-ablyuniformacrosstheentiresectionof thespecimens.TheHne ofdebarkationat thesmallestreductioncausingsuchgrowthwasverysharp.Therecrystallizationandgraingrowthwerealsouniformona macroscopicscaleacrossthebarsection.Recrystallizationduringworkingor aftersolutiontreatment,however,wasoftenbanded.

Air-andVacuum-MeltedWaspaloyAlloy

Grain-growthexperimentswerecarriedoutonbarstockfrombothair-andvacuum-meltedheatsofWaspaloyalloy.A numberofexperimentswerecarriedoutonthebarstocktoestablishgrain-growthcharacteris-ticsandto developinitialtreatmentswhichwouldprovidea reasonablyuniformandfineinitialgrainsize.

In theas-receivedcondition,theair-meltedstockwasfinegrainedontheoutsidewitha mixedgrainsizeinthecenter(fig.2). TMS

materialdevelopeda nonuniformgrainsizewhenheatedto1,9500F

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(fig. 3). Usingtemperatureshigherthm 1,950°F reducedthevariationingrainsizeanddidnotcauselargegrainstoform(fig.3). Itwas

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considered,however,thatitwouldbebesttoreducethebarstockfurtherby rollingbeforeheattreatmentinordertoobtaina uniform *finegrainsizewiththenormaltreatmentat1,950° F. A reductionof70percentfroml,9500F followedbya treatmentof1 hourat1,950°Fwasappliedtomaterialusedfortherepeatedheatingandcoolingexperiments.TTCLSgavea grainsizeof4 to6 (fig.3). A similargrainsizewasobtainedby a reductionof50percentfrom1,950°F (fig.4) andthistreatmentwasusedforallthedeformationexperimentsexceptwhenpriortreatmentwasdeliberatelyvaried.Figure4 showsthatrollingat1,950°F toa reductionof~0percentresultedinpartialrecrystalliza-tiontoveryfinegrains”.How&er,thismat&ialhadof4 to6 afterheating1 hourat 1,950°F (fig.4).

Thevacuum-meltedstockasoriginallyrolledhadto8 (fig.5). Heatingto1,950°F for1 hourgavea7 (fig.~). Thelatterconditionwasusedforallofexperiments.

a uniformgrainsize .-

a grainsizeof5grainsizeof4 tothegrain-growth

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InductionofabnormalgraingrowthbyrepeatedheatingandCOOli~.-Theexperimentsconductedtoinducegraingrowthbyrepeatedheatingandpoolingandtheresultinggrainsizesaresummarizedbyfigures6 to9.Theobservedgrain-growthcharacteristicswere:

(1)Air-coolingdidnotinduceabnormalgraingrowthinair-meltedstock.Therewasa gradualincreaseingrainsizeduringfourreheatssothatthefinalgrainsizewas2 to4 withfewrandomO grains(fig.6). -Vacuum-=ltedstockwasalsofreefromabnormalgraingrowthasa resultofrepeatedheatingandair-cooling.Thenormalgraingrowthwasless ●

thanfortheair-meltedstock,finalgrainsizebeing3 to 6 (fig.8).

Itshouldbenotedthatonek-hourcyclegavenearlythesamegrainsizesas fourcyclesofl-hourduration(figs.6 and8).

(2) Water-quenchingbetweenreheatsdidinduceabnormalgraingrowthstartingatthesurfaceinbothair-andvacuum-meltedstock.Theair-meltedstockdevelopedlargergrainsanda largerpercentageofabnormalgrains(figs.6 and8). Figures7 and9 shdwtypicalmicrostructureofthewater-quenchedstock.

Againitshouldbe notedthata h-hourreheatto1,950°F developedjustalmutasmuchabnormalgraingrowthasfourcyclesof1 houratl,950°F(fig.8).

(3)~r~elted ~teri~ initiallywater-quenchedfrom1,950°F butair-cooledduringfoursubsequentcyclesto1,950°F underwentnearly

NACATN4082 U

thesameabnormalgraingrowthasmaterialwater-quenchedduringeachcycle.Theinitialwaterquenchappearedtobethecriticalfactorcon-trollingabnormalgraingrowth(fig.6)

(4)Oil-quenchingdidnotinducesignificantabnormalgraingrowthinair-meltedstock.Thelargestgrainsfomedwereof sizeO (fig.6).

Theexperimentsindicatethat:

(1)Forthesizesandshapesstudied,air-coolingor oil-quenchingdidnotinduceabnormalgraingrowthduringsubsequentreheating.Water-quenchingdidinducea’unormalgraingrowthinbothair-andvacuun-meltedmaterialsdiningsubsequentreheating.

(2)Thegoverningfactorintheabnormalgraingrowthwastimeofheatingatthesolutiontemperatureandnotthenumberoftimesthemterialswerereheatedandquenched.Onewaterquenchwasjustaseffectiveasfouras longas thetotaltimeofheatingwasthesame.

(3)Thevacuum-meltedmaterialdidnotdevelopquitesolargegrainsas didtheair-meltedstock.

Inductionofabnormalgraingrowthby deformation.-Allof theexper-imentsoninductionofabnormalgraingrowthby defamationweredesignedtoestablishtheconditionswhichleadtoabnormalgraingrowthduringastandardfinalsolutiontreatmentof 4 hoursat 1,9500F. Therefore,allgrain-sizeratingsarebasedonmaterialwhichhadbeensolution-treatedaftersubjectiontovariousinitialtreat~ntspossiblyinfluencinggraingowth.

Themainresultwasthatgrainslsrgerthan1 wereinducedinmaterialwhichhadbeenreducedbetween0.4and5.0percent.A limitednumberofspecialconditionsresultedinabnormalgrainswhenreductionswereas smallas 0.1percentoras largeas 9.7percent.Intheselimitedcases,abnormalgraingrowthdidnotoccuroverthisentirerangeofreductionsbutratherdidoccuroversomensrrowreductionwithinthisrange.

Therewasa verysharpincreaseto grainsizesof -3to -4at thelowersideofthisrangeinreductions,usuallyforreductionsbetween0.4and1 percent.Thegrainsizethendiminishedsothatformostcaseswhenthereductionwas~ percent,themaximumgrainsizewas1 orless.

Thefollowingadditionalfeaturesof theresultscangeneralized:

(1)Therangeofreductionforabnormal-in growthoftemperatureofreduction.

aisobe

wasindependent

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(2)Vacuum-meltedstockunderwentabnormalgraingrowthafterthesmallcriticalreductionsinthesamemannerastheair-meltedstock.Themaximumgrainsizewas,however,lessforthevacuum-meltedmaterial,theusualdifferentialbeingabouttwosizessmallerforthevacuum-meltedmaterial.

(3) ~Orkingabovethe solution temperatureof1,950° F generallyreducedmaximumgrainsizeintheareaofabnormalgraingrowthinair-meltedstock.

(4)A nunberof conditionsofworkingandheattreatmentpriortocriticalreductionswerefoundtohavelittleeffectonthetendencyforabnormalgraingrowth.

(5) unifo~ reductionsmorethanthecriticalamountpriortoacriticalreductiondidnotcompletelysuppresstheabnormalgraingrowth.

(6) Utiformcriticalreductionina tensilemachinealsoinducedabnormalgraingrowth.

(7) A very steep Strain gradientfrm workingtendedtosuppressmaximumgrainsize,apparentlyby restrictingtheamountofmetalsubjecttoabnormalgraingrowth.

(8) A limitednumberofexperimentswerenotsuccessfulininducingabnormalgraingrowthasa resultofpartialrecrystallizationduringworking.

Thedetailsofthedatawhichledtothesesummarizedresultsarediscussedas follows:

Effectofmount andtemperatureofreduction:Abnormalgraingrowthwasinducedat somesmallreductioninallspecimensofair-meltedstockregardlessofthetemperatureofrolling(seetableI andfig.10). Thereductionsinducingthisgraingrowthwerebetween0.7and3.0percent.Themaximumgrainsizeinthisregionofreductionswas-3to -4except

forrollingat 2,000°and2,100°F whenitwas-2. Thegrainsizewaslessthan1 forallreductionslargerthan1.8to5 percentdependingontherollingtemperature.Typicalmicrostruc.turesforvariousreductionstakenalonga taperedspecimenareshowninfigure11.

Therollingtemperaturehadverylittleeffectonthatportionofthespecimenswhichwasnotreduced,exceptwhentherollingtemperaturewas800or2,100°F. Themaximumgrainsizesshownbyfigure10wereremarkablystiilarforreductionslargerthanthecriticalamountforalltemperaturesofrolling.Apparently,thevaryingdegreesofrecrystalli-zationduringrollingat1,8000to2,100°F didnotgreatlyalterthe

NACATN4082 13

? finalgrainsizefromthatinducedby strain-hardeningatlowertempera-turesofrolling.

H Vacuum-meltedstockrespondedsimilarly ta the air-meltedstock(tableIIandfig.12)exceptthatthemaximumgrainsizewas-2. Theoverallgrainsizewasalsofiner.Therealsowasno differenceinmaximumgrainsizein thecriticallyreducedsectionbetweenssmplesrolledat 2,100°F andthoserolledat lowertemperatures.Typicalmicrostructureofvacuum-meltedstockareshowninfigure13.

Itwillbe notedthatthechangein grainsizeinthecriticalsec-tionwasthesameforbothair-andvacuum-meltedmaterial.Althoughthissuggestschangeingrainsizeasa controllingfactoringraingrowthfromcriticalreduction,itwasnotborneoutby subsequentstudies.

Influenceofpriorhistoryonabnormalgraingrowth:A numberofdetailsin thetreatmentspriortorollingastaperedspecimenswerevaried.Themoreimportantresultswere:”

(1)Qnissionoftheheattreatmentat 1,9300F aftera reductionof50percentat 1,950°F didnotcompletelyeliminatethesusceptibilityToabnormalgraingrowthfromcriticalreductionalthoughitgreatlyreducedmaximumgrainsize(tableI andfig.14). Thiswastrueforspecimensrolledatbothroomtemperatureand1,6oooF. Theonlydif-ferenceforthetwocaseswastheratherhighreductionof6 to10per-

. centforabnormlgrowthwhenthespecimenwasrolledat1,600°F. Ithadbeenexpectedthattherewouldbe no tendencyforabnormalgrowthfromcriticalreductionafterthisheayyinitialreduction.

