材控专业英语3principles of plastic forming

Chapter3PrinciplesofPlasticforming3.1PhysicalMetallurgyofHotWorkingWordsandterms:physicalmetallurgy物理冶金rolling轧制,轧件(steelrolling)workhardening加工硬化staticrecovery静态回复thermallyactivated热激活的Drivingforce驱动力

hotworking热加工dynamicsoftening动态软化

recrystallization再结晶

dislocationdensity位错密度copper-basealloy铜基合金

criticalstrain临界应变Chapter3PrinciplesofPlasticforming3.1PhysicalMetallurgyofHotWorkingHotworking

referstoprocesseswheremetalsareplasticallydeformedabovetheirrecrystallizationtemperature.Beingabovetherecrystallizationtemperatureallowsthematerialtorecrystallizeduringdeformation.Recovery

isaprocessbywhichdeformedgrainscanreducetheirstoredenergybytheremovalorrearrangementofdefectsintheircrystalstructure.Thesedefects,primarilydislocations,areintroducedbyplasticdeformationofthematerialandacttoincreasetheyieldstrengthofamaterial.Recrystallizationisaprocessbywhichdeformedgrainsarereplacedbyanewsetofundeformedgrainsthatnucleateandgrowuntiltheoriginalgrainshavebeenentirelyconsumed.HotplasticformingHotplasticformingHotplasticformingHotplasticformingHotplasticformingPhysicalmetallurgyofhotworkingSchematicofarollingprocessrollworkpieceDeformedelongatedgrainsNewgrainsformingandgrowingRecrystallizationcompleteRecovery,Recrystallizationandgraingrowth3.1Physicalmetallurgyofhotworking热加工的物理冶金原理已被人们所熟知。在变形过程中，例如轧制过程虽然发生了加工硬化，但通过回复和再结晶的动态软

化过程维持平衡。Theprinciplesofthephysicalmetallurgyofhotworkingarenowwellrecognized.Duringthedeformationprocessitself,e.g.,arollingpass,workhardeningtakesplacebutisbalancedbythedynamicsofteningprocessesofrecoveryandrecrystallization.3.1Physicalmetallurgyofhotworking这些热激活过程，产生流动应力，流动应力取决于应变率和温度以及应变。Theseprocesses,whicharethermallyactivated,leadtoaflowstressthatdependsonstrainrateandtemperatureaswellasonstrain.Thestructuralchangestakingplacewithinthematerialresultinanincreasingdislocationdensitywithstrainuntilinausteniticsteelsandnickel-andcopper-basealloysacriticalstrain（εc）isreachedwhenthestoredenergyissufficientlyhightocausedynamicrecrystallization.材料内结构的变化产生应变，导致位错密度增加。在奥氏体钢和镍基、铜基合金中，当储存能量足够高时会发生动态再结晶，材料达到临界应变εc，这时位错密度不再增加。

