Strength evaluation of fine grained steel and microwave sintered ceramics using X-ray diffraction technique

Strength evaluation of fine grained steel and microwave sintered ceramics using X‑ray

diffraction technique

著者 Huang Zhijian

著者別名 黄, 志堅

journal or

publication title

博士学位論文要旨 論文内容の要旨および論文審査 結果の要旨／金沢大学大学院自然科学研究科

volume 平成21年6月

page range 60‑64

year 2009‑06‑01

URL http://hdl.handle.net/2297/26910

黄志堅 博士（工学）

博甲第１０５５号 平成２０年９月２６日

課程博士(学位規則第４条第１項）

StrengthEvaluationofFmeGrainedSteelandMicrowaveSinterec CeramicsUsingX-rayDifficactionlbchnique（Ｘ線回折技術による微細粧 鋼およびマイクロ波焼結したセラミックスの強度評価）

廣瀬幸雄（自然科学研究科・特任教授）

山越憲一（理工研究域・教授)，北川和夫（理工研究域・教授)，

黒堀利夫（人間社会研究域・教授)，佐々木敏彦（人間社会研究域・教授）

氏名 学位の種類 学位記番号 学位授与の日付 学位授与の要件 学位授与の題目

論文審査委員（主査）

論文審査委員（副査）

Abstract

Thisthesisisaimedtoevaluatethestrengthcharacteristicsoffinegrainedsteelandmicrowave sinteredceramics,whichhavesmallergrainsizecomparedtoconventionalsteelandceramics undervariousprocessingconditionsorenvironmentbyusingtheX-raydiffractiontechnique､In thisthesis,X-rayresidualstressmeasurement，asoneofthemostcomnontechniquesthatis

distributioncausedbydirectionalitymechanicalprocessingoffinegrainedsteelwere investigatedwiththetri-axialstressanalysismethodandDebyeringobservation,Thestress corrosionresistancepropertyofthefinegrainedsteelwasalsoevaluatedviaSCC(Stress CorrosionCracking)test・AfterSCCtest,theresidualstressdistributionsinthefracturesurface wereinvestigatedbyX-raydiffractiontechnique・Accordingtotheexperimentresults，fine grainedsteelisshowntohavebetterstresscorrosioncrackingresistancethanconventionalSteeL Ontheaspectofncrowavesinteredceranucs，someadvantagesofmicrowaveheating technologywereconfirmedviathecomparisonoftherateofvolumｅchange,bulkdensity，water absorptionandapparentporosityofmicrowaveandconventionallysinteredsamples､Inaddition，

thehomogeneousperfOrmanceofthemicrowavesinteredceranmcswasevaluatedonthe nncroscopicscalebythethermalresidualstressandtheporeratioinvestigations．Ｉtwas confirmedthatthesinterabilityofceramicsishomogenouslyimprovedbyhybridmicrowave sintering．

論文要旨

Onproductionormanufacturingfields,thedevelopmentoftheproductswhichpossesshigh perfOrmanceusuallyneedhighstrengthmaterials、TherefOre，theimportanceofhighstrength materialshavebeenpaidattentiontobytheresearchersmoreandmore，andavarietyof strengtheningmechanismsｗｅｒｅdeveloped・Grainboundarystrengtheningisoneofthese mechanisms，thismechanismincreasethestrengthviadecreasinggrainsizeofmateriaLA

－６０－

importantmeritofgrainboundarystrengtheningcomparedotherstrengtheningmechanismsis thatitnotonlyimprovethestrengthbutalsoincreasethetoughness・Inaddition,grainboundary strengtheninghasstmfO11owingadvantages:１）increasingstrengthwithoutthechangesof composition;２)ecologyconservationbecauseofmorerecyclabletomaterialsandraremetal saving;３)moreeconomicalcostofmaterialsbecauseofenergyandresourcesavinghthe presentstudyltwotypesofspecialnewmaterials：finegrainedsteelandmicrowavesintered ceramics，whichhavesmallergrainsizecomparedtoconventionalsteelandceramicswere emploiedtoinvestigaｔｅａｎdevaluatetheirstrengthbehavior・

Finegrainedsteelandmicrowavesinteredceramicswouldbeusedonmanyfieldsasnew generation,shighstrengthmaterials・TherefOre，itisnecessarytorealizetheirstrength characteristicundervariousprocessingconditionsorenvironment・Ｗｉｔｈｔｈｉｓａｉｍ,thisthesisis todiscussthestrengthbehaviorsoffinegrainedsteelandmicrowavesinteredceramics materialsafterappropriateprocessingrespectively,viavariousexperimentalmethods．