Theresultsoftheprecedingdiscussionshowthata reductionofmorethan~ percentatanytemperatureusuallyrestrictedthegrainsizetolessthan1. Itwaspresumedthatsuperimposinganyfurthersmuntofreductionwouldnotalterthetendencytoproducefinegrainsduringsolutiontreatment.Datapresentedlaterforspecimensstraineduni-formlyintensiontendto showthattheamountofdeformationandnotstraingradientsisthecontrollingfactorin criticaldefamationforabnormalgraingrowth.Thisthensuggeststhatthesuperimposingofastraingradientonmaterialstrainedpastthecriticalamountwasnotresponsibleforretentionof sanetendencyforabnormalgraingrowth.

Itis importanttorecognizeinconsideringthesepossibilitiesthat,aareduced50percentat 1,950°F, themetalwasnotsusceptibletoabnor-malgraingrowth.Itdoes,however,seemapparentthatfurtherreductionat somelowertemperaturecaninduceabnormalgraingrowth.ItiShighlyprobablethatthissusceptibilityarisesfrompartialsimultaneousrecrys-. tallizationleavingareasofessentiallystrain-freematerialwhichcansubsequentlybe criticallystrained.

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(2)Air-coolingfromthe1,950°F treatmentinsteadofoil-quenchingdidnotsubstantiallyalterthemaximumgraingrowthcausedby criticalreductionsat 800F (fig.14)or1,9000F (fig.15). Graingrowthwas,however,lessfortheair-cooledmaterialwhenitwasrolledat2,1OOOF(fig.15)forreasonswhichdonotseemexplainablefromtheavailableinformation.

(3)Itwasnotedthatthegraingrowthaftersolutiontreatmentwasconsiderablygreaterinthatpartofthetaperedspecimenswhichreceivednoreductionwhentherollingwascarriedoutatroomtemperature(figs.12and14). Apparently,the1/2hourofheatingforrollingat 1,400°F orhigherrestrictedgeneralgraingrowthduringthefinalsolutiontreatmentinmaterialwhichdidnotreceiveanyfurtherreduction.

(4)Theinclusionoromissionoftheequalizingheattreatmentat1,950°F beforerollingat 2,100°F hadpracticallynoeffectongraingrowth(seetableI andfig.16). Heatingfirstat 2,100°F andthendroppingthetemperatureto1,6oooF mayhaveincreasedtheamountofreductiontoinitiateabnormalgraingrowthfrom0.7to2.5percent.

Theseresultssuggestthatthetendencyforthecriticalreductiontoincreaseforrollingat2,100°F isduetoheatingto 2,100°F andnottoworkingat thattemperature.Thiswascarriedoverinthespecimencooledto.l,6~oF beforerolling.

(5) As-receivedmaterialreduced25percentat1,6000or 1,9500Fhadaboutthesamegrowthcharacteristicsformaxinmngrain size(fig.17) *asmaterialreduced50percentat 1,9500F whenallwereequalizedat1,950°F andoil-quenchedpriortorollingat 1,6000F. Thisresultissupportforthegeneralconclusionthatpriorhistoryhasrelativelylittle ‘effectonabnormalgraingrowthunlessthereisa largereductionwithoutopportunityforsubstantialrec~stallization.

Abnormalgraingrowthinducedby tensilestraining:Uniformcriticalreductionby limitedstrainingina tensilemachinewasusedtoobtainanindicationastotherelativeimportanceoftheamountofreductionandastraingradient.Specimenswerestretched:(1)1 percentat 1,400°F;(2)1 percentat 1,6oooF; and(3)2.5percefitat1,6000F. ThegrainsizesaftersubsequentsolutiontreatmentaregivenInfigure18.

Theresultsofthesetestsshow:

(1)Thel-percentelongationat1,400°F developeda maximumgrainsizeofonly-1.

(2)Thel-percentelongationat1,6000F gaveverynearlythesameresultas l-percentreductionbyrollingoftaperedspecimens,themaxi-mumgrainsizebeing-4.

NAcATN 4082 15

(3) A.11elongationof2.5percentat1,6000F strainedthe-e sec-tionmorethanthecriticalsmountsothatabnormalgraingrowthwasrestrictedto thefilletswherethestrainwasthesmallercriticalamount.

Thesedataareinterpretedto showthatthecriticalstrainis thecontrollingfactorandnotthestraingradient.Theabsenceofappre-ciablegraingrowthafterstraining1 percentat 1,4000F apparentlywasduetothestrainbeingbelowtheminimumsmountrequired.

Influenceofrecrystallizationduringworking:Theapparentconfine-mentofinductionofabnormalgraingrowthtoa smallcriticalreductionraisedquestionsastowhetherthesameconditioncouldbe attainedbypartialrecrystallizationduringworking.Sincerecrystallizationleavesa relativelystrain-freecondition,theremustbe straingradientsbetweentherecrystallizedandtheUnrecrystallizedzones.

Themethodofstudyselectedwastorolltaperedspecimenssoas toobtainreductionsfromO toabout29percent.Thiswouldprovidea widerrangeofrecrystallizationthanwasobtainedinthebarsreduceda maximumof15percent.T&nperaturesof1,8500,1,950°,and2,0500F wereusedtovaryfurthertherecrystallizationcharacteristicsduringrolling.Thegrainsizesobtained(tableI andfig.19)alongwithtypicalmicrostruc-ture (fig.20)indicatethefollowingthings:

(1)Thereductionforabnormalgraingrowthremainedapproximatelythesameas thatwhichhadpreciouslybeenfound,0.4to 5.8percent.Themaximumgrainsize,however,was-1to -2insteadof -3to ~. Thenarrowerzoneof criticalreductioninthebarswiththegreatertaperapparentlyrestrictedthemaximumgrainsize. Thisseemedtobe duetoan insufficientvolumeofmetalbeingcriticallydeformedtoprovideenoughmaterialforlargergrains.

(2)No abnormalgrtinswerefoundin theregionsreducedmorethanthecriticalsmountinspiteofa widerangein degreeofrecrystallizat-ion duringrolling.

(3) me mterial reducedmorethan10percentat 1,8500F didshowgrainshavinga sizeof1 to 2 inbandsbetweenfinergrainedareas(fig.20(C)).Thisappearedtobe duetograin-boundarymigrationfromthefewverysmallrecrystallizedgrainswhichformedduringrol~ng.Theseapparentlygrewpreferentiallyat theexpenseof surroundinggrains.

(4)Thematerialreducedover7 percentat 1,950°F underwentexten-sivepartialsimultaneousrecrystallization(figs.20(d),20(e),20(f),and22). However,uponsubsequentfinal.solutiontreatment,a uniform

16 NACATN4082

fine-grainedstructurewasobtainedintheregionsofthetaperedspeci- rmenwhichreceivedtheheavierreductions(figs.20(d),20(e),and20(f)).

Thesespecimensweresolution-treatedat 1,975°F inaccordancewith \morerecentcommercialpractice.Thereisno reasontobelievethatthisincreasefrcm1,950°F appreciablyaffectedtheabno~l-grain-growthcharacteristics.

Theinvestigationofthepossibleinductionofabnoml graingrowththroughpartialrecrystallizationwastoolimitedtoallowdefinitecon-clusions.Theresults,however,pointtocertainprobablefundamentalswhichsuggestthatitwouldbe verydifficulttoinduceabnormalgraingrowthinthismanner.Anystraingradientsbetweenrecrystallizedsmdunrecrystallizedareaswouldbeverysteep.As discussedintheprevioussection,thiswouldprobablylimitthemaximumgrainsizebecauseofthesmallamountofavailablemetalsubjecttoabnormalgraingrowth.Inaddition,thereisgoodreasontobelievethattheUnrecrystallizedgrainsa~acenttorecrystallizedgrainsme deformedmorethanthecriticalamountforabnormalgraingrowth.Thiswouldresultina verynarrowzoneoreventheabsenceof criticaldeformationwithlittleorno tendencyforabnormalgraingrowth.

Influenceofrateofheatingonabnormalgraingrowth:Theoccur-renceofgrainswitha sizeof1 to2 inthesamplerolledat1,85cPF toreductionsof10to20percent,as describedintheprecedingsection,suggestedthepossibilityofabnormalgraingrowthfroma fewsmallsimul-taneouslyrecrystallizedgrains(figs.20(a),20(b),and20(c)).E a slow -rateofheatingwasused,thefewverysmallgrainswhichformedduringrollingat 1,8500F (figs.20(a)and20(b))mighthavean opportunitytogrowevenlarger.Verylargegrainscanbegrowninmetalswhenonlya ?fewsmallgrainsformbyrecrystallizationandaregiventimeenoughtogrowata relativelylowtemperaturetolargegrainsattheexpenseofthesurroundingstrainedmetal.

Accordingly,a samplewaspreparedandtaper-rolledtoincludeaconsiderableregionofreductionbetween10and20percent.Whenitwasheatedfroml,40@to1,950° F in3 hours,thegrainsizesfound(tableIandfig.19) wereno Ufferentfromthosefoundwhenitwasplacedinafurnaceatthemaximumtemperature.

As farascouldbeascertained,theslowrateofheatinghadlittleeffectontheabnormalgraingrowthatthecriticallydeformedsection.Itcertainlydidnotincreasegrainsizeinthisarea.

Itwillbenoted,however,thatthecriticalreductionforabnormalgraingrowthwasonly0.1percent.Thislowvaluesuggeststhatthecriticalreductionforabnormalgraingrowthis sensitivetoheatingrate. *

JRNACAm 4082

If so,unrecognizedvariationsinheatingratetheapparentlyunexplainablevariationsinthe

17

couldaccountforsomeofminimumreductionfor

abnorn&lgraingrowthobservedthroughouttheinvestigation.

Degreeofrecrystallizationduringworking:Duringtheinvestiga-tion,esthatesweremadeoftheamdnt ofrecrystallizationinas-rolledstructures.Thesearesmmarizedinfigure21. Forsanereason,thelargerA very

A

reductionsgavemorerecrystallizationat l,95@ thanat 2,050°F.smallamountoccurredat1,8500F andnone

InconelX-550Alloy

numberofheattreatmentswerecarriedout

at lowertemperatures.

on theas-receivedInconelX-’55Obarstocktoestablishinitialgrain-growthcharacteristics.Itwassubjectto unevengraingrowthat l,90@and2,0@ F andtoabnormalgraingrowthat 2,100°F (seefig.22). Thetendencyforabnormalgraingrowthwasreducedat 2,20CPF. ~ical microstructureareshowninfigure23.

