ch07-應(yīng)變硬化與退火-E-2

1TheScienceandEngineeringofMaterials,4thed2003

DonaldR.Askeland–PradeepP.PhuléChapter7–StrainHardeningandAnnealing應(yīng)變硬化(加工硬化)與退火2IntroductiontoChapter1Thetetrahedronofmaterialsscienceandengineering

材料科學(xué)與工程四面體3Reviewofknowledge知識(shí)回顧C(jī)hapter1–IntroductiontoMaterialsScienceandEngineering

緒論Chapter2–AtomicStructure原子結(jié)構(gòu)Chapter3–AtomicandIonicArrangements

原子和離子的排列Chapter4–ImperfectionsintheAtomicandIonicArrangements原子和離子排列中的缺陷Chapter5–AtomandIonMovementsinMaterials

材料中原子和離子的運(yùn)動(dòng)Chapter6–MechanicalPropertiesandBehavior

機(jī)械性質(zhì)與行為4

ObjectivesofChapter7第七章目標(biāo)Tolearnhowthestrengthofmetalsandalloysisinfluencedbymechanicalprocessingandheattreatments.學(xué)習(xí)機(jī)械加工和熱處理如何影響金屬和合金的強(qiáng)度。Tolearnhowtoenhancethestrengthofmetalsandalloysusingcoldworking.學(xué)習(xí)如何利用冷加工提高金屬和合金的強(qiáng)度Tolearnhowtoenhanceductilityusingannealingheattreatment.學(xué)習(xí)如何利用退火提高展延性5ChapterOutline本章概要7.1RelationshipofColdWorkingtotheStress-StrainCurve冷加工與應(yīng)力-應(yīng)變曲線(xiàn)的關(guān)聯(lián)7.2

Strain-HardeningMechanisms應(yīng)變硬化的機(jī)理7.3PropertiesversusPercentColdWork（%CW）

性質(zhì)與%CW7.4Microstructure,TextureStrengthening,andResidualStresses微觀(guān)結(jié)構(gòu)，織構(gòu)強(qiáng)化，殘余應(yīng)力7.5CharacteristicsofColdWorking冷加工的特性7.6TheThreeStagesofAnnealing退火的三個(gè)階段7.7ControlofAnnealing退火的控制7.8AnnealingandMaterialsProcessing退火和材料處理7.9HotWorking熱加工7.10SuperplasticForming(SPF)超塑性成型6

Section7.1RelationshipofColdWorkingtotheStress-StrainCurve冷加工與應(yīng)力-應(yīng)變曲線(xiàn)的關(guān)聯(lián)

Strainhardening應(yīng)變硬化Strainhardeningexponent(n)

應(yīng)變硬化指數(shù)（n）7應(yīng)變硬化Strainhardening金屬材料在再結(jié)晶溫度以下塑性變形時(shí)強(qiáng)度和硬度升高，而塑性和韌性降低的現(xiàn)象。又稱(chēng)冷作硬化。產(chǎn)生原因是，金屬在塑性變形時(shí)，晶粒發(fā)生滑移，出現(xiàn)位錯(cuò)的纏結(jié)，使晶粒拉長(zhǎng)、破碎和纖維化，金屬內(nèi)部產(chǎn)生了殘余應(yīng)力等。加工硬化的程度通常用加工后與加工前表面層顯微硬度的比值和硬化層深度來(lái)表示。

加工硬化給金屬件的進(jìn)一步加工帶來(lái)困難。如在冷軋鋼板的過(guò)程中會(huì)愈軋愈硬以致軋不動(dòng)，因而需在加工過(guò)程中安排中間退火，通過(guò)加熱消除其加工硬化。又如在切削加工中使工件表層脆而硬，從而加速刀具磨損、增大切削力等。但有利的一面是，它可提高金屬的強(qiáng)度、硬度和耐磨性，特別是對(duì)于那些不能以熱處理方法提高強(qiáng)度的純金屬和某些合金尤為重要。如冷拉高強(qiáng)度鋼絲和冷卷彈簧等，就是利用冷加工變形來(lái)提高其強(qiáng)度和彈性極限。又如坦克和拖拉機(jī)的履帶、破碎機(jī)的顎板以及鐵路的道岔等也是利用加工硬化來(lái)提高其硬度和耐磨性的。