长句变短句，注意其中的意思连贯3.1Physicalmetallurgyofhotworking3.1PhysicalmetallurgyofhotworkingWithfurtherstrain,dynamicrecrystallizationtakesplacerepeatedlyasthenewrecrystallizedgrainsarethemselveswork-hardenedtothecriticallevelofstoredenergy.随着材料发生进一步的应变，由于新的再结晶晶粒本身发生加工硬化，使储存能量达到临界水平，动态再结晶重复发生。这些动态的结构变化使金属处于不稳定状态，并提供变形后发生静态回复和静态再结晶的驱动力，如果温度足够高，静态再结晶之后还会发生晶粒长大。Thesedynamicstructuralchangesleavethemetalinanunstablestateandprovidethedrivingforceforstaticrecoveryandstaticrecrystallizationtotakeplaceafterthedeformationpass.Staticrecrystallizationmaybefollowedbygraingrowthifthetemperatureissufficientlyhigh.3.1Physicalmetallurgyofhotworking3.1Physicalmetallurgyofhotworking为了在商业制作过程中应用这些原理，我们需要回答两个主要的问题：a变形之后再结晶需要多久才能发生？b再结晶和长大之后的晶粒尺寸是多少？Inordertobeabletoapplytheseprinciplestocommercialworkingprocess,werequireanswerstotwomainquestions:ahowlongdoesrecrystallizationtakeplaceafteradeformationpass;andbwhatgrainsizeisproducedbyrecrystallizationandgraingrowth?Theanswersdeterminethestructureofthematerialenteringthenextandsubsequentpassesandhenceinfluencetheflowstressofthematerialandtheworkingforcesrequired.Eventuallytheydeterminethestructureandpropertiesofthehotworkedproducts.答案决定了材料进行下一步以及随后过程的组织，并影响了材料的流动应力和需要的作用力。最终影响了热加工产品的结构和性能。3.1Physicalmetallurgyofhotworking3.1.1DynamicstructuralchangesWordsandterms:Initialgrainsize原始晶粒尺寸Torsion扭转，转矩Stress-straincurve应力应变曲线Activationenergy激活能Duringthedeformationofausteniteathot-workingtemperaturesandconstantstrainrate,thecharacteristicformofstress-straincurveobservedisillistratedinFig3.1.在处于热加工温度和恒应变率的奥氏体变形期间，得到的应力-应变曲线如图3.1所示。3.1.1DynamicstructuralchangesFig3.1Equivalentstress/equivalenttensilestraincurvesobtainedFromtorsiontestsonlow-alloysteels(AISI1540)ofinitialgrainsize110μm3.1.1DynamicstructuralchangesThesecurvesareforlow-alloysteels,testedintorsion,butaresimilartothose

obtainedforothersteelsintheausteniticconditiontestedintorsion,tension,orcompression.这些曲线针对测试扭力的低合金钢，但却与其他奥氏体状态的钢在扭力，拉伸或者压缩方面相似。Afterinitialrapidwork-hardeningthecurvesgothroughamaximumassociatedwiththeoccurrenceofdynamicrecrystallization.经过起初的快速加工硬化之后，曲线中的应变达到最大值，这与动态再结晶有关。3.1.1Dynamicstructuralchanges小部分再结晶发生之后，产生流动应力的峰值，峰值处的应变εp总是大于动态再结晶εc的临界应变。Thepeakinflowstressoccursaftersomelowfractionofrecrystallizationhastakenplacesothestraintothepeak(εp)isalwaysgreaterthanthecriticalstrainfordynamicrecrystallization(εc).两种应变之间的关系很复杂，但对于热加工变形态来说，可以通过εc=αεp

近似表示（α是常数）。Therelationshipbetweenthetwostrainsiscomplex,butithasbeensuggestedthatεc=αεp

(whereαisaconstant)isareasonableapproximationforconditionsofdeformationofinterestinhotworking.3.1.1Dynamicstructuralchanges但是，α的建议值并不一样（动词），可能是0.83,0.86或者0.67。从图3.1中可以看出，随着

ZenerHollomon参数Z增加（不依赖于关系式中应变率和温度的组合），εp系统地增加。However,theproposedvaluesofαdiffer,being0.83,0.86,and0.67.ItcanbeseenfromFig.3.1thatεpincreasingsystematicallywithZenerHollomonparameter(Z),independentoftheparticularcombinationofstrainrate(ε)andtemperature(T/K)intherelationship.3.1.1DynamicstructuralchangesWheretheactivationenergyQdefforthisalloysteelis314kJ/mol.Asimilarvalueof312kJ/molisappropriateforarangeofC-Mnsteels.Butlowervaluesof270and286kJ/molhavealsobeenobserved.式中，该合金钢的激活能Qdef为314kJ/mol。碳-锰钢的激活能大概是312kJ/mol，但也观察到270和286kJ/mol的低值。3.1.1Dynamicstructuralchangesεc表示亚晶粒的微观结构变化，亚晶粒不发达，由加工硬化和动态再结晶产生。亚晶粒还包括再结晶形核，根据变形后静态结构的变化可知，亚晶粒也是一种临界应变。