Inthisthesis,thebehaviorsofresidualstressdistributioncausedbydirectionalitymechanical processingoffinegrainedsteelwereinvestigatedwiththetri-axialstressanalysismethodand Debyeringobservation・Thestresscorrosionresistancepropertyofthefinegrainedsteelwas alsoevaluatedviaSCC(StressCorrosionCracking)testOntheaspectofmicrowavesintered ceramics，someadvantagesofmicrowaveheatingtechnologywereconfirmedviathe comparisonofsomeimportantparametersofmicrowaveandconventionallysinteredsamples・

Inaddition,thehomogeneousperfOrmanceofthemicrowavesinteredceramicswasevaluated onthemicroscopicscale．

Thethesisconsistsof7chapters，andtheimportantcontentsandresultsofeachchapterare

summarizedasfO11ows：

Chapterlisthegeneralintroductionofthisthesis､hthischapter,background,objectivesand contentsofthethesisaremtroducedbrieflyd

InChapter2,X-rayresidualstressmeasurement,asoneofthemostcommontechniquesthatis

usedtomeasureresidualstressesisintroducedindetaiL

TheresidualstressmeasurementsusingX-raydiffractiontechniqueisconsideredas nondestructivemethodThismethodbasicallymeasurestheanglesatwhichthemaximum diffractedintensitytakeplacewhenaCrystallinesampleissubjectedtox-rays・Fromthese angles,itispossibletoobtaintheinterplanarspacingofthediffractionplanesusingBragg,slaw，

whichcanbeexpressedasn形2C/Sinaandtheinterplanarspacingisusedasastraingage・If theresidualstressesexistwithinthesample，thentheresidualstressescausechangesinthe spacingofthelatticeplanesfromtheirstressfreevaluetoanewvaluethatcorrespondstothe magnitudeoftheresidualstresses．

ThefUndamentalequationthatisusedinx-raydiffTactionstrainmeasurementcanbe expressedas

－６１－

(ど'3ルー`/,’'一ａｂ

_ａｂ

+B33cos2u＋e13cos②sin2V,＋823sinのＳｍ”（7-1）

Asaresultofx-raydiffraction,thcrearcthrecbasicbchaviorsof恥vs､sinzufOrad-spacing atall妙tilts，andtheyarelinearbehavior，リーsplittingbehaviorandoscillatorybehavior respectively・ForbothlinearbehaviorandVﾉｰsplittingbehavior,equation7-1canbeusedto detern血ethestrainsfromthegivendata,thencalculatingresidualstressesvalue,However,the dataofoscmatorybehaviorcannotbesolvedwiththeequation7-1．

InChapter3,fOrclarifyingtheinfluenceontheresidualstressdistributionofthedirectionality processingmethoｄａｎｄｔｈｅｇｒａｉｎｓｉｚｅ，specimensoffinegrainedsteelandconventionalsteel wereprocessedbymechanicalgrindingandemerypolishingrespectively､Thenthebehaviorsof residualstressdistributionwereinvestigatedbyX-raydiffractiontechniquewiththetri-axial stressanalysiｓｍｅｔｈｏｄＡｔｔｈｅｓａｍｅｔｉｍｅ，Debyeringobservationwascarriedout，andthe resultswerecomparedwiththoseoftri-axialstressanalysis．

Themainresultsaresummari7zedasfO11ows：

(1)nwasconfirmedbytheobservationofPimagesthatthegrainsizeoffinegramedsteelis biggerthanthatofconventionalsteeL

(2)ＩｎｂｏｔｈＮＦＧ６００ａｎｄＳＭ４９０,thcTri-axialstressstateiscausedbythedirectionality

process1ng．

(3)Inthecaseofmechanicalgrmding,itwasconfirmedthatthemaximumdeptllofthe processinginfluenceofNFG600isbiggerthanthatofSM49０．

(4)Itwasshownthatthedisappearanceofo13ando23correspondedtothechangesoftheIP images,Accordmgtothisresmt,itispossibletoconnectthefirstkindstresswiththethird kindstressbyusingIPimages．

(5)Itisconsideredthatthemaximumdepthoftheprocessinginfluenceisbiggerthanthe settlingpointofTri-axialstress．

