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20220102Vol.20No.2TheChineseJournalofNonferrousMetalsFeb.20101004-0609(2010)02-0195-07ZrCrPrAl-Zn-Mg-Cu(410083)Al-Zn-Mg-Cu-ZrAl-Zn-Mg-Cu-Cr-PrAl-Zn-Mg-Cu-Zr-Cr-Pr3ZrCrPrAl-Zn-Mg-CuZrCrPrAl-Zn-Mg-CuZrZrCrPrKC23.3MPa·m1/229.3MPa·m1/2KSCC10.9MPa·m1/224.5MPa·m1/2Al-Zn-Mg-CuPrTG146.4AEffectsofZr,CrandPradditionsonmicrostructureandpropertiesofAl-Zn-Mg-CualloysCHENKang-hua,FANGHua-chan,CHENXiang(InstituteofPowderMetallurgy,CentralSouthUniversity,Changsha410083,China)Abstract:ThreekindsofalloysAl-Zr-Mg-Cu-Zr,Al-Zn-Mg-Cu-Cr-PrandAl-Zn-Mg-Cu-Zr-Cr-Prwerepreparedbycastmetallurgy.TheeffectsofZr,CrandPradditionsonthemicrostructureandpropertiesofAl-Zn-Mg-Cualloyswereinvestigatedbyopticalmicroscopy,scanningelectronmicroscopy,transmissionelectronmicroscopy,tensiletest,polarizationcurvemeasurement,stresscorrosionandexfoliationcorrosiontest.TheresultsshowthatthecombinedadditionsofZr,CrandPrtotheAl-Zn-Mg-Cualloyseffectivelyretardthemergenceandgrowthofthesub-grainduringtherecoveryprocess,significantlyinhibitstherecrystallizationofAlmatrix,thusenhancestheresistancetostresscorrosionandexfoliationcorrosion.ComparedwiththeAl-Zn-Mg-CualloyaddedwithZr,thecomplexadditionsofZr,CrandPrintotheAl-Zn-Mg-Cualloyremarkablyincreasethefracturetoughness(KC)from23.3MPa·m1/2to29.3MPa·m1/2,andenhancetheresistancetostresscorrosioncracking(KSCC)from10.9MPa·m1/2to24.5MPa·m1/2,yieldstrengthandelongationofthealloysallincreasealittle.Keywords:Al-Zn-Mg-Cualloys;microstructure;praseodymium;mechanicalproperties;corrosionpropertiesAl-Zn-Mg-Cu[1−2][3−9]Al-Zn-Mg-CuCrMnZrCrMnL12Al3Zr(2005CB623704)(50721003)(50471057)2009-03-012009-09-020731-88830714E-mail:khchen@mail.csu.edu.cn20102196[10−11]Al3ZrZr[12]Al3ZrDO23Al3Zr[13]2060ScAl3Sc[14−16]ZrAl3ScAl3(Sc,Zr)[17-19]ScZr,ScSc[20]ErAl3ErCeCr2Al20(a=(1.270.05)nmFd3m)[21][22]Al-Zn-Mg-CuZrCrYbCeCr2Al20ZrYbCr2Al20Al-Zn-Mg-CuZrCrLaZrLaCr2Al20[23]PrYbLaZrCrPrAl-Zn-Mg-Cu11(99.9%)(99.9%)Zn(99.9%)CuZrCrPr700~74045mm220~24046524h500t12.24501h4701h4802hT6(13024h)1Table1Nominalcompositionsofaluminumalloys(massfraction,%)AlloyZnMgCuZrCrPrAlA8.62.52.20.16−−Bal.B8.62.52.2−0.100.14Bal.C8.62.52.20.160.100.14Bal.