The effect of heat treatment on the mechanical and tribological properties of dual size SiC reinforced A357 matrix composites

(1)

w w w . j m r t . c o m . b r

Availableonlineatwww.sciencedirect.com

Original Article

The effect of heat treatment on the mechanical and tribological properties of dual size SiC reinforced A357 matrix composites

Avinash Lakshmikanthan

^a^,^b

, T. Ram Prabhu

^c

, Udayagiri Sai Babu

^d

,

Praveennath G. Koppad

^e

, Manoj Gupta

^f

, Munishamaiah Krishna

^g

, Srikanth Bontha

^a,∗

aDepartmentofMechanicalEngineering,NationalInstituteofTechnology,Surathkal575025,India

bDepartmentofMechanicalEngineering,NitteMeenakshiInstituteofTechnology,Bangalore560064,India

cCEMILAC,DefenceR&DOrganization,Bangalore560093,India

dDepartmentofMaterialsEngineering,IndianInstituteofScience,Bengaluru560012,India

eDepartmentofMechanicalEngineering,DayanandaSagarCollegeofEngineering,Bengaluru560078,India

fDepartmentofMechanicalEngineering,TheNationalUniversityofSingapore,10KentRidgeCrescent,119260Singapore,Singapore

gDepartmentofMechanicalEngineering,RVCollegeofEngineering,Bengaluru560059,India

a r t i c l e i n f o

Articlehistory:

Received21February2020 Accepted7April2020 Availableonline4May2020

Keywords:

Dualparticlesize(DPS)composites Stircasting

T6heattreatment Microstructure Mechanicalproperties Aging

Wear

a bs t r a c t

Inthepresentwork,theeffectofagingtemperatureandparticlesizeratioofSiCparticleson themechanicalandtribologicalpropertiesofA357compositesreinforcedwithdualparticle sizeSiCwereinvestigated.Thecompositeswerepreparedbymelt-stirringassistedperma- nentmoldcastingtechniquewithdifferentweightfractions(3%coarse+3%fine,4%coarse +2%fine,and2%coarse+4%fine)oflargeandsmallsizeSiCparticles.Thesethreeprepared compositesarereferredasDPS1,DPS2andDPS3composites.Thesolutionizingtempera- turewasmaintainedconstantat540^◦Cfor9hwhiletheagingwasdoneat160^◦C,180^◦C and200^◦C(T6treatment)for6h.Opticalandscanningelectronmicroscopystudiesshowed fairlyuniformdispersionofdualsizeSiCparticlesinA357matrixwithgoodinterfacial bonding.High-resolutiontransmissionelectronmicroscopyimagesshowedformationof uniformlydispersedneedle-like␤phaseandsphericalshaped␤-Mg2Siprecipitatesunder peakagingconditions.ComparedtoT6treatedA357alloy,theT6treatedDPSA357com- positesshowedimprovedyieldstrength,tensilestrength,hardnessandwearresistance.

Amongthethreecomposites,hardnessandwearresistanceofT6treatedDPS2composite wasfoundtobesigniﬁcantlyhigherwhencomparedtotheothertwocomposites(DPS1and DPS3).Ratiooflargeparticlestosmallparticlesalsoseemstoeffectthemechanicaland tribologicalproperties.Presenceofmoresmallparticleswasfoundtobegoodforstrength andductilitywhereasmorelargeparticleswerefoundtobegoodforhardnessandwear resistance.

∗ Correspondingauthor.

E-mail:[email protected](S.Bontha).

https://doi.org/10.1016/j.jmrt.2020.04.027

creativecommons.org/licenses/by-nc-nd/4.0/).