ｌｎＣｈａｐｔｅｒ４，fOrabetterunderstandingofthestrengthcharacteristicandenvironmental characteristicoffinegramedsteelundercorrosionenvironment，ＳＣＣｔｅｓｔｗａｓｃａｒｒｉｅｄｏｕｔ・

Subsequently，fracturesurfacewasobservedwithSEMimagesandtheresidualstress distributionsinthefracturesurfacewereinvestigatedbyX-raydiffractiontechnique・The differenceofstresscorrosionresistancepropertybetweenfinegrainsteelandconventionalsteel

wasevaluated

ThemainresultsaresummarizedasfO11ows：

(1)

FinegrainedsteelNFG600isshowntohavebetterstresscorrosioncrackingresistance

－６２－

OnbothNFG600fracturesurfaceandSM490fracturesurface，thecoexistenceof

fracturcductilityandthefOrmofembrittlementisfOrmed・However,SM490causesthe fractureductilitymoreeasilythanNFG600TherefOre,itispossiblethatthecracksize isrelatedtothegrainsizeofthemateriaL

Thedifferenceofplasticzonesizemyduetothedifferenceofthecrystalgrainsizewas confirmedのyofNFG600issmallerthanのyofSM490becausefinegrainsteelNFG600 hasstrongeryieldstrength．

(2)

(3)

hChapter5,fbrconfirmingtheadvantagesofmicrowaveheating,somespecimensofAl203 ceranucsaresinteredundervarioussinteringtemperaturesbyaconventionalheatingmethod andahybridmicrowaveheatmgtechnique・Theheatingvelocityofmicrowaveandconventional methods,therateofvolumechange,bulkdensity,waterabsorptionandapparentporosityofthe conventionallyandmicrowavesinteredsampleswereinvestigated,andtheexperimentalresmts oftwokindsampleswerecompared．

ThefOmowingconclusionscanbemadeviathecomparisonsoftheexperimentalresultsoftwo kindsamples．

(1)Microwavesintermgmethodhasthecharacteristicofrapidheatingcomparedto

conventionalmethod．

（２）Thesinterabnityofhybridmicrowavesinteredsampleisbettertllanthatof conventionallysinteredsampleatthesamesmtermgtemperature．

(3)Microwavesinteringmethodcanreducedthesinteringtemperatureofceramicsｗｈｅｎ comparewitllconventionalmethod．

ＩｎＣｈａｐｔｅｒ６,toevaluatethehomogeneousperfOrmanceofthemicrowavesinteredceranncs，

A1203ceramicsspecimensaresinteredbyhybridmicrowaveandconventionalsmteringmethod，

respectively・Thebehaviorsofthermalresidualstressandtheporeratioswereinvestigated,and utilizedtocharacterizehybridncrowavesinteredspecimensandconventionallysintered specnnens・Thecharacteristicsoftwo-directionalhybridmicrowavesinteringwerealso confirmedbyusingthennalresidualstressandtheporcratiodistributionOtherwise，the VickersHardness(HV)distributionwasalsoinvestigated・TheadvantagesoftheperfOrmance ofhybridmicrowavesinteredceramicsareevaluatedonanncroscopicscale．

ThefOllowingconclusionscanbemade：

(1)Acorrelationbetweenthethermalresidualstressandtheporeratiointhecomposite ceramicmaterialisconfirmed，ａｎｄｉｔｉｓｐｏｓｓｉｂｌｅｔｏｅｖａｌｕａｔｅｔｈｅｓｉnterabilityofceramics

fromthermalresidualstressmeasurements．

(2)TheunifOrmheatingpropertyoftwo-directionalhybridmicrowavesinteringisconfirmed bythethermalresidualstressandtheporeratioinvestigationsonamicroscopicscale．

－６３－

(3)Itisconfirmedthatsinterabilityofceramicsisimprovedbyhybridmicrowaveheating，

andVickershardnesstestsonmicrowavesinteredspecimensrevealedsuperior mechanicalpropertiescomparedtoconventionallysinteredspecimens．

FinallyltheconclusionsobtainedthroughthesestudiesaresummarizedinChapter7．

Asmentionedabove,tmsthesisevaluatesthestrengthcharacteristicsoffinegramedsteeland nncrowavesinteredceramicsundervariousprocessingconditionsorenvironmentbyusingthe X-raydiffractiontechnique・Theresultsobtainedmthisstudyareexpectedtobecontributiveto promotmgthestudyonfinegrainedsteelandmicrowavesinteredceramics．

学位論文審査結果の要旨

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