8Figure7.2Manufacturingprocessesthatmakeuseofcoldworkingaswellashotworking.Commonmetalworkingmethods冷加工及熱加工過(guò)程。普通的金屬加工方式。Forging鍛造Extruding擠壓Drawing拉拔Stamping沖壓Rolling軋制9Strainhardeningexponent(n)應(yīng)變硬化指數(shù)（n）在金屬材料拉伸真應(yīng)力應(yīng)變曲線(xiàn)上的均勻塑性變形階段關(guān)系式：σ

=kεn

（σ：真應(yīng)力，

ε：真應(yīng)變）

應(yīng)變硬化指數(shù)n反映了金屬材料抵抗繼續(xù)塑性變形的能力，是表征金屬材料應(yīng)變硬化的性能指標(biāo)。

在極限情況下，n＝1，表示材料為完全理想的彈性體，σ與ε

成正比關(guān)系；

n＝0時(shí)，σ＝k＝常數(shù)，表示材料沒(méi)有應(yīng)變硬化能力，例如室溫下產(chǎn)生再結(jié)晶的軟金屬及已受強(qiáng)烈應(yīng)變硬化的材料。大多數(shù)金屬的n值在0.1~0.5之間。10?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.3Thetruestress-truestraincurvesformetalswithlargeandsmallstrain-hardeningexponents.Largerdegreesofstrengtheningareobtainedforagivenstrainforthemetalwiththelargern具有大的和小的應(yīng)變硬化指數(shù)（n）的金屬的真應(yīng)力-應(yīng)變曲線(xiàn)，當(dāng)應(yīng)變給定時(shí)，具有較大n的金屬的應(yīng)變硬化程度更大。lnσ=lnK+nlnε11典型金屬和合金的應(yīng)變硬化指數(shù)和強(qiáng)度系數(shù)磅力/英寸2(psi)=psi=磅力/英寸2鈦鉬奧氏體不銹鋼淬火和回火中碳鋼退火合金鋼12Section7.2Strain-HardeningMechanisms應(yīng)變硬化的機(jī)理

Frank-Readsource-Apinneddislocationthat,underanappliedstress,producesadditionaldislocations.Thismechanismisatleastpartlyresponsibleforstrainhardening.弗蘭克-瑞德源–一個(gè)被釘住的位錯(cuò)，在外加應(yīng)力的作用下，引起額外的位錯(cuò)。這一機(jī)制至少是引起應(yīng)變硬化的部分原因。Thermoplastics-Aclassofpolymersthatconsistoflarge,longspaghetti-likemoleculesthatareintertwined(e.g.,polyethylene,nylon,PET,etc.).

熱塑性塑料

–一類(lèi)由長(zhǎng)鏈大分子相互纏繞組成的聚合物（例如，聚乙烯，尼龍，聚對(duì)苯二甲酸乙二酯等。）13Figure7.5TheFrank-Readsourcecangeneratedislocations.(a)Adislocationispinnedatitsendsbylatticedefects.(b)Asthedislocationcontinuestomove,thedislocationbows,eventuallybendingbackonitself.(c)finallythedislocationloopforms,and(d)anewdislocationiscreated.(e)ElectronmicrographofaFrank-Readsource(330,000).弗蘭克-瑞德源能產(chǎn)生位錯(cuò)。(a)一個(gè)位錯(cuò)被它兩端的晶格缺陷固定。(b)當(dāng)位錯(cuò)連續(xù)運(yùn)動(dòng)，該位錯(cuò)變成弓形，最終折回。(c)最后該位錯(cuò)成環(huán)形。(d)形成新的位錯(cuò)。(e)弗蘭克-瑞德源的電鏡照片（330000倍）14?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.6Inanundeformedthermoplasticpolymertensilebar,(a)thepolymerchainsarerandomlyoriented.(b)Whenastressisapplied,aneckdevelopsaschainsbecomealignedlocally.Theneckcontinuestogrowuntilthechainsintheentiregagelengthhavealigned.(c)Thestrengthofthepolymerisincreased在一個(gè)未變形的熱塑性塑料拉力試棒中，(a)聚合物分子鏈?zhǔn)请S機(jī)取向的。(b)當(dāng)施加應(yīng)力后，因分子鏈局部定向排列從而形成細(xì)頸。細(xì)頸增長(zhǎng)直到所有分子鏈定向排列。(c)聚合物的強(qiáng)度被提高。15Section7.3PropertiesversusPercentColdWork性質(zhì)與%CW

percent

coldwork的定義是冷加工前初始橫截面積與冷加工后最終橫截面積的變化百分比，其中包含多個(gè)中間過(guò)程對(duì)結(jié)果沒(méi)有影響。因此總的percent

coldwork實(shí)際上是:%CW=[(t0-tf)/t0]X100%16Section7.3PropertiesversusPercentColdWork性質(zhì)與%CW

?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.7Theeffectofcoldworkonthemechanicalpropertiesofcopper冷加工對(duì)銅的機(jī)械性質(zhì)的影響伸長(zhǎng)率屈服強(qiáng)度抗張強(qiáng)度17Example7.1ColdWorkingaCopperPlate冷加工銅板

A1-cm-thickcopperplateiscold-reducedto0.50cm,andlaterfurtherreducedto0.16cm.Determinethetotalpercentcoldworkandthetensilestrengthofthe0.16-cmplate.(SeeFigure7.8.)