(2)

1. Introduction

Owingtotheirlowdensity,highspecificstrength,andhigh wearresistance,aluminum-basedmetalmatrixcomposites arethemostpromisingmaterialsforvariousautomotiveand aerospace applications [1–4]. In particular, Al-Si-Mg alloys suchas A356 and A357 are used in many critical applications like pistons, engineblocks, brake calipers, impellers, pump,andvalvecomponents.Theprimaryreasonsforusing these alloys for above applications are their high specific strength, excellent weldability, castability, and good corro- sionresistance.However,themechanicalpropertiesarehighly influencedbymicrostructure,chemicalcomposition, solidi- ficationconditions,and heattreatment.ThepresenceofSi andMgalongwithappropriateheattreatmentresultsinthe formationofMg2Siprecipitates,whichimprovethestrength significantly.Thegeneralprecipitationsequencecanbegiven as,GP-IZones→GP-IIzones/␤ (Mg5Si6,FCCstructure)→␤ Intermediateprecipitate→␤(Mg2Si,hexagonalstructure)precipitates.Theage hardeningresponseofA357alloylargely dependsonfactorslikechemicalcomposition,solutionizing, andagingtemperatures,whichinturndeterminethemechan- icalproperties[5–9].

Al-Sialloy-basedmetalmatrixcompositesarefabricated usingbothliquidandpowdermetallurgyroutes.Theselec- tionofappropriateprocessingtechniqueisbasedonthetype andweightfractionofreinforcement,itsmorphologyandthe endapplicationoftheprocessedcomposite[10–15].Canakci etal.[10,11]usedpowderprocessingtechniqueforfabrication ofAlbasedMMC’s.Heretheyusedmethanolasaprocesscon- trolagent.Theyevaluatedthemicrostructureandmechanical propertiesofthedevelopedAl-MMC’s.Canakcietal.useda novel methodfor the fabricationof AA7075 powders from recycledchips usingmechanicalmilling[12].Canakcietal.

alsousedstircastingtechniquetofabricateAA2024composite reinforcedwithB4Cparticlesandstudiedtheeffectofparti- clesize,volumefraction,andwearbehaviorofthedeveloped MMC’s.Furtherartiﬁcialneuralnetwork(ANN)techniquewas usedtopredictthemechanicalbehaviorofdevelopedMMC’s [13–15].

Zulﬁaetal.[16]intheirworkusedacombinationofstir castingandhotisostaticpressingtechniquesforfabrication ofA357/SiCcomposites.Thecompositeswith15%SiCwere initiallyfabricatedusingstircastingfollowedbyhotisostatic pressing at550^◦C. Badiziet al. [17] usedstir casting tech- niquetofabricateA357compositewith1.5%SiC.Theyused aresistancefurnaceequippedwithanelectromagneticstir- rertoprocess thecomposite. Inanother work,Datta etal.

[18]studiedthecorrosionbehaviorofpowdermetallurgypro- cessedAl-Si-Mg/SiCcomposite.ElementalpowdersofAl,Si andMgalong with2%SiCwere mechanicallyalloyed, cold pressedandthensinteredtoobtaincomposite.Overall,stir castingtechniqueisusedtoproduceAl-Sicompositesowing toitﬂexibilityandlowcostofprocessing.

Takingacuefromitsgoodmanufacturingandmechani- calcharacteristics,severaleffortshavebeenmadetoreinforce Al-Si-Mgalloywithceramicparticulates.Themostcommonly usedceramicparticlesinclude,SiC,TiC,TiB₂,andAl₂O₃,out ofwhichSiCisanoutstandingchoiceduetoitslowdensity,

highhardness,highelasticmodulusandexcellentchemical inertness.Yuetal.[19]studiedthereinforcingmechanismof TiB2inas-castA357/TiB2insitucomposites.Itwasobserved that mechanicalpropertiesincreasedduetoanincreasein dislocationdensityneartheboundaryof␣-AlandTiB₂particles. Kandemir et al.[20]studied themicrostructure, and mechanicalpropertiesofSiCreinforcedA357compositespro- cessed by ultrasoniccavitation method. Thehardness and tensilestrength ofthecompositeincreasedfrom60HVand 138MPato73HVand198MParespectivelywhenA357alloy wasreinforcedwithSiCparticles.Thestrengtheninginthe compositewasattributedtograinsizereductionandOrowan mechanism.However,theeffectofload-bearingmechanism wasfoundtobeminimal.Leonardetal.[21]comparedtheslid- ingwearbehaviorofA357alloysand30vol%SiCreinforced A357compositesatdifferentloadsrangingfrom6–74N.They observedthatatalowerloadof6N,theaveragewearcoef- ficientofthecompositewasfoundtobesignificantlylower than thatofthealloy.Atahigherloadof74N,theaverage wearcoefficientanddepthofdeformationofthecomposite wastwicethatofthealloy.