Asεc

marksachangeinmicrostructurefromoneofsomewhatpoorlydevelopedsubgrains,producedbytheactionofworkhardeninganddynamicrecovery,toonewhichalsocontainsrecrystallizationnuclei,itisalsoacriticalstrainintermsofthestaticstructuralchangesthattakeplaceafterdeformation.3.1.1Dynamicstructuralchanges低合金钢和一些碳-锰钢的εp和εc与Z的关系如图3.2所示。从图3.2中可以看出，尽管Sakui等在Z=3×1010/s时（Qdef=312kcal/mol）得到εp的最小值，但随着Z的增加，εp

总体是增加的。

Thedependenceofεp,andhenceofεc,onZ

isshownforthelow-alloysteelandanumberofC-MnsteelsinFig3.2.Itcanbeseenthat,asindicatedbytheFig.3.2,εpgenerallyincreaseswithincreasingZalthoughthecurveforthedataofSakuietal.passesthroughaminimumatZ=3×1010/s(correctedtoQdef=312kcal/mol.3.1.1DynamicstructuralchangesFig3.2dependenceofpeakstrain

εponZ3.1.1Dynamicstructuralchanges根据Nakamura和Ueki,Cook,Rossard和Blain,以及Hughes,还有Suzuki等获得的一部分碳-锰钢的数据可知，曲线由测试获得，将材料重新加热至相同温度作为测试温度。

ThecurveforthedataofNakamuraandUeki,Cook,RossardandBlain,andHughes,andalsothedataofSuzukietal.foranumberofC-Mnsteelswereobtainedfromtestsonmaterialreheatedtothesametemperatureasthetestingtemperature.3.1.1Dynamicstructuralchanges这些数据也表明一种趋势，即较高的测试温度下，

εp值也较高。与之相反，

根据LeBonetal.,Barraclough,和Morrision的测试数据可知，曲线在低于重新加热温度完成，这表明测试温度对εp没有影响。Theseallshowatrendforhighervaluesofεpathighertestingtemperatures.Incontrast,thecurvesforthedataofLeBonetal.,Barraclough,andMorrisionrefertotestscarriedoutatlowertemperaturethanthereheatingtemperatureandtheseshownoeffectoftesttemperatureon

εp.3.1.1Dynamicstructuralchanges前者团队的结果得出，重新加热/测试温度越高，起始晶粒尺寸越大。如Sah等和Roberts等的研究表明，晶粒尺寸增加导致εp的增加，他们的数据得出了一个关系式。Intheformergroupofresults,higherreheating/testtemperaturewillgivelargerinitialgrainsizes.AsshownbySahetal,andRobertsetal,increaseingrainsize(d0)leadstoanincreaseinεpandtheirdataindicatearelationoftheform.3.1.1DynamicstructuralchangesHoldingtemperature保温温度Holdingtime保温时间Metallographic金相的Straindependence对应变的依赖Subgrainboundary亚晶界Nucleationrate成核率Yieldorflowstress屈服或流动应力Restorationindex回复指标Order

ofmagnitude数量级Systematicstudy系统研究Drivingforce驱动力Metadymatic亚动态的3.1.2StaticRecrystallizationRate3.1.2StaticRecrystallizationRate变形后，随着时间和速率（依赖于前期变形态和保温时间）增加，静态回复和再结晶引起软化。Afterdeformation,softeningbystaticrecoveryandrecrystallizationtakeplacewithtimeatrateswhichdependonthepriordeformationconditionsandtheholdingtemperature.这些过程可以研究再次变形期间不同保温时间内屈服或流动应力的变化，以获得回复指标，或者可能通过淬火样品的金相实验直接测量再结晶。Theseprocessesmaybefollowedbystudyingthechangesinyieldorflowstressduringaseconddeformationgivenafterdifferentholdingtimes

toobtainarestorationindex,orrecrystallizationmaybemeasureddirectlybymetallographicexaminationofquenchedspecimens.3.1.2StaticRecrystallizationRate采用后者办法获得的低合金钢的再结晶曲线如图3.3所示。曲线一般遵从阿夫拉米方程，XV=1-exp[-C(t/tF)k