一塊厚度1cm的銅板，被冷加工至0.50cm厚，然后進(jìn)一步冷加工至0.16cm厚。確定0.16cm厚的板材總的%CW和拉伸強(qiáng)度。18?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.8

Diagramshowingtherollingofa1-cmplate(forExample7.1)軋1cm板的示意圖19Example7.1SOLUTION20Example7.2DesignofaColdWorkingProcess設(shè)計(jì)冷加工工藝

Designamanufacturingprocesstoproducea0.1-cm-thickcopperplatehavingatleast65,000psitensilestrength,60,000psiyieldstrength,and5%elongation.設(shè)計(jì)一個(gè)制造工藝生產(chǎn)拉伸強(qiáng)度不低于65,000psi(磅力/英寸2)，屈服強(qiáng)度不低于60,000psi以及斷裂伸長(zhǎng)不低于5%的0.1cm厚度的銅板。Example7.2SOLUTIONToproducetheplate,acold-rollingprocesswouldbeappropriate.TheoriginalthicknessofthecopperplatepriortorollingcanbecalculatedfromEquation7-4.Becausethereisarangeofallowablecoldwork—between40%and45%—thereisarangeofinitialplatethicknesses:要生產(chǎn)這種板材，冷軋工藝是適合的。冷軋之前銅板的初始厚度可通過(guò)%CW計(jì)算。因?yàn)樵试S的%CW在40%~45%范圍內(nèi)（參見(jiàn)圖7-7），初始板材厚度范圍為：21Example7.2SOLUTION(Continued)Toproducethe0.1-cmcopperplate,webeginwitha0.167-to0.182-cmcopperplateinthesoftestpossiblecondition,thencoldrolltheplate40%to45%toachievethe0.1cmthickness.為生產(chǎn)0.1-cm的銅板，我們用盡可能軟的0.167至0.182cm的銅板，冷軋至%CW為40%~45%得到厚度為0.1cm的板材。22Section7.4Microstructure,TextureStrengthening,andResidualStresses微觀(guān)結(jié)構(gòu)，織構(gòu)強(qiáng)化，殘余應(yīng)力

Fibertexture,Sheettexture纖維狀構(gòu)造，薄片狀構(gòu)造Polefigureanalysis,Orientationmicroscopy極圖分析,取向顯微術(shù)Residualstresses,Stress-reliefanneal殘余應(yīng)力，消除應(yīng)力退火Annealingglass,Temperedglass玻璃退火，鋼化玻璃23Figure7.9Thefibrousgrainstructureofalowcarbonsteelproducedbycoldworking:(a)10%coldwork,(b)30%coldwork,(c)60%coldwork,and(d)90%coldwork(250).冷加工得到的低碳鋼纖維狀晶粒結(jié)構(gòu):(a)10%CW，(b)30%CW，(c)60%CW，(d)90%CW(250倍）。24?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.10Anisotropicbehaviorinarolledaluminum-lithiumsheetmaterialusedinaerospaceapplications.Thesketchrelatesthepositionoftensilebarstothemechanicalpropertiesthatareobtained用于航空領(lǐng)域的軋制鋁-鋰薄片的各向異性形為。示意圖所示為拉力試棒的位置與所測(cè)得的機(jī)械性能之間的關(guān)系。屈服強(qiáng)度抗張強(qiáng)度伸長(zhǎng)率25Example7.3DesignofaStampingProcess沖壓過(guò)程的設(shè)計(jì)Onemethodforproducingfansforcoolingautomotiveandtruckenginesistostampthebladesfromcold-rolledsteelsheet,thenattachthebladestoa“spider’’thatholdsthebladesintheproperposition.Anumberoffanblades,allproducedatthesametime,havefailedbytheinitiationandpropagationofafatiguecracktransversetotheaxisoftheblade(Figure7.11).Allotherfanbladesperformsatisfactorily.Provideanexplanationforthefailureofthebladesandredesignthemanufacturingprocesstopreventthesefailures.一種制造用于冷卻汽車(chē)和卡車(chē)發(fā)動(dòng)機(jī)的風(fēng)扇的方式是首先將冷軋鋼板沖壓成葉片，然后將葉片固定在一個(gè)“十字架”上以使得葉片處于適當(dāng)?shù)奈恢?。在同時(shí)生產(chǎn)的葉片中，一定數(shù)量的葉片會(huì)因?yàn)槠诹鸭y的產(chǎn)生和裂紋擴(kuò)展而報(bào)廢，所產(chǎn)生的裂紋與葉片的軸垂直(Figure7.11)