(1׃3)GB228−87CSS−44100()CHI600C5.7%NaCl+1%H2O2()(DCB)GB/T12445.11990(LT)3.5%NaCl(351)aKI231/2I32[3(0.6)]4[(0.6)]EVhhlhhKlhhl++=++(1)VmmEGPahmmlmmKMPa·m1/2HB5455−90NaCl234g/LKNO350g/LHNO36.5mg/L48h(251)30%HB5455−90NPEA~EDEAEBECEDEC202ZrCrPrAl-Zn-Mg-Cu19722.111(a)(c)(e)1(a)(c)(e)CrPrBZrAZrCrPrC1(b)(d)(f)1(b)(d)(f)ABCZrCrPrAl-Zn-Mg-Cu2.22ZrCrPrAl-Zn-Mg-CuT6TEM2(a)EDXCrPrZrAl20~50nm2.32AC6%10%BC1Fig.1Opticalmicrostructuresofalloysbyelectro-polishedandanodizedandgraff-sargentreagentetched:Electro-polishedandanodized,alloyA(a),alloyB(b)alloyC(e);Graff-sargentreagentetched,alloyA(b),alloyD(d),alloyC(f)201021982CT6TEMEDSFig.2TEMimages((a),(b))andEDSpattern(c)offinesphericaldispersoidsinT6-temperedalloyC41MPa8%10%CS-L29.3MPa·m1/2A(23.3MPa·m1/2)B(22.3MPa·m1/2)33SEM3ABCZrCrPrZrCrPrAl-Zn-Mg-Cu2Table2TensilepropertiesandfracturetoughnessoftestedalloysAlloyσb/MPaσ0.2/MPaδ10/%KC(S-L)/(MPa·m1/2)A704.0693.86.023.3B674.7669.28.022.3C716.3706.010.029.33SEMFig.3FracturalSEMimagesofalloysA(a),B(b)andC(c)2.42.4.1434ZrCrPr202ZrCrPrAl-Zn-Mg-Cu199ZrACrPrBAKSCC10.9MPa·m1/2BKSCC12.8MPa·m1/2ZrCrPrCKSCC24.5MPa·m1/22.4.2HB5455−9048h55348hBABCA4Fig.4RelationshipsbetweenstresscorrosioncrackgrowthratevandstressintensityfactorKofalloys5EXCO48hSEMOMFig.5SEMimagesofsurfacesofalloysA(a),B(c)andC(e)andOMimagesofcross-sectionofalloysA(b),B(d)andC(f)afterimmersed48hinEXCOsolution20102200BBAC48hABCEB+EDEAZrCrPrAl-Zn-Mg-Cu2.4.36363ABCZrCrPrAl-Zn-Mg-Cu3Table3CorrosionparametersofpolarizationcurvesofalloysAlloyφcorr/VJcorr/(10−4A·cm−2)Rp/(Ω·cm2)A−0.6697.4687.468B−0.6834.4714.471C−0.6634.3154.3156Fig.6Potentiodynamicpolarizationcurvesofalloys31CrPrZrZrCrPrZrPrCr2Al20Al-Zn-Mg-CuPrCr2Al20Al3ZrZrPrCr2Al20Al-Zn-Mg-CuZrCrPrAl-Zn-Mg-CuZrPrCr2Al20Al-Zn-Mg-Cu()()()Al-Zn-Mg-CuZrCrPrZrCrPr41)ZrCrPrZrPrCr2Al20Al-Zn-Mg-Cu2)ZrCrPrZrCrPrAl-Zn-Mg-CuAl-Zn-Mg-Cu-ZrAl-Zn-Mg-Cu-Cr-PrAl-Zn-Mg-Cu-Zr-Cr-PrS-LKC23.322.329.3MPa·m1/23)ZrCrPr202ZrCrPrAl-Zn-Mg-Cu201ZrCrPrAl-Zn-Mg-CuAl-Zn-Mg-Cu-ZrKSCC10.9MPa·m1/2EB+Al-Zn-Mg-Cu-Cr-PrKSCC12.8MPa·m1/2EDAl-Zn-Mg-Cu-Zr-Cr-PrKSCC24.5MPa·m1/2EA4)ZrCrPrZrCrPrAl-Zn-Mg-CuREFERENCES[1]DIXITM,MISHRARS,SANKARANKK.Structure-propertycorrelationsinAl7050andAl7055high-strengthaluminumalloys[J].MaterSciEngA,2008,478(1/2):163−172.[2]DUMONTD,DESCHAMPSA,BRECHETY.Ontherelationshipbetweenmicrostructure,strengthandtoughnessinAA7050aluminumalloy[J].MaterSciEngA,2003,356(1/2):326−336.[3]CHENKang-hua,LIUHong-wei,ZHANGZhuo.Theimprovementofconstituentdissolutionandmechanicalpropertiesof7055aluminumalloybysteppedheattreatments[J].JournalofMaterialsProcessingTechnology,2003,142(1):190−196.[4]REDAY,KARIMRA,ELMAHALLAWII.ImprovementsinmechanicalandstresscorrosioncrackingpropertiesinAl-alloy7075viaretrogressionandreaging[J].MaterSciEngA,2008,(1/2):468−475.[5]BUHAJ,LUMLEYRN,CROSKYAG.Secondaryageinginanaluminiumalloy7050[J].MaterSciEngA,2008,492(1/2):1−10.[6]FENGChun,LIUZhi-yi,NINGA