]，式中，XV

表示时间t内再结晶的部分，tF是特定部分再结晶的时间(一般为0.5);k

是常数;C=-ln(1-F)。对于所示曲线来说，k=2，这与其他钢变形到低于εc

的应变获得的值一致。Anexampleoftheformofrecrystallizationcurvesobtainedbythelattermethodforalow-alloysteelisshowninFig3.3.ThecurvesgenerallyfollowanAvramiequationoftheformXV=1-exp[-C(t/tF)k

]whereXVisthefractionrecrystallizedintimet;tFisthetimeforsomespecifiedfractionofrecrystallization(say0.5);kisaconstant;andC=-ln(1-F).Forthecurvesshownk=2,whichisconsistentwiththevalueobservedforothersteelsdeformedtostrain＜εc.33XV=1-exp[-C(t/tF)k

]Fractionofrecrystallizationthetimeforsomespecifiedfractionofrecrystallization3.1.2StaticRecrystallizationRate3.1.2StaticRecrystallizationRate根据这个关系式，t0.05=0.27t0.5

，t0.95=2.08t0.5，即，再结晶在一个数量级的时间内进行。Withthisrelationshipt0.05=0.27t0.5andt0.95=2.08t0.5,i.e.,recrystallizationproceedsoveraboutoneorderofmagnitudeintime.3.1.2StaticRecrystallizationRate通过金相或者回复方法获得的几种钢的应变与特征时间t0.05=的关系如图3.4所示。Thedependenceonstrainofthecharacteristictimet0.05,measuredbyeithermetallographicorrestorationmethod,isshownforseveralsteelsinFig3.4.所有的曲线表明，t0.5∝ε-m（m的平均值=4），随着应变增加，t0.5迅速降低，直到0.8εp。Allthecurvesshowasteepdependenceonstrainforstrainsupto~0.8εp,whichfitsaralationshipt0.5∝ε-m,wherethemeanvalueofm=4.Fig3.4Dependenceoftimefor50%recrystallizationorRestorationonstrainforC-Mnandlow-alloysteel3.1.2StaticRecrystallizationRate从铁素体的观察中也发现同样的值。在关系式应用中，由于没有系统研究静态再结晶的临界应变，应变的下限并不确定。Thisvalueisalsogivenbyobservationonferriticmetals.Thelowerlimitofstraintowhichthisrelationshipisapplicableisuncertain(asthecriticalstrainforstaticrecrystallizationhasnotreceivedsystematicstudy).3.1.2StaticRecrystallizationRateNorrison的数据表明，对于低碳钢在950℃应变的下限＜0.05，而Djaic和Jonas的研究则表明，高碳钢在780℃应变的下限＞0.055。ThedataofNorrisonindicatethatitis＜0.05forlow-carbonsteelat950℃whereastheobservationsofDjaicandJonasindicateavalueof＞0.055forhigh-carbonsteelat780℃.ItisnotclearwhetherthisdifferencearisesfromthedifferenceintemperatureorcompositionasthesimpledependenceonZsuggestedbythebrokenlineinFig3.2maybeunrealistic（不切实际，不现实）.由于图3.2中折/虚线引起的Z的变化可能不存在，因此温度或者成分引起的不同（应变）并不清楚。3.1.2StaticRecrystallizationRate应变的下限值得进一步研究。低的应变可能应用于板材轧制的终轧孔型，如前所述，如果低应变超过静态再结晶的临界应变，对最终的晶粒尺寸有重要影响。Thisdeservesfurtherstudyaslowstrainsmaybeappliedinthefinalpassesofplaterollingand,asshownpreviously,thesecouldhavesignificanteffectsonthefinalgrainsizeiftheyexceedthecriticalstrainforstaticrecrystallization.3.1.2StaticRecrystallizationRate在t0.5随ε急剧变化的应变范围内，

