DOC《匕匕论文题目低碳低合金钢的组织夕》

thehardness ofboththecarburizedlayerandtheeenierdecreased.Theseehangesare hannfullforthePerformaneesofthegearsandearburizedcomPonenis. (3)TheTEMresultsofZoMnCrsgearsa哪lesshowedthatthere were芳Fe5C:carbideswithrelativelylargedimensionsdisPersedinthe microstrue加reoftheoriginalSamPle.Acieularearbideswithsmall中南大学硕士学位论文ABSTRACT dimensionwereformedinthesamPleheatedat350oC/20minforthree times.InthesamPleheatedat500oC/20minforthreetimes,orthrombie 0一Fe3CcarbidesthatkePteertainorientationrelationshiP(OR)witha一Fe formed.Thoughwithsmalldimension,theo一Fe3Cearbidesstartedto sPheroidize. (4)Amethodforfitting{011}. Polefiguresofmartensitefrom EBSDresultswasdesigned.Byfittingthe{011}. Polefiguresof m叭ensitein20MxzCrsand20CrNlnTisteel, theORofmartensitewith itsPrioraustenitegrainwasProvedtofollowbothK-SandN-WORs, andPredominantlyN一WOR.ThiswasfurtherProvedbythediscrePancy betweenPraetiealandtheoretiealmisorieniationdistribution.The diserePancywaseXPlainedbystrainaeeommodationmeehanism.Akind of(011)/54.70lathbounda以whieheanonlybeformedbyadjaeeniK一S ORlathandN一WORlath, wasProvedtoexistinZOMllCrssteel martensite.ThisresultalsoProvedtheeoexisteneeofK一5ORandN一W ORinthemartensite. (5)TheerystallograP坤oftemPeredmartensiteinZOMnCrssteel heatedat350oC/20minandS000C/20minwereexaminedbyEBSD.The resultsProvedthatthegrayscaleoftheimagequalitymaPdeereased, whiehindieatedthatthedensityofdefectsandtheextentofdistortion deereased.Thelengthofgrainboundarieswithdifferenimisorieniationin thescannedareaoftheSamPlesdeereasedwiththeincreaseoftimeand temPerature.IntheseannedareaoftheheatedsamPlesbothofZOMnCrs and20CrNlhTIsteel, theorientationofmartensitedistributedrandomly. ByseleetingonePrioraustenitegrainineaehoftheorientationimage maPs, the{011}Polefiguresweredrawnandfitted.Theresultsshowed thattheORsofmartensiteintheselectedareasallfollowedthe coexisteneeofK一5andN一WORs, blltwithsomevariantsabseni.The heattreatmeniwithhighertemPeraturecausedtheorieniationof martensitegrainsrotatedtosomeexteni, whichcausedmostareasinthe heatedsamPlesdonotfollowK一5andN一WORaeeuratly. KEYWORDS:20MnCrssteel, 20CrMllTisteel,martensi........