On theother hand,several works reportedthe effectof heat treatment on mechanical properties of A357 and its composites. Bloyceand Summers [22]studiedthe effectof heat treatmentonmechanicalproperties ofA357/SiC composites.Outofthetwoheattreatmentproceduresopted,the onewith540^◦Csolutionizingand160^◦Cagingtemperature showedbettermechanicalpropertiesforbothA357alloyand composites.Taghiabadietal.[23]reportedtheeffectofheat treatmentonascastAl-Si-MgcompositesreinforcedwithTiB2

particles.Tensilestrengthoftheheat-treatedcompositeswas foundtobehigherduetothestrengtheningeffectprovidedby Mg₂Siprecipitates.StrengtheninginagehardenedA356/TiB₂ compositeswasattributedtotheformationof␤,␤(Mg2Si)precipitates.Dislocationpining,andtheirpileupsinthevicinity ofTiB2particleswerealsoreported[24].Itiswellknownthat themechanicalpropertieslikestrengthandwearresistance ofcompositeslargelydependonthesize,amount,morphol- ogyanddispersionofreinforcementinthemetalmatrix.In particular,theeffectofsizeofparticlesplaysavitalrolein decidingthestrengthandductilityoftheresultingcompos- ites. Micron-sized particles improvestrength atthe costof signiﬁcant lossinductilitywhilesub-micronor nano-sized particlesimprovenotonlythestrengthbutalsotheductility.

Thishasledtoseveralstudiesonthedevelopmentofbimodal ortrimodalparticlereinforcedcomposites[24–27].Bindumad- havanet al.[25]studiedtheeffect ofdualsizeSiC(47 and 120␮m)onimpactenergyandwearrateofAl-Si-Mgcompos- ites.TheimpactenergyofdualsizeSiCcomposite(12.2J)was muchhigherthanthatofsingleparticlesizecomposite(6.7J).

Further,theweightlossduringweartestwaslessincaseof dualsizeSiCcomposite(30mg)whilehigherincaseofsin- gleparticlesizecomposite(47mg).Sharmaetal.[28]studied theeffectofbimodalsillimanite(1–20␮mand75–106␮m)on dry slidingwearbehaviorofAl-Sicompositesfabricatedby stircastingtechnique.Al-Sicompositehavingahigherweight fractionofsmall-sizedparticlesandlowerweightfractionof largeparticles (3:1)showed thehighestnano-hardnessand lowestwearratewhencomparedtoothercombinations.Over- allbimodalsizedreinforcement-basedcompositesarequite

(3)

attractiveoverconventionalcompositeswithsinglesizerein- forcement.Sofar,limitedworkhasbeenreportedontheeffect ofheattreatmentonmechanicalandtribologicalproperties ofA357compositereinforcedwithbimodalSiCparticles.The other aspectwhichisnot yetstudiedsystematicallyisthe effectofratiooflargetosmallparticlesonthemechanicaland tribologicalproperties.Findingtheoptimumratiooflargeto smallparticlesizeandvariationofpropertieswiththisratiois expectedtoprovidemoreinsightsintotheroleofbimodalpar- ticlereinforcementsinimprovingpropertiesofcomposites.

Inthepresentwork,anattemptismadetounderstandthe effectofheattreatmentonthemechanicaland tribological propertiesofA357compositesreinforcedwithdualsizeSiC particles.Theeffectofsolutionizingandvariousagingtem- peraturesalongwithdifferentweightfractionsofdualsize SiCparticlesonmicrostructure,strength,andwearresistance isstudied.Thestudywillfurthertheunderstandingofeffect ofagingtemperatureandratiooflargetosmallparticlesize onpropertiesofA357compositesreinforcedwithdualsizeSiC particles.

2. Experimental procedures

2.1. MaterialsandDPS-SiCcompositefabrication method

Al-7.4Si-0.54Mg (A357 alloy) with a theoretical density of 2.7g/ccwasselectedasamatrixmaterial,andSiCoftwodif- ferentparticlesizes(140±10␮m(Large)and30±5␮m(Small)) havingadensity3.21g/cc[29]wereusedasreinforcements.

