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《電參數(shù)對鎂合金微弧氧化膜層的顯微結(jié)構(gòu)和耐蝕性能的影響》由會員上傳分享，免費在線閱讀，更多相關(guān)內(nèi)容在學(xué)術(shù)論文-天天文庫。
1、華中科技大學(xué)碩士學(xué)位論文電參數(shù)對鎂合金微弧氧化膜層的顯微結(jié)構(gòu)和耐蝕性能的影響姓名：劉全心申請學(xué)位級別：碩士專業(yè)：材料加工工程指導(dǎo)教師：蔡啟舟20050401華中科技大學(xué)碩士學(xué)位論文摘要鎂合金微弧氧化技術(shù)是通過電解液中高壓放電作用使鎂合金表面形成硬質(zhì)陶瓷層的一種新工藝所形成的陶瓷膜層具有硬度高絕緣性和耐蝕性好與基體結(jié)合力強的優(yōu)點是一種極具發(fā)展前途的鎂合金表面處理技術(shù)本文利用自主開發(fā)的微弧氧化專用電源對置于(NaPO3)6溶液中的AZ91D鎂合金進行微弧氧化處理研究了電流電壓頻率占空比和波形等電參數(shù)對膜層的顯微結(jié)構(gòu)和耐蝕性能的影響規(guī)律試驗結(jié)果表明微弧氧化處理過程中電壓電流呈規(guī)律性的變化
2、當(dāng)電壓電流和占空比增大時膜層的增厚速度增大相應(yīng)地表面粗糙度增大孔隙率也增大而當(dāng)頻率增大時膜層的增厚速度減小表面更光滑孔隙率減小通過微弧氧化形成陶瓷膜層后鎂合金的耐蝕性能得到顯著改善借助金相顯微鏡和SEM觀察了膜層表面和斷面的形貌用能譜儀和XRD研究了膜層的成分組成(NaPO3)6溶液中鎂合金微弧氧化膜層由外層疏松層和內(nèi)層致密層組成內(nèi)層致密層與基體之間為冶金結(jié)合外層疏松層存在許多放電微孔陶瓷膜相組成的主要為MgOMgAl2O4Mg3(PO4)2關(guān)鍵詞鎂合金微弧氧化電參數(shù)顯微結(jié)構(gòu)耐蝕性能I華中科技大學(xué)碩士學(xué)位論文AbstractMicroarcoxidation(MAO)ofmagne
3、siumalloysisaplasmadischargethatoccursatthemetal/electrolyteinterfacewhentheappliedvoltageexceedsacertaincriticalbreakdownvalue.Theprocessproducesthick,hardandwell-adheredceramic-likecoatingstobeobtainedwithhighcorrosionresistance,thermalstabilityanddielectricproperties.Therefore,MAOisoneofthe
4、mostprospectivemethodsofsurfacetreatmentformagnesiumanditsalloys.Inthisinvestigation,theMAOprocessingonmagnesiumalloyAZ91Din(NaPO3)6aqueoussolutionwascarriedoutbyusingofthepowersupplymanufacturedwithourowndesign.Theeffectofpulseparameters(voltageorcurrent,frequencyanddutycycle)onmicrostructure
5、andcorrosionresistancewasinvestigated.Theexperimentalresultsshowthat,thevoltageandcurrentchangeregularly.Thegrowingrateofcoatingsincreaseswiththeelevatingofvoltage,currentanddutycycle.Accordingly,coatingsurfacebecomesrougherandthepercentofporeincreases,aswell.But,whenfrequencyincreases,thegrow
6、ingrateofcoatingsreduces,thesurfacebecomessmootherandthepercentofporedecreases.Theceramic-likecoatingsformedduringMAOprocessingcanenhancethecorrosionresistanceofAZ91Dalloysignificantly.Thecoatingmicrostructureandmorphologywerecharacterizedbyopticalandscanningelectronmicroscopy,observingthestru
7、cturebothparalleltothesubstrateandalsoinpolishedcross-sections.PhasecompositionwasstudiedbyXRDanalysis.Thecoatingsformedin(NaPO3)6aqueoussolutioncontainedtwolayers:anouterlooselayer,whichhasalotofsmallpores,andaninnercompactlayer,whichg