，其它葉片的質(zhì)量則令人滿(mǎn)意。解釋葉片報(bào)廢的原因并重新設(shè)計(jì)制造過(guò)程以防止廢品產(chǎn)生。26?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.11Orientationsofsamples(forExample7.3)試樣的方位Example7.3(continued)軋制方向

想要的

不想要的

27Example7.3SOLUTIONThewrongtypeofsteelmayhavebeenselected.可能選擇了型號(hào)不正確的鋼板。Thediesusedtostampthebladesfromthesheetmaybeworn.由鋼板沖壓葉片所使用的模具可能舊了。Theclearancebetweenthepartsofthediesmaybeincorrect,producingdefectsthatinitiatefatiguefailure.模具各個(gè)部件之間的間隙可能不正確，產(chǎn)生的缺陷引起疲勞破壞。Thefailurescouldalsoberelatedtotheanisotropicbehaviorofthesteelsheetcausedbyrolling.廢品也可能與軋制鋼板時(shí)材料產(chǎn)生的各向異性行為有關(guān)。28?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.12Thecompressiveresidualstressescanbeharmfulorbeneficial.(a)Abendingforceappliesatensilestressonthetopofthebeam.Sincetherearealreadytensileresidualstressesatthetop,theload-carryingcharacteristicsarepoor.(b)Thetopcontainscompressiveresidualstresses.Nowtheload-carryingcharacteristicsareverygoods.殘余壓應(yīng)力可能是有害的或有益的。(a)一個(gè)彎曲力在梁的頂部產(chǎn)生張應(yīng)力。因?yàn)樵陧敳恳呀?jīng)存在殘余張應(yīng)力，承載能力差。(b)頂部存在殘余壓應(yīng)力，承載能力非常好。29Example7.4DesignofaFatigue-ResistantShaft抗疲勞軸的設(shè)計(jì)Yourcompanyhasproducedseveralthousandshaftsthathaveafatiguestrengthof20,000psi.Theshaftsaresubjectedtohigh-bendingloadsduringrotation.Yoursalesengineersreportthatthefirstfewshaftsplacedintoservicefailedinashortperiodoftimebyfatigue.Designaprocessbywhichtheremainingshaftscanbesalvagedbyimprovingtheirfatigueproperties.你的公司生產(chǎn)了數(shù)千根疲勞強(qiáng)度為20,000psi的軸，該軸在轉(zhuǎn)動(dòng)過(guò)程中承受高彎曲載荷。你的經(jīng)銷(xiāo)人員報(bào)告因?yàn)槠谧畛醯膸赘S在短期內(nèi)就損壞了，設(shè)計(jì)處理方法通過(guò)改善軸的疲勞性能來(lái)挽救剩余的軸。30Example7.4SOLUTIONIncreasingthestrengthatthesurfaceimprovesthefatiguelifeoftheshaft–carburizing提高表面強(qiáng)度改善軸的疲勞壽命-滲碳處理Coldworkingtheshaft對(duì)軸進(jìn)行冷加工Shotpeentheshaft軸（表面）噴丸強(qiáng)化噴丸強(qiáng)化分為一般噴丸和應(yīng)力噴丸.一般處理時(shí),鋼板在自由狀態(tài)下,用高速鋼丸打擊鋼板的里面,使其表面產(chǎn)生預(yù)壓應(yīng)力.以減少工作中鋼板表面的拉應(yīng)力,增加使用壽命.應(yīng)力噴丸處理是將鋼板在一定的作用力下的預(yù)先彎曲,然后進(jìn)行噴丸處理.