Inductionofabnormalgraingrowthby repeatedheatiwandCOOli~.-!l%eInconelX-550stockwasreduced64 percentfrom2,15@F andthen-heatedas showninfigure24. Fourandfivecyclesto 2,1’5@Fwithair-coolingdidinduceSOK abnormalgraingrowth.Thisgrowthoccurredduringthefirstreheatafteran initialwaterquenchandbecamemoreextensiveduringsucceedingcycles(fig.25).

TheInconelX-550materialwasquitesensitivetoabnormalgraingrowthfromthesurfaceifwater-quenchedandreheatedto2,150°F. Itwasfarlesssensitivewhenair-cooled.However,repeatedair-coolingor,moreprobably,increasedheatingtimeat 2,15@F resultedin someabnormalgraingrowth.This,togetherwiththee~rimentscarriedoutontheas-receivedstock,indicatesthatabnormalgraingrowthcanoccurin 1 to4 hoursofheatingat temperaturesabove2,00@ endbelow2,2000Fforeitherair-cooledorwater-quenchedmaterial.

ApparentlyInconelX-550wasscmewhatmoresusceptibletoabnormalgraingrowthfrcmrepeatedheatingandcoolingthanWaspaloy.At least,abnormalgraingrowthwasnotinducedinthelattermterialby repeatedair-coolingfromitssolutiontemperature.

InductionofabnormalgraingrowthinInconelX-550alloyby deforma-tion.- As-receivedIncopelX-550stockwasheatedfor2 hoursat l,90@ F,-cooled, andmachinedintotaperedspectienshatinga uniformgrainsizeof7 to 8. Abnormalgraingrowthoccurredduringfinalsolutiontreatmentat 2,15CPF inregionsreduced2.6to10.5percentduringrol~ngat1,6000,1,8000,and2,000°F (table=Iandftg. 26(a)).Therewasno abnormalgraingrowthtiterrollingat 2,200°F. Increasingthetemperatureofrollingfrczu1,8000to2,000°F reducedtherange

18 NACATN4082

ofreductionssubjecttograingrowth.Itwillalsobenotedthattherewasno tendencyforabnormalgraingrowthinthesectionofthespecimenswhichreceivedno.reduction.Evidentlytheheattreatmentat1,9000F ortheremovalof surfacemetalinmachiningthespecimenseliminatedthesusceptibilitytoabnormalgraingrowthat 2,1500F originallypresentinthestock.

Taperedspecimenswerepreparedfromstocksolution-treated2 hoursat 2,1ONF. Themachiningremovedthesurfacenmterialwhichunderwentabnormalgraingrowthduringtreatmentat 2,1M1°F andleftmaterialwitha uniformgrainsizeofO to5.

ThecriticalreductionforabnormalgraingrowthintheInconelX-550materialwasbetween0.4and1.4percent.Again,rollingat2,20@Fpracticallyeliminatedabnormalgraingrowth.Thetendencywasalsoslightlyreducedby rollingat 2,~OoF incomparisonwithrollingat1,6oooor1,80@F (fig.26(b)).

Somestockwasreduced50percentat 1,950°F andthenmachinedintotaperedspecimens.Whenheatedto2,1OWF for0.5hourandrolled,itwassub~ecttoabnormalgraingrowthfora reductionof4 to7.8percent(fig.26(c)).Figure27showstypicalmicrostructureofthesespecimens.~n thespecimenwascooledto 1,6000F beforerolling,therangeofreductionforabnormalgraingrowthwassomewhathigher.Thislattermaterialalsodevelopedgrainsas largeas -1whenreductionwasverysmall.

Apparentlytherecrystallizationduringworkingatl,95@F plus.

thatonheatingto2,100°F changedtheamountofreductionforcriticalgraingrowth.Possiblyrecrystallizationandgraingrowthduring .heatingat 2,1000F forrollingleftlessresidualstrainfrompriorhistoryandthereforerequiredmoredeformationtoinducecriticalstrain.Possiblygrain-sizedifferenceswereinvolvedinthechsmgeincriticaldeformation.

Theas-receivedNimonic80Astockhada grainsizeof6 to 8. Fig-ure28 showstheinfluenceofvariousheatingconditionsongraingrowthin thismaterial.Heatingfor4 hoursat1,950°F developeda grainsizeof1 to 3. Highertempemturesresultedinlargergrains,includingabnormalgrains.

Experimentsinvolvingvariousconditionsofroll~.- Experimentswerecarriedoutinvolvingvariousconditionsofrolling.E?athas-receivedstockandstockreduced50percentat L,950°F followedby al-hourtreatmentat1,950°F wereutilized.Theoriginalgrainstiucture

.-

.

NACATN4082

forbothmaterialsis shownby figure29. Itwillbementof1 hourat 1,950°F resultedina structureofwithbandsofveryfinegrains.

19

notedthata treat-fairlycoarsegrains

Inductionofabnormalgraingrowthby deformation.-IngeneraltheNi.mcmic80Astockunderwentabnormalgraingrowthinthesamemannerastheotheralloys.Oneoutstandingdifferencewasthetendencyforgrainsizesof1 to O to developafterlargereductions.

Effectoftemperatureandamountofreduction:Materialwhichhadbeenreduced70percentat 1,950°F andthenreheatedfor1 hourat1,950°F andair-cooledandpreparedas taperedspecimensandrolledat1,750°,1,8500,and1,950°F andreheatedundertheconditionsoutlinedintableIVandfigure30. Abnonuslgraingrowthto sizesgreaterthanOtookplaceforreductionsbetween0.1tid8.5percentwhenthespecimenswerereheatedby beingplacedina furnaceat 1,975°F. Thelsrgergrainsizewasneversmallerthan3 andusuallywas1 or O forthelargerreduc-tions. Sofaras theeffectoftemperatureofreductionwasconcerned,therewereonlyminorvariationsofdoubtfulsignificanceinthemaximumsizeof thegrainsformedby abnomalgrowth.

Reworkingafterpriordeformation:A specimenequalizedby a50-percentreductional1,9500F followedbya l-hourtreatmentat 1,950°Fwasrolledonceasa taperedspecimen,reheatedto 1,9500F for10minutes,andagainpassedthroughtherolls.E!.ecauseof springbackof therollsthesecondpassimposedaboutl-percentadditionalreductiononthespeci-men. TheobservedgrainsizesafterfinalsolutiontreatmentaregivenintableIVandfigure30. Itisimportantto recognizethatthereductionsshownarethecombinedreductionfromthetwopasses.Theobservedgrainsizesareinterpretedas follows:

(1)Duringthe10-minutereheatto1,9500F, considerablereliefofstrainfromtheoriginalreductiontookplace.At smalltotalreductions,thecombinedeffectoftherelativelysmallfurtherreductionfromthesecondpassandtheinitialreductiondidnotbecomeeffectiveforabnormalgraingrowthuntil”thepointwherethetotalreductionwas1.6 percent.

(2)Foralltotalreductionsbetweenabout8 percentandabout23per-cent,thestrainrelieffromthe10-minutereheatwasprobablyinsufficienttobringtheresidualstrainbelowthecriticalamount.Therefore,thesecondpassdidnotinduceabnormalgraingrowth.

(3) For tot- reductions be~een 23 and28 percent, extensiverecrys-tallizationoccurredduringtheoriginalpass. Thisrecrystallizationprobablyleftthematerialessentiallystrainfree.Whengiventhesecondpassitprobablywasthencriticallydeformedandbecmnesusceptibletotheobservedabnormalgraingrowth.

20 NACATN4052

Anotherspecimenwithlesstaperwasmadefromas-receivedstockandsubjectedtothesamesequenceofoperations(seetableIVandfig.31). Thebehaviorwasverysimilartothatof thepreviouslydis-cussedspecimenoverthecomparablerangeoftotal.reductions.Thissecondspecimendiddevelcrpconsiderablycoarsergrainsintheregionswheretherewasmorethana criticalreductionthana similarspecimengivenonlyonepass. Thegrainsizein thisregionwassimilarto thatof thefirstrerolledspecimendiscussed.Infact,itwassimilartothatof allthespecimensfirstequalizedat 1,950°F. Thissuggeststhatthecomuonfactoroftwobeatingstol,95@F wasresponsiblefortherelativelylargegrainsizefora morethancriticalreduction.

,#–

Themostimportantfeaturesof theresultsof theseexperimentsare:

(1)Evidenceofconsiderablestrainreliefin10minutesat 1,950°Fwithouta cooltoroomtemperature

(2)Furtherindicationthatextensiverecrystallizationduringworkingleavesalloyssusceptibletoabnormalgraingrowthfromsmalladditionaldeformation

(3)Evidencethatrepeatedheatingtotonearabnormallylargesizesfor

Froma practicalviewpoint,thechangesinsmalltobe significant.

.-

1,95(YF increasesgrainsizemetalnotcriticallyreduced

criticalreductionweretoo

.

Effectofheatingrateonabnormalgraingrowth:Reducingtheheatingrateto solutiontemperatureafterrollingat 1,85@F (fig.30)practicallyeliminatedabnormalgraingrowthandrestrictedgrainsizeforlargerreductions.Bringingthespecimenup slowlyinthefurnacefrom1,400°to1,950°F in comparisonwithplacingthespecimeninafurnaceat 1,950°F couldbe expectedtogiveconsiderablestrainreliefbeforethetemperaturewashighenoughforgraingrowth.Theopportunityforprecipitationandagglomerationat thelowertemperaturesmayalsohaveincreasedgrain-growthrestrainers.Bothfactorswouldfavortheobservedreductioningraingrowth.

Slow-heatingmaterialfrom1,950°to2,300°F afterreductionatl,95@ F increasedgrainsizeforsllreductions(fig.32)whencomparedwithmaterialrapidlyheatedto2,300°F. Inthiscase,graingrowthcouldoccuratalltemperaturesinvolvedandtheincreasedgrainsizewasprobablydueto in~reased

Influenceof temperature1,950°F: Severalconditionstaperedspecimensat 1,950°Ffig.32):

timein thegrain-growthrange.

ofsolutiontreatmentafterreductionatofheatingwereusedafterreductionofwiththefollowingresults(tableIVand

.

NACATN 4082 21

.

m

(1) One hourat 2,100° F gavethesanecriticalgraingrowthas4 hoursat 1,950°F. Themaindifferencewasthelargergrainsizeforthelargerreductionswiththe2,100°F treatment(grainsizeof O ascomparedwith3 (fig.31)).