Morrison发现，高于两个数量级之后，应变速率没有影响。这有点令人惊讶，因为在任何特定的应变下，关注的应变速率或者Z

增加了流动应力。Inthestrainrangeofsteepdependenceoft0.5onε,Morrisonobservedthattherewasnoeffectofstrainrateoverthetwoordersofmagnitudestudied.Thisissomewhatsurprisingasinterestingstrainrate(orZ)increasestheflowstressatanyparticularstrain.3.1.2StaticRecrystallizationRate流动应力的增加有望增加无序的位错密度，降低亚晶粒的尺寸，由此提高了储存能量。Increasingflowstresswouldbeexpectedtoincreasetherandomdislocationdensityanddecreasethesubgrainsizeandhenceincreasethestoredenergy.Thesubgrainboundariesprovidethelargestcontributiontothestoredenergyandastheirmisorientationincreaseswithstrain,thedrivingforceforrecrystallizationwillincrease.随着应变的增加，亚晶界的取向错误增加，再结晶驱动力也增加，因此亚晶界对储存能量的贡献最大。3.1.2StaticRecrystallizationRate应力的增加与应变应呈线性关系，这样，

更多地依赖于应变的t0.5也引起形核处密度和形核率的增加。However,thisincreasewouldbeexpectedtobeaboutlinearwithstrainsothemuchgreaterdependenceoft0.5onstrainmustalsoarisefromanincreaseindensityofnucleationsitesandinnucleationrate.Thelackofinfluenceofstrainratemaythusreflectcompensatingeffectsonstoredenergyandsubstructuredevelopmentatanystrain.Thiscontrastswiththestrainrateeffectobservedforstainlesssteel.应变速率的影响少，这也许体现了在任何应变下，储存能量和亚结构发展的补偿效应。这与应变速率影响了所观察的不锈钢形成对比。3.1.2StaticRecrystallizationRateDjaic和Jonas的研究发现，应变0.8εp是急剧转折点。应变＜0.8εp时，t0.5对应变产生依赖，而应变＞

0.8εp，t0.5的变化不依赖于应变，如图3.4所示。TheobservationofDjaicandJonasindicatethatanabruptchangetakesplacefromstraindependencetoindependenceatastrain~0.8εp,asillustratedinFig3.4.Thiscorrespondsreasonablywiththestrainexpectedforεcandarisesbecausepre-existingrecrystallizationnucleiarealwayspresentinthedeformedstructureatstrainsgreaterthanεc.这很好地对应了临界应变εc，这种现象的出现是由于已有的再结晶形核总是在超过临界应变εc处发生。3.1.2StaticRecrystallizationRate这种条件下产生的静态再结晶作为亚动态，区别于发生在较低的应变下形核在变形后形成的传统再结晶。Staticrecrystallizationundertheseconditionshasbeenreferredtoasmetadynamictodistinguishitfromtheclassicalrecrystallizationafterlowerstrainswhenthenucleimustbeformedafterdeformation.Therestorationmeasurementsindicatethattherecrystallizationkineticsmayhaveacomplexformafterstrainsbetweenεcandtheonsetofsteadystate,anddirectmetallographicobserbationsofstaticrecrystallizationafterstrainswellintosteadystateshowthattheexponentkintheAvramiequationdropstoavalueof-1.回复测试表明，当应变位于εc和稳定态开始之间，再结晶动力学可能有一个复杂形式。应变进入稳定态后，静态再结晶的金相观察表明，阿夫拉米方程中的指数k下降到1左右。3.1.2StaticRecrystallizationRate这意味着，t0.5=0.074t0.5，t0.95=4.33t0.5，即，变形期间提供动态再结晶结构的应变时间内，静态再结晶在两个数量级之后继续发生。Thismeansthatt0.5=0.074t0.5

