1-超塑性的研究与发展

金属特种加工理论与技术金属超塑性成形理论与技术（16课时）叶凌英材料加工工程系2015年4月课程内容一、超塑性的研究与发展二、超塑性变形的力学特性三、超塑性变形的组织特性四、组织超塑性变形机理五、金属材料的超塑性参考书目(1)NiehTG,WadsworthJ,SherbyOD.Superplasticityinmetalsandceramics,Cambridge:CambridgeUniversityPress,1997(2)陈浦泉.组织超塑性，哈尔滨，哈尔滨工业大学出版社，1988(3)吴诗惇.金属超塑性变形理论，北京，国防工业出版社，1997(4)文九巴，杨蕴林，杨永顺，陈拂晓，张柯柯，张耀宗.超塑性应用技术，北京，机械工业出版社，2005(5)李云江，特种塑性成形，北京，机械工业出版社，2008一、超塑性的研究与发展内容提要1超塑性的概念2超塑性研究的发展概况3超塑性的分类4超塑性成形的优点与问题5超塑成形应用实例塑性：是金属的重要属性之一，它指的是金属在外力作用下，无损而永久地改变形状的能力[1]。超塑性：（1）金属和合金在特定组织结构和变形温度速度条件下，可以呈现异常高的塑性，延伸率可达百分之几百，甚至达百分之一千或二千以上，变形抗力也很小，这种现象称为超塑性[1]。（2）Superplasticityistheabilityofapolycrystallinematerialtoexhibit,inagenerallyisotropicmanner,veryhightensileelongationspriortofailure[2].（3）超塑性是指材料在拉伸条件下，表现出异常高的伸长率而不产生颈缩与断裂现象。当伸长率大于100%时，即可称为超塑性[3]。一般金属伸长率（δ）均小于100%，如黑色金不大于40%，有色金属不超过60—80%，即使在高温下也难达到100%，而具有超塑性的金属在超塑性条件下δ可达100%以上，变形抗力还很小，如难变形材料Bi-44Sn及Ti-6Al-4V钛合金在超塑性条件下δ值分别为1900%和500%以上，常用铝合金δ达到200-2000%；普碳钢δ为150-200%，滚动轴承刚δ最大值约为500%，流动应力比常规变形的小到几分之一乃到几十分之一。[1]吴诗惇.金属超塑性变形理论，北京，国防工业出版社，1997[2]NiehTG,WadsworthJ,SherbyOD.Superplasticityinmetalsandceramics,Cambridge:CambridgeUniversityPress,1997[3]文九巴，杨蕴林，杨永顺，陈拂晓，张柯柯，张耀宗.超塑性应用技术，北京，机械工业出版社，20051超塑性的概念1超塑性的概念ICSAM：the1991InternationalConferenceonSuperplasticityinAdvancedMaterials(ICSAM-91)heldinOsaka,Japan1超塑性的概念2超塑性研究的发展概况2.1Before1962Ancientarsenicbronzescontainingupto10wt%arsenic,whichwereusedinTurkeyintheearlyBronzeAge,couldhavebeensuperplastic.Thisisbecausethematerialsaretwo-phasealloysthatmayhavedevelopedtherequiredstable,finegrainedstructureduringhand-forgingofintricateshapes.Furthermore,theancientsteelsofDamascus,inusefrom300B.C.tothelatenineteenthcentury,aresimilarincompositiontomodernultrahigh-carbonsteelsthathaverecentlybeendeveloped,inlargepart,fortheirsuperplasticcharacteristics.2超塑性研究的发展概况2.1Before19622超塑性研究的发展概况2.1Before1962In1934,Pearsondramaticallydemonstrated,usingaBi-Snsamplethathadbeendeformedtonearly2000%andthencoiled(asshowninFigure2.4),thatunusuallylargeelongationscouldbeachievedincertainfine-structured,two-phasematerials.Jenkins,forexample,achievedelongationsof300to400%inCd-ZnandPb-Sneutecticsafterthermomechanicalprocessingin1928.2超塑性研究的发展概况2.1Before1962WorkintheSovietUnionwasunderwaytospecificallyaddressthephenomenon,andBochvarandSviderskayacoinedthetermsverhplastichnost(ultrahighplasticity)intheir1945paperonsuperplasticalloys.ApparentlythetermsuperplasticitywasusedforthefirsttimeintheEnglishlanguageinChemicalAbstractsin1947,butfirstappearsina1959technicalpaperbyLozinskyandSimeonovaonthesubjectofSuperhighPlasticityofCommercialIronunderCyclicFluctuationsofTemperature.2超塑性研究的发展概况2.2From1962to1982Althoughpapersonsuperplasticityoccasionallyappearedafter1945,themajorincreaseininterestcamein1962withareviewarticlebyUnderwoodonworkintheSovietUnion.Agraph(Figure2.6)wasincludedinthisreviewthatillustratedtheductilityofZn-Alalloysafterquenchingfrom375℃.Amaximumductilityof650%wasachievedat250℃fora20%Aland80%Znalloy(themonotectoidcomposition).Thisremarkableresult,achievedonasamplethatrequiredonlyaquenchingtreatment.2超塑性研究的发展概况2.2From1962to1982By1968,justfouryearsaftertheBackofendemonstrationofsuperplasticforming,thefirstreviewpaperonthesubjectwaspublishedbyChaudhari,andinthenextyear,thefirstbookentiledSuperplasticityofMetalsandAlloyswaspublishedbyPresnyakov.Afterthat,monographsbyWestern,Soviet,andJapaneseresearcherswerepublished,aswerenumerousreviewarticles.2超塑性研究的发展概况2.3From1982topresentA1982internationalconferenceentitledSuperplasticFormingofStructuralAlloysshowedhowgreattheinterestwasinthesubjectoffine-structuresuperplasticityfrombothacademicandcommercialviewpoints.----Thefeasibilityofthecommercialapplicationofsuperplasticitywasreviewedforalloysbasedontitanium,nickel,aluminum,andiron.ThesecondinternationalconferenceonsuperplasticitywasheldinGrenoble,France,inSeptember1985.ThethirdinternationalconferenceonsuperplasticityinadvancedmaterialswasheldinBlaine,Washington,UnitedStates,inAugust1988.ThefourthinternationalconferenceonsuperplasticitywasheldinOsaka,Japan,inJune1991.ThefifthinternationalconferenceonsuperplasticitywasheldinMoscow,Russia,inMay1994.ChinaandJapanhavebeenheldinBeijingin1985[37]andinYokohamain1986;inthefirstChino-Japanesesymposium,32separatepaperswerepresentedwithconsiderableemphasisplacedonsuperplasticferrous-andaluminumbasedalloys.BoththeChineseandJapanesegovernmentsselectedsuperplasticityin1980forintensenationalresearchanddevelopmentstudies.Theyenvisionsuperplasticity‘asafuturetechnologyintothenextcentury’.2超塑性研究的发展概况2.3From1982topresentTheinitialworldrecordof4850%inaPb-62wt%Snalloywasexceededinacommercialaluminumbronze(Cu-10wt%Al-basedalloy)byavaluereportedfinallyas8000%,asshowninFigure2.9.2超塑性研究的发展概况2.3From1982topresent2超塑性研究的发展概况2.3From1982topresent3超塑性的分类3.1组织超塑性组织超塑性是目前国内外研究最多的一种，一般提到超塑性，就是指这一类超塑性。实现组织超塑性应具备三个条件，即：晶粒度细小；变形温度恒定；应变速率缓慢。（1）晶粒度。材料在变形以前，必须晶粒细化或超细化、等轴化，具有可动的大角度晶界，并且在变形期间晶粒组织具有较好的热稳定性。金属材料一般要求晶粒尺寸小于10µm，陶瓷材料晶粒尺寸需小于1µm，但在个别情况下，如钛合金在粗晶状态下也能有超塑性。等轴化、可动性大角度晶界要求与超塑变形机理有关，因为超塑变形主要靠晶粒间的移动与转动，这就要求有数量多而又短的晶粒边界，只有微细、等轴和大角度晶