(2)Onehourat 2,2W F gavea maximumgrainsizeof -1. Themaximumgrainsizevariedbetween-1andO alongthelengthofthebar.Apparentlysolution-treatingat 2,200°F erasedanyeffectof criticalreduction.

(3) me how at 2,250° J?wasvery similarexcept that a grainsizeof -3developedfor1.6-percentreduction.

(4)Onehourat2,300°F wassimilarto1 hourat 2,250°F exceptthatthegrainsizesalongthebarvariedbetween-1and-2.

Themostimpor-t featureoftheseresultswastherelativelylittleeffectofextremelyhightemperaturetreatmentson abnormalgraingrowth.Inadvertenthightemperaturesapparentlyarenot a majorfactorinabnormalgraingrowthprotidedit canoccurat nomal heatingtemperatures.Theabsenceofabnormalgraingrowthinheatingat 2,200°F suggeststhatthereareintermediateconditionsof strainrelief,solutionofgrain-growthrestrainers,andgrain-growthcharacteristicswhichrestrictabnormalgraingrowth.

DISCUSSION

Theinvestigationprovidesconsiderableinformationregardingtheconditionswhichcancauseabnormalgraingrowthinheat-resistantalJoysofthetypesstudied.Many,ifnotmost,oftheconditionsofworkingtobe avoidedforfreedcmfromabnormalgraingrowthcsmbe specified.Thebasicmechanismsinvolvedinmanyoftheinterrelatedvariablescanalsobepostulatedfromthetheoryof graingrowth.

PreventionofAbnormalGrainGrowth

Allof theresultsindicatethatsmallamountsof deformationappliedtoessentiallystrain-freemetalareresponsibleforthedevelopmentofabnormalgraingrowth.Whensuchcriticallystrainedmtal isreheatedtotheusualhot-workingor solution-treatingtemperatures,abnormalgraingrowthmayoccur.Themainprobleminpreventingabnormalgraingrowthseemstobe theanticipationandavoidanceoftheoftenccxnplexconditionswhichcaninducecriticalstrain.Theusualtemperaturesandtimeperiodsof solutiontreatmentaresufficientforabnormalgraingrowth.Eeating

22 NACATN4052

conditionsforhot-workingmy ormaynotdevelopabnoxmalgrainsdependingonthetemperaturesandtimeperiodsused.

Theamountof strainrequiredtoinducesusceptibilitytoabnormalgraingrowthwasrathersmall.Inmostcasesstudied,itwasa smallportionof thereductionintherangebetween0.4and7.0percent.Overalltheexperimentsthisreductionwasaslowas 0.1percentandas highas 9.7 percent.Thismeansthat,if themetalisreducedat least10per-centinallpartsduringanyoneworkingoperation,itshouldbe freefromabnormalgraingrowth;inmostcasesa reductionof7 percentisadequate.Theonlyexceptiontothisrulenotedwasthecasewherea smallreductionwasappliedafterfairlylargeemountsofreductioncausedrecrystalliza-tionduringworking.Therecrystallizationleftthematerialessentiallystrainfreeandthesmallamountoffurtherstraininginducedsusceptibil-ity. Thisapparentlydoesnotoccurwhenreductioniscontinuedat essen-tiallyconstanttemperatureafterrecrystallizationstartsifthelastpassisheavy.A reheataftersuchrecrystallizationfollowedbya smallcriticalreductiondefinitelyinducessusceptibility.Continuedreductionwitha fallingtemperatureafterrecrystallizationathighertemperaturesisa lessobviousbutimportantsourceofcriticalreduction.

Thedataclearlyshowedthatsusceptibilitycanbereducedbyrapidcoolingfrcma hightemperature.Inthiscase,thethermalstressescriticalJ_ydeformthesurfaceofthestock.Itshouldbe clearlyrecog-nizedthatthisisa casewherethedimensionsofthemetalpiecetogetherwiththecoolingratearecombinedvariablesgoverningtheamountofthermallyinducedstrain.Air-coolingcaninduceabno?mmlgrowthin some .cases.Inothershapes,water-quenchingmaybe required.Iftemperaturegradientsortherestrainttocontractionissufficientlysmallevenwater-quenchingwillnotcriticallystrainthemetal.Thissourceof .criticalstrainisfavoredbyhighthermalexpansionandlowthermalcon-ductivity.Itshouldbenotedthatcoolingrateaftera reductionlargerthanthecriticalamountwillhavenoeffecttecausethethermallyinducedstrainwillbemerelysuperimposedonthestrainalreadypresent.

Theseresultsclearlyindicatethefoil.uwingprinciplesnecessarytoavoidabnormalgraingrowth:

(1)Rapidcoolingfromanessentiallystrain-freeconditionmustbeavoided.Thus,ifmetalisheatedunderconditionswhichremovestrainfrompriorworkingandthencooledrapidlyenoughtodeformthesurfacecriticallyby thermalstressing,itwillundergoabnormalgraingrowthwhenreheatedto usualsolutionorhot-workingtemperatures.Thiscondi-tioncouldprobablybeencounteredoncoolingfromhot-workingonlyifthereductionconditionsweresuchthatrecrystallizationtoanessentiallystrain-freeconditionoccurredduringtheworkingoperation.Likewise,anysectionofa partwhichreceivednoreductionwouldbe susceptibleafter

.

suchCOOlillg.--

.

NACATN4082 23

(2)Thecriticalreductionfordevelopingsensitivitytoabnormalgraingrowthisessentiallyindependentof temperatureofstraining.Thus,ifmetalisannealedandcold-straightenedbymethodswhichfntro-ducesmallstrains,thosesectionsof themetalreceivingcriticaldefor-mationswillbe susceptible.

(3) Anyreduction shouldbe morethanthecriticalmount. !rhusareheatfollowedby a smallfinishingreductionshouldbeavoidedif thereheatconditionsleavethemetalessentiallyfreefromstrainfrompriorreduction.

(4)Inhot-workingindies,it isessentialthatthedeformationinallpartsofthepiecebemorethanthecriticalanmunt.Thismeansthatthediesmustbe designedtoinsuremorethanthecriticalamountofmetalmovementineverystep. Cammonsourcesof difficultyincludedie“hangup”wherethemetaldoesnotmove,incorrectproportioningof thesequencyof diesso thatsomepartsofthepiecereceivelittleornoreductionin somesteps,andflashpreventingdiesframclosingtherebyrestrictingmetalflowto smallamountsinsomeparts.Tkimingofflashfroma forgingaftera reheatwithoutanyotherreductionisa commonsourceof criticalreductionifthereheatreld.evespriorstrainbecausetheoperationintroducesa straingradientcertaintoincludecriticaldeformation.

(5)Abnormalgraingrowthcanoccurduringreheatsif thetimeandtemperatureofreheatingme sufficientforthegraingrowth.Eventhoughinitialreductionsmaybe largerthanthecriticalreduction,it canoccurduringsubsequentreductionsifreheatingrelievespriorstrain.Repeatedstepsinvoltingcriticalstrainandgrain.growthduringreheatsarealmostcertainlythecauseofextremelylargegrainssometimesencounteredinforgingturbineblades.‘Therepeatedsequencecausesadditionalgrowthduringeachreheat.

(6) Thepossibilityofrecrystallizationduringworkingrenderingmetalsusceptibletoabnormalgraingrowthfroman additionalsmallreductionseemstobe a fairlyimportantprinciple.Thisrecrystalliza-tionisprobablya comon sourceoffairlylsrgegrains(grsAnsizesoftheorderof O to -1. Itprobablyexplainswhymanysuccessfulforgingoperationsforgas-turbinebladesrequiretheMmitingoftheforgingblowstooneperheat. Thefirstblowata relativelyhightemperatureinducesrecrystallizationwithlittleorno strain-hardening.Thetemperaturefallsrapidlyandadditionalblowsprobablyresultinsmalldeformationswhichcriticallydeformtherelativelystrainfreemetal.Ifmultipleoperationsperheataretobe used,caremustbe exercisedtobe surethatrecrystallizationisnotfollowedbysmallcritical

. reductionsat a lowertemperaturewhererec~stallizationstops.

.

24 NACATN4082

(7) Forging experienceindicates that temperatureandtimeof A

heatingandthecapacityofhot-workingequipmentareimportantpracticalvariables.Thereasonforthisapparentlyinvolvesseveralfactors.Themostimportantfactorprobablyistheuniformityofmetalflowina Me .

as influencedby thetemperature-sensitiveflowcharacteristicsofthemetal.Timeofheatingprobablygovernsamountofrelieffrompriorstrainandgrain-growtheffectsduringreheats.Smallpartsandthinedgescoolrapidlyina dieandmaybecomesoresistanttodeformation —

thatthedeformationpossiblewiththeequipmsntbeingusedis limitedto thecriticalamount.

(8) Inadvertentabnormallyhightemperaturesofheatingforhot-workingorsolutiontreatmentappeartobe a relativelyunimportantfeatureofabnormalgraingrowth.Thema~orexceptiontothisappearstobe thecasewherethenormalhot-workingor solutiontemperaturesandtimesweretoolowforabnormalgraingrowthtooccur.Inthesecases,an abnormallyhightemperaturewillpermitabnormalgraingrowthaftercriticaldeformationwhentherewouldbeno evidenceofitfromnormalheatingconditions.Thesizeofabnormalgrainsincreasesonlyslightlywithtemperature.Ifabnomalgraingrowthcanoccurduringnormalheating,theincreasefromabnormallyhightemperaturesisrelativelysmall.

(9) Thesegeneralities are restricted totheformationofabnormallylargegrainsunderconditionswhichnormallydonotdevelopexcessivelylargegrains.Theinvesti~tiondidnotconsiderthecausesofmixedgrainsizeswherethelargestgrainsareoftheorderof1 orO. Several ninstancesofthistypeofgraingrowthwere,however,notedintheexperi-ments.Thedevelopmentofa veryfewrecrystallizedsmallgrainsduringworkingata relativelylowtemperaturewasonesource.

.Partialrecrys-

tallizationcaustngbandsofstrainedandrecrystallizedsmallgrainswasanother.In somecases,certainconditionsofpriorheatingcausedrelativelylargegrainstoformduringa subsequentreheat.Excessivelyhightemperaturesofheatingfrequentlycauseduniformlycoarsegrainstoform.

(10)Theinvestigationshowedthatthedegreeofreductionandnotstraingradientswasthemajorcauseofabnormalgraingrowth.Abnomalgraingrowthisusuallyassociatedwithstraingradientsonlybecausethecriticaldefo-tionisusuallypresentinthegradient.Thecritical-deformationrangeissosmallthatitcaneasilybemissedinuniformreduction.

