Aluminium alloys for demanding applications_2010 Hagen Symposium Reports

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1、2010HagenSymposiumReports:Aluminiumalloysfordemandingapplications12thJan,2011Inthisarticle,thefifthofourreportsfromthe2010HagenSymposium,Germany,DrGeorgSchlieperhighlightsapresentationbyKlausHummertofPLMPowderLightMetalsGmbHinGladbeck,Germany.HummertdiscusseshowPowderMetallurgy(PM

2、)hasfoundroutestoproducespecialaluminiumalloyswithexceptionallyhighstrengthatelevatedtemperatures,highwearresistanceandahighmodulusofelasticity.Aluminiumanditsalloysarewidelyusedmaterials.Aluminiumisreadilyavailableinlargequantities,hasalowspecificweight,excellentelectricalconduct

3、ivity,anattractivesurfaceappearanceandhighcorrosionresistance.Itslimitationsarewhereahighstrengthandstiffness,i.e.ahighmodulusofelasticity,isrequiredandwhereelevatedtemperaturesprevail.Fig.1Tensilestrengthversustemperatureofaluminiumalloys(courtesyPLM)Thelimitsofaluminiumalloyspro

4、ducedbyingotmetallurgy(IM)aregivenbythelowercurveinFig.1.ThemostadvancedAlZnMgCualloysachieveastrengthlevelatroomtemperature(RT)ofupto600MPa.Attemperaturesabove100°CthestrengthbeginstodropdrasticallyandIMalloysarehardlysuitablefortechnicalapplicationsabove200°Cbecausetheylosetoomu

5、chstrength.HighperformancePMaluminiumalloyscanextendtherangeofapplicationtotheuppercurveinFig.1.Twometallurgicalconceptsareemployedforspecialaluminiumalloyswithhighstrengthandwearresistance;precipitationhardeninganddispersionstrengthening.PrecipitationhardeningispossiblebothinIMan

6、dPMalloys,butPMcanapplyhighercoolingratesbecausetheheatcanbeextractedfromasmallpowderparticlemuchfasterthanfromalargervolume.Theresultsaremuchfinerprecipitatesinthepowderoreventhesuppressionofprecipitationinthefirststepandabettercontroloftheamountandstructureofprecipitatesaftercon

7、solidationandheattreatment.Fig.2Processingstepsforhighperformancealuminium(courtesyPLM)Whileprecipitationhardeningimpliesthatthesecondphaseprovidingthehardeningeffectissolubleinthemelt,completelyinsolublephasescanbeintroducedinthematerialbymechanicalalloying(MA).Reactionmilling(RM

8、)isasimilarprocesswhereachemicalr