andt0.95=4.33t0.5,i.e.,staticrecrystallizationproceedsoverabouttwoordersofmagnitudeintimeafterstrainswhichgivedynamicallyrecrystallizedstructuresduringdeformation.3.1.2StaticRecrystallizationRate3.2SubgrainandDislocationStrengtheningWordsandterms:Strengthen强化；defect缺陷；retention保留物；substructure亚结构；yieldstrength屈服强度；Twophaseregion两相区；precipitation沉淀物；microalloyedsteel微合金钢；carbonitride碳氮化物polygonalgrain多边形晶粒；subgrainorcell亚晶粒averageintercept平均截距；lineardependence线性关系3.2SubgrainandDislocationStrengthening由于变形引起的缺陷强化效应早已被人们熟知，这种效应用来提高特别是冷加工处理的金属和合金的强度。Thestrengtheningeffectofdefectsintroducedbydeformationhasbeenappreciatedformanyyears,andithasbeenusedasameansofraisingthestrengthlevelsinmetalsandalloysparticularlybycold-workingtechniques.asameansof，作为一种手段3.2SubgrainandDislocationStrengthening最近人们开始关注通过热加工材料中的亚结构提高强度的研究。Morerecentlyattentionhasbeengiventotheincreaseinstrengththrougharetentionofasubstructureinhot-workedmaterials.Forexample,theextensionofacontrolledrollingscheduletolowertemperatures,inthecaseofmicroalloyedsteels,isknowntoaddasignificantcontributiontotheyieldstrength.例如，将可控压延规程延长至低温，就微合金钢而言，以屈服强度的提高被人们认识。inthecaseof，在…..情况下

3.2SubgrainandDislocationStrengthening由此产生的结构主要是由回复或者再结晶过程的难易程度决定。Thisisusuallybroughtaboutbyrollinginthetwophaseγ+αregionor,atstilllowertemperatures,insingle-phaseferrite.Theresultantstructureislargelydeterminedbythedifficultyorotherwiseofrecoveryorrecrystallizationprocesses.这通常是由γ+α两相区轧制或者低温下单相铁素体引起的。orotherwise，或相反

Inmicroalloyedsteelsthisisusuallyduetocarbidesandnitrides,orcarbonitride.在微合金钢中，通常是由碳化物和氮化物或者碳氮化物引起的。Wheretheaimistoallowacertaindegreeofrecoverytoproceedbutpreventrecrystallization,pinningofsub-boundariesisdeliberatelysoughtthroughprecipitation.其目的是允许一定程度的回复发生，但避免发生再结晶以及析出物中亚晶界的钉扎现象。3.2SubgrainandDislocationStrengtheningTheyieldstrengthisincreasedifasmallferritegrainsize(＜7μm)canberetainedaftercoolingtoroomtemperature.如果将材料冷却到室温，铁素体中的小尺寸晶粒得以保留(＜7μm)，那么屈服强度就将增加。3.2SubgrainandDislocationStrengtheningAusteniteintheformofafinepolygonalgrain(＜20μm)heformof，以……形式

以细小的多边形晶粒(＜20μm)或者变形的拉长结构存在的奥氏体可以转变成小尺寸铁素体晶粒。Severalreviewsofthemechanismsofsubstructuralstrengtheninghavebeenpublishedinrecentyearsinwhichtheavailabletheorieshavebeendiscussedinrelationtothelargevolumeofexperimentwork.近年来关于亚结构强化机制的综述文章较多，文章中讨论了大量实验工作可用的理论。3.2SubgrainandDislocationStrengtheningHowever,relativelylittleconsiderationshavebeengiventolowfinish-rollingtemperaturestructureswhicharenowforexampleconsideredtobeessentialtoobtainthenecessarystrengthinX70gradelinepipesteels.inrelationto，关于，涉及

然而，少有文章考虑低终轧温度下的结构，例如，该结构对于提高X70坡度线管钢的强度有重要意义。FollowingtheHall-Petchanalysesofthegrainsize(d)—yieldstress(σy)dependencetherehavebeenseveralreportsofasimilarapproachbeingadoptedformicrostructurescontainingsubgrainsorcells(averageintercept,l).