(11)Workingat or slightlyabovethenormslsolutiontemperaturecannotbe dependedontoreduceabnormalgraingrowth. —.

.

.

.

mm m 4082 25

MetallurgicalandCompositionalEffects

Theinfluenceofmetallurgicalvariablesandcompositionaleffectsonabnormalgraingrowthwasnotstudiedin detail.However,certainobservationsanddeductionscanbemadefromtheexperimentalresults:

(1)Thevacuum-meltedWaspaloyalloydidnotdevelopabnormalgrainssolargeas didtheair-meltedstockandtendedtobe generallyfinergrained.fitheory,thevacuum-meltedmaterialshouldhavefeweroxides,nitrides,andotherdispersedphaseswhichactas grain-grawthrestrainersthantheair-meltedstock.Ifthiswerethegoverningfactor,thetemper-aturesandheatingtimeforgraingrowthoughttobe reduced.This,therefore,canhardlyaccountfortherestrictionof theabnormalgraingrowth.Thevacuum-mltedheathada carboncontentof 0.08percentwhiletheair-meltedheathadonly0.03percentcarbon.Thisisa sufficientdifferencesothatthelargersmountof carbidesinthevacum-meltedmaterialshouldrestrictgraingrowthappreciablymorethanthosein thelowercarbonair-meltedmaterial.Whilethisinvestigationdidnotdemonstratethatthecarboncontentwasthecontrollingfactorbetweentheair-andvacuum-meltedstock,italonecouldbe responsiblefortheobserveddifferences.

(2)Thecompositionofthealloyswasrelatedtothetemperaturesandtimeforabnormalgraingrowth.Forthethreealloysconsidered,Nimonic80Ahadtheleastresistancetograingrowth.Itunderwentrapidgraingrowthat 1,950°F. Waspaloyrequiredconsiderabletimeforabnormalgraingrowthat 1,9500F. InconelX-570requireda temperatureabove2,000°F andstillrequiredsometimeat 2,1500F forabnormalgraingrowth.

ThecomparativelyhighcoarseningtemperatureforInconelX-570alloywasprobablyduetothegrain-growth-restrainingeffectof columbiumcom-pounds. ThemaindifferencebetweentheNimonic80AaudtheWaspaloyalloyspresumablywasthehighertitaniumandahmrhnmcontentsofthelattermaterial.Thispresmablyincreasedresistancetograingrowth.

(3)mere weremanyaspectsof thedetailsof theobservedgrain-growthvariationswhichseemtobe dueto differencesin grain-growthrestraintfromdispersedphases.Theusualsolutiontemperaturesappa-rentlyareonthelowersideof thetemperaturerangeforsolutionofsuchphases.Thegraingrowthwasrelativelyslowat thetemperaturesused. Undersuchconditionsthecriticaldeformationcouldbe expectedtobe sensitiveto theconditionsof thegrain-growthrestrainersandpos-siblytothesizeoftheabnormalgrains.Thisfactseemedtobe involvedintherestraintofgraingrowthbypriorheatingintheprecipitate-agglomerationrangeofl,kOOOto1,700° F. Itprobablywasa factorin

.

26 NACATN4082

thevariableeffectonabnormalgraingrowthduetoworkingat orabovetheusualsolutiontemperature.

(4)Deformationofmultigrainedmaterialsisnotuniformonamicroscopicscaleeventhoughitmaybe ona macroscopicscale.Themicroscopicflowcharacteristicsprobably-y dependingonthetemper-atureandmethodofworking.Consequently,itcouldbe expectedthattherathernarrowrangeofreductionsinducingabnormalgraingrowthcouldbe sensitivetodetailsofthemechanismsofflowduringworking.Furthermore,suchmetallurgicalfactorsas compositionaldifferencesgrainsize,dispersedphases,anddegreeofsolutionofdispersedphasesco@d influencefluwcharacteristicsandtherebyinfluencecriticaldeformationdetails.

—

(5) TheSize d grainsandextentofabnormalgraingrowthwereremarkablyinsensitivetoincreasedtemperaturesofheatingabovethelowesttemperatureatwhichabnormalgraingrowthwouldoccur.Therewere,however,certainintermediatehighertemperatureswhichinsomecasesrestrictedabnormalgraingrowth.Theexplanationoftheseeffectsisnotclearfromthisinvestigation.Thereareprobablyseveralinterrelatedeffects.Increasedtemperatureshouldintensifygraingrowth.Ontheotherhand,verylargegrainsrequireinitiationofgrowthfromonlya fewcenters.Increasingthetemperaturewouldincreasethenum-berof centersofgraingrowthandtherebyrestrictgraingrowththrough- - _competitionforsurroundinggrains.An increaseintemperaturewouldalsotendtoreducegrain-growthrestrainersby solutionandtherebyincreasethecentersnucleatedforgrowth.Somestrainreliefprobablyoccurs bduringheatingbeforegraingrowthstarts,therebyinfluencingcriticalstrain.Thiscouldbeexpectedtobevariabledependingontemperatureandheatingrate. Possiblythiswouldresultinvariationintheamount

.

ofinitialstrainrequiredtoleavea residualcriticalstrainat thetimethemetalattaineda temperaturesufficientforabnormalgraingrowth.

Strainreliefduringheatingtothehighertemperaturesofrollingmaywellbe thecauseforthegeneralincreaseintheamountofstrainrequiredforcriticalgraingr~h.

(6) Ingeneralitappearedthatabnotilgraingrowthwasfairlyindependentof initialgrainsize. Inthosecaseswheretherewasanapparentgrain-sizeeffect,it isprobablethatvariationingrain-growthrestrainerswasthecontrollingfactor.

(7) There-S considerablevariationintheamountof deformationrequiredto initiateabnomnalgraingrowth._me reasonswerenotclear.Varyingstrainsfromcoolingwereprobablya factor.Also,aspreviously ‘d-iscussed,variationingrain-growthrestrainerscouldhavebeeninvolved.

.

NACATN 4032 2’-7

.

“

.

b

Therewasalsosom etidencethattheamountof deformationwasrelatedtorateofheatingtothesolutiontemperature.Themostimportanteffect,however,wasprobablyunrecognizedvariationsin thestrainfromtheconditionsofmanipulationusedintheexperiments.

MechanismofAbnofilGrainGrowth

Therearetwobasicmechanismsresultingin graingrowth:(1)Absorp-tionof surroundinggrainsby grain-boundarymigxation,and(2)formationofnewgrainsby recrystal~zationfollowedbygrain-boundarymigration.Eathmechanismsrequirea differenceinenergybetweengrainssuchthatthoseat a higherenergylevelareabsorbedby thoseat a lowerenergylevel.Inthefirstcase,somefactorsetsupa conditionsuchthatscmegrainsareat a higherenergylevelthanothers.Itisthecommonmecha-nismforgrowthoflargergrainsfrcnnsmallergrains.Inthesecondcase,reliefof straindueto deformationcausesa smallnewgraintoform.Thisgrainthengrowsat theexpenseofthesurroundingmetalwhichis ata higherener&ylevelby virtueofthestrainpresent.Iftherearemanycentersatwhichthesmallnewgrainsforminrelationtotheoriginalgrainsize,therewillbemoregrainsafterrecrystallizationis completeandgrainrefinementwillhaveoccurred.Iftherearefewcentersstrainedenoughtorecrystallize,growthof onlya fewgrainswilloccurresultingingraincoarsening.

Theliterature(refs.“3snd4) doesnotclesrlydefinewhetherabnormalgraingrowthoccursby grain-boundarymigrationofexistinggrainsorby growthofa veryfewsmallgrainsformedby recrystalliza-tion. Ineithercasetheessentialfeaturewouldseemtobe nonuni-fotityofstrainwithintheindividualoriginal~ains. Grain-boundsrymigrationwouldrequirethata fewgrainsreceiveverylittlestraininrelationtotheirneighboringgains. Recrystallizationfollowedbygraingrowthwouldrequiresufficientlylargedeformationsat a veryfewcentersinitiatingnewgrafns.

Regardlessofthisinitialmechanism,it canbepostulatedthatthecharacteristicshapeofthecurvesofgrainsizeversuspercentreductionby rollingresultsfranthefol-lawingsequenceofconditions:

(1)Inregionsofno reductionor smallerreductionsthanthecriticalsmountthereisnota sufficientcontrastinenergylevelstotie onlya fewgrainsgrowat theexpenseof surroundinggrains.Graingrowththatoccursis thenormaluniformgrowth.

(2)Theconditionsat thecriticaldeformationarediscussedabove.

(3) At so~whatlargeramountsofstrainthanthecritical,apyr-entlytherearemoregrainsina conditiontoabsorbtheirneighborsthan

28 NACATN4092

at thecritical.TheincreaseinthenumberresultsIncompetitionforavailablesurmountinggrains.Thegrainsizeisthenrestrictedbecausetherearenotenoughgrainsavailableforanyonetobecomelarge.

(4)At stilllergeramountsofstrain,normalrecrystallizationandgraingrowthmostcertainlytakeplace.Theeffectsat largermountsof strainare,however,complicatedifsimultaneousrecrystallizationoccursduringworking.Itappearedfromthedatathattherewaslittledifferenceinthegrainsizeineithercaseexceptwhena verysmallamountofrecrystallizationoccurred.Mixedgrainsizesresultedduringreheatinginthiscase,apparentlyby thefewinitialsmallgrainsgrowingat a fasterratethanthosewhichformedbyrecrystallization.Intheexperimentsconducted,}his~chanismdidnotdevelopabnormallylargegrainsalthoughitwastheoreticallypossible.Themechanism,however,seemedtobemainlyresponsibleformixedfineandcoarsegrains.

Inthediscussionofmethodsofavoidingabnormalgraingrowthitwaspointedoutthatrecrystallizationfollowedby criticalreductioncouldbe a sourceofabnormalgraingrowthunderconditionswherea morethancriticalreductionwasapparentlybeingrequired.Themechanisminvolvedapparentlywasno differentfromthatforthecaseofsmallreductionofinitiallystrain-freematerial,althoughtheremightbe dif-ferencesinthetemperaturesandtimesrequiredforabnormalgraingrowthduetounusuallysmallgrainsizeoftherecrystallizedmetal.

Thedatapredominatelyindicatedthattheemountofstrainandnotthestraingradientswasthecontrollingfactor.Thiswouldbe inaccordancewiththetheoryinvolved.

