泡沫镁的制备工艺及压缩性能研究(1)

河北工业大学硕士学位论文泡沫镁的制备工艺及压缩性能研究姓名：黄春瑛申请学位级别：硕士专业：材料加工工程指导教师：赵维民201004017207wt%500r/min3min7402.5wt%1000r/min0.5min7405min43.7~90.08%0.7~3.5mm270MPa400440MPa30s2.5wt.%7405min12.3~38%1.2~2.2mmCOSTUDYONFABRICATIONPROCESSANDCOMPRESSIVEPROPERTYOFMAGNESIUMFOAMABSTRACTMagnesiumandmagnesiumalloyfoamhasgooddampingpropertiy,impactresistance,electromagneticshieldingproperty,acousticabsorptionandbiocompatibilitycanbeapplictedintheautomotive,aerospaceandaircraftindusties,constructionandmedicalfields.Inthispaper,magnesiumfoamswerefabricatedbymeltfoamingandpowdermetallurgy.Theinfluenceofprocessingparametersonfoamingeffect,foamingmechanicsandcompressivepropertieswerealsodiscussed.Formeltfoamingmethod,theeffectsofadditivesize,contentandaddingtemperature,foamingtemperatureandholdingtimeontheporosityandstructurewereinvestigated.Theresultsshowthat:adding7wt.%contentsofviscosifertomagnesiummeltat720,mixingfor3minat500rpm;adding2.5wt.%contentsofblowingagenttomagnesiummeltat740,mixingfor0.5minat1000rpm;holdingthemoltenfor5minandwatercooling,magnesiumfoamswithwellstructure,porositywithin43.7~90.08%andaverageporesizewithin0.7~3.5mmcouldbefabricated.Inaddition,thereasonsandimprovementmeasuresfordefectssuchasfree-bubblelayer,localbighole,crackandoxidizingslagwerealsodiscussed.Forpowdermetallurgymethod,theeffectsofpressingmethod,pressingforce,blowingagentcontentandfoamingtemperatureonfoamingefficiencywerestudied.Theresultsshowthat:pressingthepowderunderapressureof270MPa,thenpressingagainat440MPaat400hightemperature,dwellingfor20s;adding2.5wt.%contentofblowingagent,foamingat740andafterholdingfor5minthenwatercoolingtheprecursor,magnesiumfoamswithwellstructure,porositywithin12.3~38%andaverageporesizewithin1.2~2.2mmcouldbefabricated.Inaddition,thereasonandimprovementmeasuresfordefectssuchaslocalbigholeandcrackwerealsodiscussed.Foamingmechanismoftwomethodswasstudiedinbrief.Thewholefoamingprocessinvolvesdecompositionofblowingagent,bubblenucleationandgrowth,bubbleburstandsoon.Thesolid-liquidreactionproductofmagnesiummeltandblowingagentiscarbonmonoxide,whichmademagnesiummoltenexpansion.Mechanismofnucleationisheterogeneousnucleationandbubblesgrowunderthedivingforce,whentheinnerpressureofbubbleistoolarge,thebubblesbegintoburst.Bychangingbubblestabilityfactorssuchasviscosity,surfacetensionandbubblesurfaceadsorption,canreducethebubbleburst.Compressioncurveofmagnesiumfoamwastestedandtheeffectsofporosityandporesizeoncompressivepropertieswerestudied.Theresultshowsthatcompressioncurveofmagnesiumfoamincludinginitiallinearelasticregion,plateauregionanddensificationregion;withtheincreaseofporosityandporesizeinthesamples,locationofcompressioncurve,plateaustressvalueandenergyabsorptioncapacityweredecreased,whilethedensificationstrainvaluewasincreased.KEYWORDS:magnesiumfoam,meltfoamingmethod,powdermetallurgy,foamingmechanism,compressivepropertyCellularmetalsPorousmetalsMetalfoamsMetalsponges0.8[1]Table1-1Characteristicsofthemetalfoamandthedescriptions1-1[1-4](d1mm)1-1[5]Fig.1-1Presentdevelopmentsituationofallkindsofmetalfoams1948Soknik1-2Table1-2Fabricationmethods,propermaterialsandporosityofmetalfoamsAlZnMgAlZnMgAlZnMg85~89%85~89%85~89%AlPbSnMgAlCuMgPbMgSteel65%80~97%60~80%AlBeFeCuAlZnPbSteelBronze60%60~93%20~80%NiCuAgCuSteelNiCuAg90~98%60%90~97%-AlNiCuBeAlFeMgCuTiNi75%5~75%70%(91%)P/%d/mm1g/cm31g/cm3637400.1151231.2.1.1[7]Cymat2005[8]DemetriouMDPd–Cu–Ni–P[9]TakeshiWadaZr-Cu-Al-Ag[9]CymatZr1-2Fig.1-2a)Schematicofpreparingmetalfoambygasinjectionb)Al-foamfabricatedbyCymatCompanyc)Zr-basedamorphousfoam1.2.1.21-3[10]CaSiCMnO2Al2O3Al[11-14][15-19]Fig.1-3Schematicofpreparingmetalfoambymeltfoamingmethodc)b)a)AnyfoamFoamtech[17][19,20][21][22][23][24]1-4Fig.1-4a)Al-foamfabricatedbynovelblowingagentb)SEMimageoftheinnersurfaceofcells1.2.1.3Formgrip[4]TSF[5]Al-9Si/SiCTiH2TiH21-5[19]FormgripTSFFig.1-5Principleoftwo-stepmethodtopreparemetalfoamb)a)1.2.1.41-6[25][26]MgSO4NaCl80%Fig.1-6Principleofvacuuminfiltration1.2.1.5[27]ERGDuocelY.Yamada[28]SG91AAlAZ91Mg1-780%97%Fig.1-7MetalfoampreparedbyInvestmentCastingMethod1.2.1.61987Gardnerb)a)-[29]A.Daoud[30]ZC63-1-8[31]NiFig.1-8ZC63-flyashMg–microballoonfoamcomposites-1-9[32]Fig.1-9Principleofpowder-spacersinteringmethodFig.1-10Foamingofblowingagent-freealuminumpowdercompactsMetalPowdersSpacerParticlesStartingMaterialsMixingPressingHeatTreatments1.Removalofthespacer2.SinteringofMetalFoamMetalFoam15umb)65uma)1bar4bar9barFranciscoGarcia-Moreno[33]1-10L.E.G.Cambronero[34]--[35][36]AndreeIrretier[37]C.E.Wen[38]NiuWenjuan[39]B.P.Neville,A.Rabiei[40]1-11[3]Fig.1-11Metalfoamspreparedbypowdermethodsa)Ti-cellularb)Mg-cellularc)Al-foampreparedwithCaCO3andMarbled)Fe-foame)steelcompositefoamsproducedwith2.0mmstainlesssteelsphereswithstainlesssteelmatrix1.2.3.1IncoInco[41]98%1-12Fig.1-12SEMimagesofAg-foamskeletonpreparedbyElectro-depositionmethod1.2.3.2[42]d)e)CaCO3Marblec)a)b)a)c)b)10~80%1.2.3.3[43]1~10%1.2.4.1AccumulativeRoll-BondingARB[3]KoichiKitazono[44]Al-Mg1-136Fig.1-13Al-MgfoampreparedbyAccumulativeRoll-Bonding1.2.4.2[45]TiNi