31Figure7.13Shotpeentheshaft軸（表面）噴丸強(qiáng)化32Section7.5CharacteristicsofColdWorking冷加工的特性

?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.14Acomparisonofstrengtheningcopperby(a)coldworkingand(b)alloyingwithzinc.Notethatcoldworkingproducesgreaterstrengthening,yethaslittleeffectonelectricalconductivity.比較銅的強(qiáng)化效果(a)通過(guò)冷加工強(qiáng)化(b)與鋅形成合金強(qiáng)化。注意冷加工導(dǎo)致更高的強(qiáng)度，但是對(duì)電導(dǎo)率的影響小。屈服強(qiáng)度33?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.15Thewire-drawingprocess.TheforceFdactsonboththeoriginalandfinaldiameters.Thus,thestressproducedinthefinalwireisgreaterthanthatintheoriginal.Ifthewiredidnotstrainhardenduringdrawing,thefinalwirewouldbreakbeforetheoriginalwirewasdrawnthroughthedie.金屬絲-拉拔加工。拉力Fd同時(shí)作用于前后兩種直徑的絲上，因此，作用在最終的絲上的應(yīng)力要高于作用在初始絲上的應(yīng)力，如果在拉拔加工過(guò)程中沒(méi)有出現(xiàn)應(yīng)變硬化，在初始絲被拉出模具之前，最終的絲就將會(huì)斷裂。34Section7.6TheThreeStagesofAnnealing退火的三個(gè)階段Recovery

-Alow-temperatureannealingheattreatmentdesignedtoeliminateresidualstressesintroducedduringdeformationwithoutreducingthestrengthofthecold-workedmaterial.回復(fù)

–退火熱處理低溫階段，作用是消除變形過(guò)程中產(chǎn)生的殘余應(yīng)力，被冷加工的材料強(qiáng)度不降低。Recrystallization-Amedium-temperatureannealingheattreatmentdesignedtoeliminatealloftheeffectsofthestrainhardeningproducedduringcoldworking.再結(jié)晶

-退火熱處理中溫階段，作用是消除冷加工過(guò)程中應(yīng)變硬化效果。Graingrowth

-Movementofgrainboundariesbydiffusioninordertoreducetheamountofgrainboundaryarea.晶粒長(zhǎng)大–因擴(kuò)散導(dǎo)致晶粒邊界移動(dòng)以減少晶粒邊界的面積。35Figure7.16Photomicrographsshowingtheeffectofannealingtemperatureongrainsizeinbrass.Twinboundariescanalsobeobservedinthestructures.(a)Annealedat400oC,(b)annealedat650oC,and(c)annealedat800oC(75).退火處理溫度對(duì)黃銅中晶粒尺寸的影響(a)400oC退火，(b)650oC退火，(c)800oC退火。36?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.17Theeffectofannealingtemperatureonthemicrostructureofcold-workedmetals.(a)cold-worked,(b)afterrecovery,(c)afterrecrystallization,and(d)aftergraingrowth.退火溫度對(duì)冷加工材料微觀(guān)結(jié)構(gòu)的影響。(a)冷加工材料，(b)回復(fù)階段后，(c)再結(jié)晶后，(d)晶粒長(zhǎng)大后。37Section7.7ControlofAnnealing退火的控制

Warmworking-Atermusedtoindicatetheprocessingofmetallicmaterialsinatemperaturerangethatisbetweenthosethatdefinecoldandhotworking(usuallyatemperaturebetween0.3to0.6ofmeltingtemperatureinK).溫加工

–用于表示金屬材料處理的術(shù)語(yǔ)，處理的溫度是介于冷加工和熱加工之間，（以K為溫度單位，通常是在熔點(diǎn)的0.3到0.6倍之間）。38?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.19Longerannealingtimesreducetherecrystallizationtemperature.Notethattherecrystallizationtemperatureisnotafixedtemperature.更長(zhǎng)的退火時(shí)間降低再結(jié)晶溫度。注意再結(jié)晶的溫度不是固定不變的。3940Section7.8AnnealingandMaterialsProcessing退火和材料處理

Heat-affectedzone(HAZ)–Thevolumeofmaterialadjacenttoaweldthatisheatedduringtheweldingprocessabovesomecriticaltemperatureatwhichachangeinthestructure,suchasgraingrowthorrecrystallization,occurs.熱影響區(qū)

(HAZ)–材料鄰近焊接點(diǎn)的區(qū)域，這個(gè)區(qū)域在焊接過(guò)程中受熱超過(guò)了某個(gè)引起材料結(jié)構(gòu)變化的臨界溫度，例如晶粒長(zhǎng)大或再結(jié)晶發(fā)生。41?2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning?isatrademarkusedhereinunderlicense.Figure7.20Thestructu