Theinfluenceofthepresenceofabno-llylargegrainsinthestructurebeforeworkingwasnotstudied.Suchgrainscouldbepresentbecauseoflackofrefinementfromingotstructureorbecauseof allowingabnormalgrowthtooccurduringpriorprocessing.Generalexperienceindicatesthatitis difficulttobreakupsuchisolatedlargegrains.Itis doubtful,however,thattheywouldcontributetoabnormalgraingrowthexceptinthecasewherelarge-scalecriticaldeformationsweresuperimposedoverthelargegrains.Apparently,wherelargerthancriticaldeformationsareinvolvedtheproperstraingradientdoesnotdevelop,orthesmountofcriticallystrainedmetalbetweenthelargegrainandsurroundingfinegrainissosmallthatnoappreciablegraingrowthoccurs.

Sincerateofgraingrowthincreasesasheat-treatingtemperatureincreases,abnormalgraingrowthcanoccurinlessthe atthehigherthanatthenormalsolution-treatingtemperatures.

NACATN 40!32 29

Metallurgicalvariableshadrelativelylittleeffectonabnormalgraingrowth.Variousprior-historyeffectscausedonlyminorvariationssolongas thepriorhistorydidnotincludemorethancriticaldeforma-tionwithoutan opportunityforstrainrelief.Grain-growthrestrainersas influencedby compositionandheattreat~nthadminoreffects.Therewassomeevidencethatmetal-flowcharacteristicsas influencedby tem-peratureandmetallurgicalvariablescausedminorchangesin criticalreductionandgrainsize.Certainheatingratesandtemperaturesappar-entlycanrestrictabnormalgraingrowth.

Themajordifferencebetweenthethreealloysstudiedwasthetemperatureandtimeperiodsforabnormalgraingrowth.InconelX-550alloyrequireda highertemperaturethandidtheothertwoalloys.Pre-smnablythiswasduetothegrain-growth-restrainingtendencyofthecolumbiumccmpoundspresentin thealloy.Thevacuum-meltedWaspaloydevelopedsmallergrainsthandidtheair-melted,possiblybecauseofthegrain-growthrestraintofa highercarboncontent.

CONCLUSIONS

Thefollowingresultsandconclusionswereobtainedfroman investi-gationtodeterminethebasiccausesofabnormalgraingrowthinair-andvacuum-meltedWaspaloy,InconelX-550,andNimonic80Aalloys:

. 1.Abnormalgraingrowthwasfoundto occurinWaspaloy,InconelX-550,andNimonic80Aalloysonlywhensmalldeformationscausedverylargegrainstogrowduringsubsequentheating.Thedeformationsinducingb abnormalgrowthusuallywerewithina rangeofreductionsof 0.4to5.0percents.ndwerewithina reductionrangeof 0.1to 9.7percentwhenallvariableswereconsidered.Normalsolutiontemperaturesandtimesaresufficientfortheabnormalgraingrowth.

2. Abnormalgraingrowthcanbe avoidedif careisexercisedtobesurethatallpartsofthemetalaredeformedmorethan10percentinanyoneworkingstepbeforereheating.Inmostcasesa reductionof5 percentwillbe sufficient.Theonlyexceptiontothisisthecasewherelargereductionscauserecrystallizationduringworkingandworkingis continuedunderconditionswhichwillcriticallydeformthestrain-freerecrystal-lizedmetal.

3. Themainprobleminavoidingabnormalgraingrowthse- tobe inrecognizingandavoidingconditionsleadingtocriticaldeformation.Itcanbe inducedby thethermalstressesofrapidcooling.Nonuniformmetal

●movementduringhot-workingleavingcertainsectionscriticallydeformedisa majorsourceof criticaldeformation.Attentionmustbe giventothe

.

30 NACATN40!32

designandmetalflowtoavoidcriticaldeformation.Particularcare *mustbe takentoavoidsmalldeformationsanddeformationgradientswhicharesuretoincludea criticaldeformation.Recrystallizationduringworkingandreheatingcanremovetheeffectofpreviousdeforma- .tionsothatitisimportanttoobtaina morethancriticaldeformation —

ineveryhot-workingoperation.

4. Thedevelopmentofsusceptibilitytoabnormalgraingrowthwasremarkablyindependentoftemperatureofwo~king.Deformationatroantemperaturehadthesameeffectasathot-workingtemperatures.Heatingtemperaturehadrelativelylittleeffectonabnormalgraingrowthpro-videdthetemperaturewashighenoughforthegrowthto occuratall.Becauseitcouldoccuratthenormalsolutiontemperaturesforthealloys,inadvertentexcessivelyhightemperaturesarenotnecessaryforitto occur.Inaddition,thesetemperaturesdonotcausesubstantiallylargergrainstoform.

UniversityofMichigan,AnnArbor,Mich.,September19,1957.

.

.

.

.

NACATN4082 31

REFERENCES

1.Rush,A. 1.,Freeman,J.W.,andWhite,A.E.: AbnormalGrainGrowthinS-816Alloy.NACATN2678,1952.

2.Anon.: ASTMStandards.PartI - FerrousMetals.A.S.T.M.(Philadelphia),1955.

3. hon.: Md&lS Eandbook.A.S.M.(Cleveland),1948.

k. Anon.:MetalInterfaces.A.S.M.(Cleveland),1952.

32 NACATN4082

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lUC~TN4082 35

(a)

.600

Taperedspecimenusedto obtain&pproMmatelyO-reduction.

to 15-percent

.600

(b)Taperedspecimenusedto obtainapproximatelyO-to 29-percentreduction.

. Figure1.-Taperedspecimensusedto obtainindicatedrangeofpercentreductionbybeingrolledto flatbars(dimensionsin inches).

.

IWCATNho82

.

(a)Approximatedistributionofgrainsizes.

.-.{

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L-57-3961Ftgure2.-Microstructureandgrainsizesoftransversesectionofas-

receivedair-meltedWaspaloybarstock.

.

.

.

.

, 1 4 1 #

Equalizing l’rea~nt of & -Received Stock

None Rolled 70%at L950”F

Heat

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Figure3.-Effect of heat-treatingtime ad temperature upon grain dze of transverse sectionsof air-meltedWaepaloy bar stock. 3

NACATN 4082

c14->8

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(c)Appro-te distributionof (d)MicrostI’uctmeasrolledgrainsizesasrolled50per- 70percentat 1,950°F,centat 1>950°F~ PIUS1 hour plus1 hourat1,950°F~at1,9500 F, thena ri -cooled. thenair-cooled.

cation,X50s

Figure4.-Microstructureandgrslnsizesoftransverseequalizedair-meltedWaspaloybarstock.

Magnifi-

L-57-3962sectionsof

.

39

.

.

c15-8

(a)Appro-te distributionofgrainsizesasro~ed.

c14-7

(b)Microstructureasrolled.Magnification,~.

(c)Approximatedistribution (d)Microstructureasrolled,ofgrainsizesasrolled, pluslhour atl,SOOF,plusthen

* Figure~..

lhour atl,~O°F, thenair-cooled.-Msgmifica-air-cooled. tion,50.

L-57-3963ticrostructuresandgrainsizesoftransversesectionsof

vacuum-meltedWaspaloybarstock.

Equaliz” ~ Treatient of Am-Received stock IRolled 70% ~ L950”F Rolled 25% at 80”F

+ 1 hour at 1950”F,+ 1 hour at ~950”F, water-quenched

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❑4.6

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Mgure 6.-Effect of repeated heating and cooling upon grain size of tram.werse sections of air-melteilWaspaloy bar stock.

.I

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L-57-3964Figure 7.- Effect of repeatedheating andcooJing uponmicrostructureof

air-melted Waspaloywhichhadbeen equalized by a 70-percentreductionat 1,~O” F. (Transversesectionatbar-stocksurface.) Magnifica-tion,X50.

Eqmdizing Treatment of As -R oiled Stock

Rolled at l,950°F from Z:inch ingot to 1/2-inch bar stock

+ 1 hour at L950”F,air-cooled

+ 1 hour at ~950°F,.water-quenched

❑4-7

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~igwe 8.-Effect of repeated heating and coollng upon grain size of transverse sectionsofvacuum-meltedWaapaloy bar stock.

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.

.

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,

.

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43

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.

. .

(d) 1 hourat 1,~0°F,water-quenched,plus1 cycleofk hoursat1,~00F, thenair-cooled. —L-57-39(j5

Figure9.-Effectofrepeatedheatingandcoolinguponmicrostructureofvacuum-meltedWaspaloywhichhadbeenrolledat 1,%0°F frcuna

2-inchingotto~- inchbarstock.(Transversesectionatbar-stock

surface.)Magnification,~0.

wliti.n Treatrn.nt of A.-Rece1.ed Sock Rolling Temp.r.mm for Tapered Speclrmnm Final Treatment [or Grain Growth

0 80”F❑ MO!YW I

Bfld 5G% u L950-F, + 1 houf ti I$S13.F, 4 1.6MWOWQumch.d o Lmu T 4 hoes at 1950”F, OitQubmcbed

● 1.95D°Fv

.6@?,O.F

x UOO°FI I I I I I I 1 I I I [ I I I I I I I I I I

4 ,

bb I I I I I I I1 2

I I4

I I I I I5 b

I I I7 8

I I I I I I I I9 10 11 12 a;

Percent RednclimW ItoUng

FQure 10.- Hfect of rolling tempemrture and ~cent” reduction upon maldmml grain size of aiZ-melted Waapaloy &er final ,soltiiontreatment.

, m, ,

NACATN4082

.

#

‘t,... .

.’ ‘..,-.: .-.-.-. -.* . .

/:, : . ‘. ,:. ,&. .

. ..L ,

,,\ ‘-<- -’ , ‘. ...’

1’

(a)Zero-percentreduction. (b) l.O-percentreduction.1.

t. ,, .

-..<t

.

,’,,.-

.

.

b

1.

. .. ..d? --,- \;,

. p f,. .. ...--!...,- ,--4, .,..

..-’ -,-j .-— ,

# ,—,-.-,.,. ..’,

* ..-,-.,.

...-.

(c) 1.5-percentreduction. (d) 13.O-percentreduction.L-57-3966

Figureil.- Effectofpercentreductionby rollingat l,~” F uponmicrostructureofequalizedair-meltedWaspaloyafterfinalsolutiontreatment.Equalizingtreatmentofas-receivedstockwasa ~-percentreductionat 1,~0°F plus1 hourat lj~OOF, thenoil-quenched.Finalsolutiontreatmentwas4 hoursat 1,~0°F, thenoil-quenched.Magnification,X50.

