低碳钢表面纳米化组织结构及性能研究

太原理工大学硕士学位论文低碳钢表面纳米化组织结构及性能研究姓名：史美霞申请学位级别：硕士专业：@指导教师：卫英慧@I(SDP)SNC-1Q235X(XRD)(TEM)(SEM)(1)(2)(3)10~20nm90120min3060minII90min90min55NIIIINVESTIGATIONOFMICROSTRUCTUREANDPROPERTYOFTHELOWCARBONSTEELAFTERNANOCRYSTALLIZATIONAbstractMostfailuresofmaterialsoccuronsurface,includingfatiguefracture,corrosionandwearetc.,whichareverysensitivetomicrostructureandpropertiesofthesurface.Asaresult,thesurfacemodificationofengineeringmaterialsisfoundtoprocessmoreandmoreindustrialapplications.Surfacenanocrystallizationisanewconceptproposedinrecentyears.Itusesmethodssuchassevereplasticdeformation(SPD)togenerateananostructuredsurfacelayer,whichcanimprovetheoverallpropertiesandbehaviorsofmaterials.Inthisarticle,ananostructuredsurface1ayerwasfabricatedonthelowcarbonsteelbymeansofsurfaceshotpeeningtreatment.Byusingopticalmicroscopy,X-raydiffraction(XRD),transmissionelectronicmicroscopy(TEM),scanningelectronicmicroscope(SEM),microhardnesstestingmachinetoinvestigate:(1)thelayersofsevereplasticdeformationwithnanocrystallinestructuresweregottenonlowcarbonsteelaftershotpeeningtreatment;(2)effectonpropertiesoflowcarbonsteelaftershotpeeningtreatment;(3)effectonfrictionandwearpropertiesoflowcarbonsteelbymeansofsurfacenanocrystallization.InthelastparttheanomalousresponseoflowcarbonsteelplateduringsurfacenanocrystallizationisstudiedusingFiniteElementAnalysismethod.Andhowthethicknessofthetestsampleandimpactloadaffectstheanomalousresponseisstudied.Afterthesurfaceshotpeeningtreatment,ananocrystallizationsurfacelayerIVwasformed,theaveragegrainsizeofwhichis20-30nm,andthegrainsizeincreaseswiththeincreaseofdepthstothesurface.Themicrohardnessofnanostructuredsurfaceisenhancedsignificantlyaftertheshotpeeningtreatmentcomparedwiththatoftheoriginalsample.Baseonthecomparisonofthemicrohardness,surfaceroughnessandcorrosionofthesample,theresultsthatthebesttimeofnanocrystallizationforlowcarbonsteelis90minisgiven.Afternanocrystallizationthewearresistanceoflowcarbonsteelinlowandmediumloadisimproved.Andthefrictioncoefficientisreducedsignificantly.Whentheloadincreasesto55N,thewearresistancedecreasedslightlycomparedwiththeoriginalsample.Astheloadincreases,themainwearmechanismchangesfromabrasiveweartofatiguewear.Surfacenanocrystallizationhelpsweakenthefatigueweareffectoflowcarbonsteel.ThepossibilitythattheanomalousresponseoflowcarbonsteelplatecouldappearduringSurfacenanocrystallizationprocessusingSMATmethodisprovedbythefiniteelementanalysisresults.KEYWORDSlowcarbonsteel,surfacenanocrystallization,shotpeening,microhardness,frictionandwear,anomalousresponse11.1[1~3][4][6][7]SurfaceNanocrystallizationSNCSSNC[5][8]21.21.2.1H.Gleiter100nm1231~100nm[9]1234[10]1.2.23PECVDLICVD[11][12][13]1.MechanicalmillingMM[14]1.1[10]1-1[10]Fig.1-1AschematicillustrationofthetechniqueofmechanicalmillingFecht[15]0.5~1nm4O2N2H2O[11]2.EqualchannelangularpressingSegal[16]20mm70mm100mm0º90º180º1-21-2[16]Fig.1-2Aschematicillustrationofthetechniqueofequalchannelangularpressing200~300nm5[11]3UltrasonicshotpeeningUSSP[17]1-31-3USSP[17]Fig.1-3SchematicillustrationoftheUSSP[18]4.CrystallizationofAmorphousMaterialsCAMCAM[19-20]61.2.32000[21-24]1.2.3.[8][26][25]71.31.410~50µm[17]1-4[26]Fig.1-4Schematicillustrationofmicrostructureinthesurfacelayersubjectedtothesurfacenanocrystallization1.3.1[27]110~50µm81-5(a)PVDCVD1-5[7](a)(b)(c)Fig.1-5Schematicillustrationofthreetypesofsurfacenanocrystallizationprocesses(a)Surfacecoatingordeposition;(b)Surfaceself-nanocrystallization;(c)Hybridsufacenanocrystallization21-5(b)9SMAT[17][28][29][30]31-5(c)[31][32]1.3.2[21]1-6101-6[32]Fig.1-6SchematicillustrationofthesurfacemechanicalattritiontreatmentU1-7[27]1-81-7[12]Fig.1-7Plasticdeformationingrainofmaterialssurfacebytheimpactingoftheshot1-8[17]Fig.1-8ThelocalizedplasticonthesurfacelayerbytheimpactingoftheshotSample11[33][32]1.4121.4.1[21]1.Hall-Petch[8]21−+=kdoσσ1-1oσkd[8]2.[34][35]131.4.3[36-38][39]Cr-Z0.05H2SO4+0.05Na2SO4[40]35nm35nm[41]1.514SMATQ235X15[1]Hsien-Chun,MengAntonioBalaguer,YauShyu,etc.NanostructuredMaterials,Thematerialsforthe21stcentury[J].ScienceandTechnologyInformationCenterNationalScienceCouncil,ChineseTaipei[2].[J].200131(1)47-61[3].[J].2000(6)43-46[4].40Cr[D].2005[5]H.Gleiter,N.Hansen,T.Leffersand.InternationalSymposiumonMetallurgyandMaterialsSciences[J].LilholtRoskilde,1981:15-20[6]./[J].200707(03)60-61[7].()[J].200603(1)56-60[8].()[J].200603(2)51-56[9]GleiterH.Nanocrystallinematerials[J].ProgMaterSci,1989,33(4):223-315[10].316L[D].2002[11].[D].2005[12].[J].2001(3)1-6[13].[J].200238(2)157-160[14].[J].20003300-303[15]FechtHJ.NanophasematerialsbymechanicalattritionsynthesisandcharacterizationNanophaseMaterials[J].KluwerAcademicPublishers,1994,6:125-129[16]SegalVM,ReznikovVI,PavlikDA,etc.ProcessesofplasticTransformationofmetals[J].NavukaTeknika,1984,38:295-300[17]LuK.andLuJ.Surfacenanocrystallization(SNC)ofmetallicmaterials-presentationof16theconceptbehindanewapproach[J].Mater.SciTechnol.1999,15(3):193-197[18].7A04[D].2006[19]K.Lu,J.T.Wang,WDWei.Anewmethodforsynthesizingnanocrystallinealloys[J].A