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MATERIALSSCIENCE&TECHNOLOGY(CTM)

HANDSONACTIVITYWITHHARDNESSTESTER201314Q2StatementofWork(SoW)

Throughthishandsonactivitythestudentswill learnthefundamentalsoftheoperationofahardness testerwhileperforming testson several samples.The studentswillalso recall thetheoreticalknowledgeonmaterialshardnessthattheyacquiredintheframeofCTM.a) Activitiestobeperformedwhileinthelaboratory

1. Selectthemostsuitedhardnesstestforeachmaterialaccordingtothetablesinthe

usersguideofthehardnesstester(seeSection11,Table1,andSection10.1.8.):MATERIAL MOSTSUITEDHARDNESSTESTAl brass ceramic Cu Fe laminatedwood methacrylate Teflon

2. Notedowntheresultsofthehardnesstestsperformedinthelaboratory:SAMPLE HR,TEST1 HR,TEST2 HR,TEST3 HR,TEST4

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b) Activitiestobeperformedashomework

1. ComputetheRockwellhardnessHRfromthefollowingvaluesofdepthtachievedbytheindentatorduringseveraltests.Forthispurpose,usetheformulaintheusersguideofthehardnesstester,consideringthatHRHiscomputedlikeHRF.DisregardthevaluesofHRthatfalloutofatolerancerangeof10%respecttotheaverage:

DEPTHt[mm] HR Variationrespecttoaverage Disregarded?0.098

0.093

0.115

0.095

0.074

0.093

0.095

0.094

0.090

averageHR

notapplicable notapplicable

2. ConvertthepreviousaverageHRvalueintoBrinellhardnessHBS(500kgf,10mmball)andintoVickershardnessHV(15kgf)usingappropriatetablesand/orconversionsfactorslikethosepresentedinreferences[1,2]:

3. ComputetheultimatetensilestressUTSofthestudiedmaterialfromthepreviousHBresultandusingthesameempiricalformulathatappliesformoststeels[1]:

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4. ComputethecorrespondingVickershardnessHVfromthefollowingprintsleftbytheindentatorafterseveralHVtestswithaload15kgf.Forthispurpose,usetheappropriateformulaintheusersguideofthehardnesstesterand/orotherreferencesaboutmaterialsscienceandtechnologylike[1]:

OPTICALMICROSCOPYIMAGES HV

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5. DrawaplotofHRvs.timeintheovenat200C(useHRvaluesobtainedfromtests,inthetableinSectiona)2.).WhichmaybethecauseforthisvariationinHRvs.time?

6. Normalizethecurvesuchthatordinatevaluesrangeonlybetween0and1.Now,assumethatthecurveissigmoidalandfitswelltheAvrami(JMAK)model.ComputethevaluesoftheAvramiindexnandconstantkfortheassociatedAvramiEq.:

7. HowlongshouldweleavethesampleintheovenifwewanttoachieveHR63?

8. Ifweleavethesample285minintheoven,whichwillbethehardnessofthesample?

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9. MakeahypothesisandexplaintherelationshipbetweenthebehaviourofHRvs.time(asshowninSectiona)2.andSectionb)5.)andthemicrostructureobservedinthefollowingTEMimages,consideringthatthematerialisAlCuMgand[3]:

TRANSMISSIONELECTRONMICROSCOPY(TEM)IMAGES OBSERVATIONSAfter200minat200C

After250minat200C

After300minat200C

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References[1]CALLISTER,W.D.,Materialsscienceandengineering:anintroduction.NewYork:JohnWiley&Sons,1985.[2]ASTME14002orASTME140 12be1Standardhardnessconversion tables formetals,AmericanSocietyforTestingandMaterials(ASTM).[3]MACCHI,C.E.,SOMOZA,A.,DUPASQUIER,A.,andPOLMEAR,I.J.,SecondaryprecipitationinAlZnMg(Ag)alloys.ActaMaterialia,51,2003,51515158.Next follow interesting references for thoseof you thatwant tohave a look at scientificinvestigations on mechanical properties of aluminium alloys. These references are notnecessarytocompletetheexercisesproposedinthisSoW:[4]FERRAGUT,R.,SOMOZA,A.andDUPASQUIER,A.,OnthetwostepageingofacommercialAlZnMg alloy; A study by positron lifetime spectroscopy. Journal of PhysicsCondensedMatter,8(45),1996,89458952.[5] LYMAN,C.E. andVANDERSANDE, J.B., TransmissionElectronMicroscopy Investigationofearly stages of precipitation in an AlZnMg alloy. Metallurgical Transactions APhysicalMetallurgyandMaterialsScience,7(8),1976,12111216.[6]REDA,Y.,ABDELKARIM,R.andELMAHALLAWI,I.,ImprovementsinmechanicalandstresscorrosioncrackingpropertiesinAlalloy7075viaretrogressionandreaging.MaterialsScienceand Engineering AStructural Materials Properties Microstructure and Processing, 485(12),2008,468475.[7] SHAW, W.J.D., FRASER, M.A. and NIJJAR, T.S., Effects of reaging 2024T3 and 7075T6aluminium alloys on the microstructure and mechanical properties. Analysis of InServiceFailuresandAdvancesinMicrostructuralCharacterization,26,1999,269276.[8] SHIH, H.C., HO, N.J. and HUANG, J.C., Precipitation behaviors in AlCuMg and 2024aluminum alloys. Metallurgical and Materials Transactions APhysical Metallurgy andMaterialsScience,27(9),1996,24792494.[9]YANNACOPOULOS,S.,KASAP,S.O.,HEDAYAT,A.andVERMA,A.,Anexperimentalstudyofphasetransformations inanAlZnMgZralloy DSCandhotmicrohardnessmeasurements.CanadianMetallurgicalQuarterly,33(1),1994,5160.