( -b

-4

4

f

c

z

rm

o MOOT

Hnch-dmnet.r imgc.trdlcd .t 1$50-F la 3/4-inch bar .tc.ck 0 WOO.F

+ 1 hour at 1950”17, Ai_oled & L900”F4kur8 at 1,950.F. Oil-Quench.d

o F&loo.rI I I I I I I I I I I i I I I I I I I I I I I

I I I I I I I I I I I I I I I I I I I I I I I I 1

1 2 3 4 5 b 7 8 9 10 11 12 r!

Perccmt Re=ductim & Rolling

Figwe K!.- Eff’ectof rolling temperature and percent reduction upon maximum grain size ofvacuum-meltedWaqXlc3y efter final solutiontreatment.

●

‘1* t

lllm.lim 4082 47

. .. . .

t

,,

.- . .. 1, “,J ,,

,.~ ,.;

..” -. #L ,-

... . ., ., ,..,

, ,. t, ’.’,. ,-.“. . .,. .

..!’”.“ . ----’ .s. . . .

. ..,’. .,. . . .t“’., .. .!. . .. .

●

✎ ✎

.,..-.,i :-’ ..... , , I

. . ..’.r .. ”:,.. .-

; . . . . . . .

. ,

..- *..

reduction.(a)Zero-percent (b) O.6-percentreduction.

. .“,.

● . ,.., :’.:

. . . . . . . ‘L. ...-

‘. .-, .-

~.,,. . ,., .

“...;. J. .

. . . .,..“. .. . ..

.i. ,... ..””

. ..”-. .+.

. . . ,,. .

,-,.- =,-

. .. . . . .. ..? .:.’ #\:.;’._ . ‘+ ”..

,, L,, .m:,“. ., ..

.- . . ,“, . . ...1.I,., ,,. . . . . . . 1-.. :,. .

,.

,

(c) 0.8-percentreduqtion. (d) 6.1-percentreduction.L-57-3967

Figure13.- Effectofpercentreductionbyrollingat l,gOOOF uponmicrostmctureofvacuum-meltedWaspal.oyafterfinalsolutiontreat-ment. Equalizingtreatmentofas-rolledstockwas1 hourat 1,~0° F,thenair-cooled.Finalsolutiontreatmentwas4 hoursat l,~o F,thenoil-quenched.l&gnification,Xx.

-.

Heat Tred.mento None

● None — 80.F _ 411L.ml’flat 2950”F, Wgllenclm

Rolled 5M -t 2950”S0 1 hour at1,950-F, AiI-bc,led -+--2$00”s —-- Mow-he&d from MOO-F to 2,99(

A ] hour at L950-F, Oih@_h9d in 3 honrs + 4 hour. at 4950.F,Mr-C.ooled

-6 I I I I I I I I 1 I I 1 I I I I I I I I I I

I

t

I——— —.- _____ _____ ____

4

b- 1 I I I I I I I I I I I I I I I I I I I I I I I I0 1 2 3 4 5 6 a 9 10 11 12

P.rcm.,t neductlcw~rloning

Figure l!+.-Effectofequalizingtreatment,rollingtemperature,@?centreduction,andheatIngratebeforefinalsolutiontreatment.uponm.xlmumgrainsizeofair-meltedWaspeloyafterfinalsoluticmtreatment.

, , d I

, v *

ii!

-bI

II I I I I I I I I

t

‘4t m--q.

—O— J.901J-F Ic1----~g~.p—A— UOO”F

4 hon., .t 4950-F, Oi!rQuembd

--- V~”F

I I I I I I I I I I I I

I-2

0

4

6 I I I I Io 1 2

I I3

1 I I I I I I I I5 7

I I I f I I I9 10 IJ

I I12 13

Pemcnt B.ednctin by RoUA~

Figure ~.. Effeet of equalizingtreatment,rolling temperaimre, and percent~ grainsizeOf air-meltedWaapaloytier fimil.solution~reatm~nt.

0Q9 oil-quenched.

reduction uponAC, air-cooled;

!3~R’

—

E, udldm Treatmmt cdAs-Receiv~st~ Inollmg

I rim 1 ~nt f.yr Gr~ir. Growth

Heat Trentment —0— fboo”F

— R&mated 1 /.? hour at —D— %100”F 4 hour. at 1950 ‘F, CdFQ..nched

Rolled 5~ at 1.950”F ZIOO”F --d-- Moo”r--- 1 how at 4950-F, Gil-

13Uencbod–-0-- 2JO0.F

-6I I I I I I I I I 1 1 I I I 1 1 I I I I 1 1

-4

I

I0-0 %2<

‘%.-.

‘A—— ----- ——--&------

-. --d —-—--- --a

b 1 I I I I I I I I 1 1 I I I I I I 1 I I I I I I I

o 1 z 3 4 10 11 12

P.rcnnt R.duction by Ro13Jng

Figure16.-Effectofequalizingtreatment,rollb ~meratme> ad P=cefireductionUPOIZmaxbm grainsizeofair-meltedWaspalOyafterfinalsolu~i$mtreatmeti.

,. ,

.

, , * I

r , , t

.6

FiM2 Tremtment fur GrmIn Growtho A8 rmc~iwd

Heat Tre.tmeti❑ Bo12ad 25s M 80”F

& Boll.d 25% *t l&OO°F 1 hour .t 1950 ‘F, OIIQ.enchcd &600”F 4 honm at 2.950.F, W-@mched

O Rolhd 25% nt I)950”F

● Rolled 50% u 1#50”F

I I I I I I I I I I I I I 1 I I I I I I I I I

-4+ J I I I I I I I I I I I I I I I II I I I I

2 3 4 5 6 8 Y 10I

11 1A 1

Pmrcent Rcducd.m by Fto2UnE

Figure 17.-Effectofequalizingtreatmentandpercentreductionby rollingat1.,6~0F uponmmd.mmgrainsizeofair-meltedWaepaloytier fhml.solutiontreatment.

WIr

NACATN4082~=

EqualizingTreatmentofAs-ReceivedStock

1hourat1,950‘F,oil-quenched,+ 2570reductionat80”F,+ 1 houratL950”F,oil-quenched

TensileTest Elongation, ApproximateDistributionofGrainSizes

Temper- percent AfterFinalSolutionTreatment.ture,“F

1,400100 W

1,600 1.0 2-6tIII11

m

4600 2.5 2-6

FinalTreatmentforGrainGrowth

4 hoursat1,950”F, oil-quenched

Figure18.- Effectoftemperatureandpercentelongationbytensiletestingupongrainsizeofair-meltedWaspaloyafterfinalsolutiontreatment.

.

.

.

.

“1, , ● ✃

● 1

4WIMU Trc@ncrdof FI..1 Tr.mmenl for ~rminOm-th

Heat Treatm.nc— 1 hour ●t $975-T. — I,S50.F — 4 how, at L975-F, Air-Cooled

AirCwlKI .,--Rolled w% x I,950”F

J,850.F---;i~~;,950.F, --- Skaw-baud krom 1400-F to L950-F in 3 ho.,. +

— MO-L? 4 hour. ●t U190-F, A1r-Cmlmd

— w50”r

.6 1 1 t 1 I 1 1 I I 1 I I 1 I 1 1 I # I I I I I I I

-4\

-\

. -z:m~

1!ux 0-

4

6} 1 I I I I I 1 I ! I I I I I I 1 I I I I I I 1 I I I1 3 5 6 7 9 Jo 11 14 15 16 17 L’8 19 20 21 22 23 ;4 Z5 26 .?1 2d .2-$

%re.mt Redmdm W ReUiW

Figure 19.-Effectofrollingtemperatureaudpercentreductionupcmmaximumgrainsizeofair-meltedWas@loytier ftrial.solutionWeatmmt.

* NACATN40&

.

. . .I

. . .. . . . . -

. .,

●

6h

‘“ ‘1 :u.

,-i

... . . *.. “...“

. .. . &k , .. . . . . . -

,, .“

,.-

,.t

. . . . . .. .. ..... ..-..

.,. ,.. -,..

asrolled.

,-‘,

“,,.-

.-.. .i

(a)Microstructure (b)Microstructureas rolled.. .14-percentreduction;rolledat1,8500F.Magnification,X50.

lk-percentreduction;~olledat1,850°F.Magnification,WO.

.._,-,..

: . .4

.1,. .

.

,.. ,’. i. .:,+;.. .

‘,f1

.-,..’.

.+it .;-.:..

-..:..--.;’. ,. .

**

b’,I

.A

. ,.-.. . .

,

. .“-=.,. (

:.>. “(

, .-.l~. ,-.

,..

.’ L’ L””’-e- +..

~..,.~ ‘...

-5. ... . ..

. . . ..-.”

,.. . . . ..- ‘“,,. . .

t-., -,..<

,.

- <-”....- ::. ,,;.. t. . . ..,:.!. .

.

...-1

. . “,,..W”,.,

Microstructureafterfinalsolutiontreatment.14-percent12edUCtiOlljrolledat1,850° F. Magnification,X50.

L-57-3968 “Figure20.-Effectofpartialsimultaneousrecrystallizationduringreduc-

tionby rollingat1,8500and1,~0°F upongrainsizeofair-meltedWaspaloyafterfinalsolutiontreatmentof4 hoursat 1,975°F, then 4air-cooled.

NAC!ATN4082 55

.

. .... ----

,-—.”..

.. -,.-.-”. -

.-

(d)Microstructureasrolled.16-percentreduction;rolledat 1,~0°F.Magnification,Xx.

.

,

.

. .-

,,

~,

(;-.

JW’P“;

,- . . .-..,. ,

~.-,.. ”

*’R.. . .

.-. . .. .

(e)Microstructureasrolled.16-percentreduction;rolledat 1,~0°F.Magnification,X5~.

,...F-”

(f)Microstructureafterfinalsolutiontreatment.16-percentreduction;rolledat 1,~“ F. Magnification,~0.

L-57-3969Figure20.- Concluded.

MCAm 40&

70

60

50

40

30

20

10

0

I I 1 I I I I I I

.

Rollingtemperaturefor taperedspecimens‘F

o 4850A A 1,950

~ 2Q50

I 1 I Io 30 40

PercentReductionby Rolling

Figure21.- Effectofpercentreductionby rollinguponyercentsimulta-.

neousrecrystallizationofair-meltedWaspaloy..

.- .-

, , * 1

As-Received

u6-8

I-l~at-Treating Heat Treating Time, hr

T.:mperqture,“F

1 6

’900 ‘m ,-,ti 1-3KZZl!l

4)”1] :IZ?iZ!!—-—

‘Jo ‘“-a -+1= E5 , -“m. . . . . ..—

‘./00

El

0-4

. .-— . . ....,-.. —.. — ,L-,.

L-1. . . . . . . :. :“,.. ~,r~w:).t-treatingblme and temperature upon grain size m? transverse sectionsof t:c-impivedInconel x-~~ b= stock. :

58 MCATN4082

.

●

.

.

,.

6-8

(a)Approximatedistributionofgr~n sizesasreceived:

(b)Microstructureasreceived.Magnification,DO.

.

7-8

(c)Approximatedistribution (d)Microstructureasreceivedofgrainsizesasreceived plus2 hoursat1,90°F,plus2 hoursatl,w” F, thenair-cooled.(Centerthenair-cooled. ofbarstock.)Magnifica-

tion,xx.L-77-3970

Figure23.-MicrostructureandgrainsizesoftransversesectionsofInconelX-550bsrstock.

.

.

.

.. .

. .

---- ..,

.

.. ..

/-(-3)-”1

(e)Approximatedistributionofgrainsizesasreceivedplus2 hoursat2,1~0F, thenair-cooled.

-. ,,,. f... ..- , k

..“

.

,“....

(f)Microstructureasreceivedplus2 hoursat 2,100°F,thenair-cooled.(Junctionbetweenfineandcoarsegrains.)Magnification,~o.

Figure23.-

J“” .,—.. . .

(g) MicrOstncture as receivedplus2 hoursat 2,100°F,thenair-cooled.(Centerofbarstock.)Magnifica-tion,~0. -

Concluded.

L-57-3971

Aa-EquAWed

❑5-8

Cooling Method

HeatTreatment

AirCooled Water-Quenched

One cycle of1 hour at U50”F, ❑o-4

n

0-4

coaled

Two cycles of1 hour at U50”F,

•1

o-4 (-3)-2

a

@g ; 0-4cooled

Three cycleo of

0

(-1)-2

1 hour,at 2J50”F,cooled 0-4 (-3)-2

%ETi

o-4

Four cycles of1 hour at 2J50”F,

cooled (-1)-2

B

o-4 (-3)-2

s

0.3

Five cyclee of1 hour at 2J50”F,

cooled (-2)-2

*

o-4 (4)-(-1)

w

2-3

Figure 24.- EfTectorrepeatedheatingandcoolingupongrainsizeoftransversesectionsofInconelX-570barstockwhichhadbeenegwilizedby a fkpercentreductionat2,150°F. i

. , . 1 . t

“

.

.“3.’”’ ‘

., , ..~. . . .

,.. .“ 1. .,., ,:~

,..I

,,

● ▼

!i. . .J,~, 7,.

>’,.

‘‘-’!..-.,!,

.,,.,

,., , “,, --:.,.’”-’ ,,*!,, --JL, 1,’”” . { ,-”: :

,’. ,-,,. ... , . .,

!,,.,

,. .-. ,””.,.

t?...,.i.,

. .-.

,.!

.:. ,...’,

., .

_;. /” -“.,’ .1’. ,,,

,..

.,

..

.

—.,. + .../

?,

,.

1-

I

,.’. ,

I

1’

r

,.,.

..

.i

,

#

,1

-.

, #

,.

.:--.

I

.

,,,’

‘1

..

. .

I

Em.ck w:=wKR&’”r I Fhm2 Treatm.mt for Grain Growth

I o J400”F2 hours ●t J,900 ‘F, Air-tided A l#OO-F

H WOO.F1 hour d 7,150.F, .4bGx&d

o 2.ZOO.F

-1

-6I I I I I I I I

II I I I I

II I I I I I I I

-4

0--

-2

0

1-(

z . \

6 I I I1

I I I I2 3

I I I I4 5

I I I I I I I I I I I I I I9 10 JJ 12 1

(a)

F@Ire 26.-Effect of

Percent Red.ctim by Rolbg

Grati size after eqyali.zingtreatuwrt was 7 to 8.

rolling temperature and percent reduction upon maximum .grKinsize ofInconel X-~~ at%er final solutiontreatment.

. , . , ,

, t

-.

*

Equalizing Tr?atrmnt of As -Received 9Lock

o l#ooTA l#OO”F

2 how. ●t ~ OO-F, Air-Cooled❑ 2,000-F 1 hour at U50-F, Ai~d

I I I-6 I I I I I I I I I

II I I I I

II I I I I I I I I

-4

: -2a~

:

:0

%

5E

{2 -

4

6 I I I I I I I I I I I 1 I I I I I/

o 1 2I I I

3 4I

5 6I I I

7 8 9 10 11 12 19

(b) Grain size

Percent Reduction ky ROIZ@

fier equalj.zj.ngtreatment was O to 5.

Figure %. - Continued.

I O Trmmferred tn f,bOO-3?Rolled 50% at 1950-F, AiKaol.d 4 112 hour preheat furuc. and M l12hIxtr,

M Uoo. s!

Rollad It J,600WA ~OUd at ~oo.~

1 ham at ?.150-F, Air-Cco2ad

i.

t“’’’’’’’’’~’’lll~lllll,,

I I I I I 1 I I5

I I6

I I7

I I8

1 I9 10

I11 12 13

P.rcent Rcduclian by Ro12iq

(cJ Equalizingtreatmentinehuledrollingat1,~“ F andpreheatat2,100°F.

Figure 26.- concluded.

● ,L

II ‘ ‘ ,,

9R

.

NACATN40&

. ,-

.● ✎ ✎

a .,.

.> 1

.

.

‘,

>.

.. .

1 ., :

(a)Zero-percentreduction.,

i*’“1 t

.-+ ..-.-.

-.-, %*

–.! .:..,:=..-,

?“b

65

●

(b) 4.O-percentreduction.

,, c’”,; [,‘r.&

—. .-? .“i

i

. -.*{

(c) 11.1-percentreduction. L-57-3973

Figure27.- Effectofpercentreductionby rollingat 2,100°F uponmicrostructureofecymlizedInconelX-550afterfinalsolutiontreat-ment. Equalizingtreatmentofas-receivedstockwasa 50-percent

0 F beforerolling.1 hourpreheatat 2,100reductionat 1,~ 0 F phlS~-

Finalsolutiontreatmentwas1 hou at 2~150°F) thena~-cooled~Magnification,X50.

-.

An-Received

ob-8R

Heat.Treatimg, Heat-Treating Tim% hr

Temperature“F

1 4 6

L950 o1-30-2

@

● o

2JO01.3*

6* ●

4150

‘-z’-’-u@ ‘-’)-o@

Q

● 98

?200 (-1} 60-2.● *

42%’

(-1)-0

~oo (-Z)-2

Figure 28.- Effect of heat-treatingthe and temperatureupon grain size of transverse sections 4=of as-received Nimonic80Abez stock. E

. , b r ,

NACATN4082 67

.

.

b

.

.

0(5./3

(a)Approximatedistributionofgrainsizesasreceived.

n3->8

~f$ .*.. ,. . . ‘ , . . . . .

w. “’.. i“ .. .....=.. . ---+ .-:~.. . 22>. -“” ”-”.’ ‘

‘?-%-”,:“: &-@.’..--, +

----S’ ~

-. *..-.-,”:.

.r : “4..,.-

(b)Microstructureasreceived.Magnification,50.

, ,.m.

.

.

,-

(C}Approximatedistribution (d)Microstructureafterofgrainsizesafter equalizingwith~0-percentequalizingwith50-percent reductionat 1,~0°F plusreductionatl,~” F plus 1 hourat 1,~0°F, then1 houratl,~” F, then air-cooled.Magnification,air-cooled. m.

L-57-3974Figure29.-Microstructuresandgrainsizesoftransversesectionsof

as-receivedandequalizedNimonic80Abarstock.

E.Jd!%lu Tremtumnt of A,.Peccived Rbxk Rollw (kadiU_ for Tapac.f Speclmem Final Tr.-t 6X Grmln Growth

~L750 -F. -w. — 4 hour. at 1975-F, Aifi.wlad

~wo.r. m ps v-.- 4 homa a IWO-F, W.mlsd

-.-A--Ls9o”r. MMw,RoUdd 50S at L950-F+

—. —.- SlO!-h@4d frm L400-F 10 J,Y50-F in 3 hwr,

1 ham at Jj50.F, AII-CC.OIA--Q-L950.T, _ w. + 4 how. u I,950T, A18-C+Ad

–-0--M5O.F, we w..., .me r.ha.e

-6 I I I I I I I I I I I I I I i I I I I I I I I I I I

6 I I I I I I I I I I I I I I I I I I [ I I I I I I I 1 I0123456 70910111213 1416 16 17 1* 19 20 21 .?2 2j .?4 25 24 27 2U d

P.rcem R.dmcfioa b, RelUnE

Figure 3.- E&fect of temperate and percent reduction by rollhgj repeated deformationbyrolMng, ad heating rate before final solutiontreatment upon ?mxinnm gxain size ofTHmonic 80A slloy after final solutiontreatment.

* , . ,, ,

# , . ,

Figure 31.-Effect of degree of taper, repeated deformation,and percent reduction by roILlng

upon maximum grain i3izeof Mmonic MA alloy at%er final 6oluti.cmtreatment.

CJ 1 m .t 2. WCI-F. NFCmkd

O 1 hcur ,, .2m0.r; Ab-Oaald

Nab. J.954hF & 1 hour ,. .?.250-F, Aa--(k-ald

~ 1 hoe., 2300T, Air-faolBd

. Sbw—hud (M 1,950.Fto 2,990-F i. 1 E-mm +1 homr It uOOxT, Afl-coakd

I I I I I I I I I I I I I I I I I I I I I I I I I I

I 1- 1 I 1. I I.. L I I 1 4 I I 1 1 1 I I I I I I I I I I I12 45 7 8 9 ia 11 12 13 14 15 16 17 18 19 20 .?1 .?.? .?3 24 25 .?6 2-/ .38 2!

Percent B-tin by P.olHq

Figw.’e32.-Effect of fi?wl solutiontreatmetitsndpercentreductionby rollinguponmaximumEs

grainSizeof~imoml.cW elloy.=!r

B

●

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