TheSiCpowdersamples(twodifferentmeshsizes)andtheir morphologywithEDSanalysisareshowninFig.1(a)–(d).The fabrication ofA357dual particle size compositeshas been describedindetailinourpreviouswork[30,31].Imagesofcast sampleareshowninFig.2.Theprocessﬂowchartforfabrica- tionofA357compositereinforcedwithdualsizeSiCparticles ispresentedinFig.3.

As-cast A357 alloy and its DPS composites were sub- jectedtoT6heattreatmentorprecipitationtreatmentusing a mufﬂe furnace equipped with a temperature controller.

The T6-heat treatment process consists of solutionizing, quenching, and aging. Theas-cast A357 alloy and its DPS composites were T6 heat treated using temperature-time cycles as shown in Fig. 4 and the description is provided below.

Step1:Solutionizingatatemperatureof540^◦C±2^◦Cfor9h whichiswidelyusedforproductionofA357alloysandits composites[32–34].

Step 2: Quenching in water to room temperature with a quenchdelaytimerestrictedto5–6s.

Step3:Aginginatemperaturerangeof160^◦Cto200^◦Cin stepsof20^◦Cfor6h.

Theprecipitationheat-treatment(T6)cyclesshowninFig.4 fordifferentcasesaredesignatedasfollows:

(a) 540^◦C(SolutionTreatment)for9h–quenchinginwater

−160^◦C(aging)for6hisdenotedby540-9H-160-6H.

(b) 540^◦C(SolutionTreatment)for9h–quenchinginwater

Fig.1–MorphologyofSiCparticles,(a)SiCpowdersample(ﬁnesize)(b)MorphologyofﬁnesizeSiCparticleswithEDS analysis(c)SiCpowdersample(coarsesize)and(d)MorphologyofcoarsesizeSiCparticleswithEDSanalysis.

(4)

Fig.2–Imagesofcastsamples.

Fig.3–ProcessﬂowchartforfabricationofA357compositereinforcedwithdualsizeSiCparticles.

Fig.4–Precipitationheattreatment(T6)cycles.

(5)

Table1–Thealloy/composite,heattreatment,weightfractionofSiCparticlesandtheirdesignation.Herein,L:S correspondstoratioofwt.%ofcoarse(140±10␮m-L)andﬁne(30±5␮m-S)particlesofDualParticleSizeSiC.

Alloy/Composite HeatTreatment L:S(wt.%) Designation

(T6-treated)

As-CastA357alloy 540-9H-160-6H

Nil

A357-160^◦C–6H

As-CastA357alloy 540-9H-180-6H A357-180^◦C–6H

As-CastA357alloy 540-9H-200-6H A357-200^◦C–6H

DPS1Composite 540-9H-160-6H

3:3

DPS1-160^◦C–6H

DPS1Composite 540-9H-180-6H DPS1-180^◦C–6H

4:2

DPS2-160^◦C–6H

2:4

DPS3-160^◦C–6H

(c) 540^◦C(SolutionTreatment)for9h–quenchinginwater

Thealloy/composite,heattreatment,weightfractionofSiC particlesandtheirdesignationispresentedinTable1.

2.2. PhaseanalysisandMicrostructural characterization

Theheat-treatedsamples(A357alloyanditsDPScomposites) werefurthercharacterizedaspersuitableASTMstandards.

Thecharacterizationandtestingcarriedoutonthesesamples issummarizedinFig.5.

XRD analysis of samples was conducted using X’Pert³ Powderdiffractometer(PANalytical,Malvern,UK)withCuK␣ radiation.Thestudywasperformedforthescananglerange of20^◦ to80^◦ atascanspeedof2^◦/min.BeforeXRDstudies, thesampleswerecleanedwithacetoneandwerealsodriedin air.UsingstandardmetallurgicalproceduresasperASTME3- 17standardsthecompositeswerepolishedandetchedwith Keller’sreagent.Optical(Model:NikonLV150)andscanning

electronmicroscopy(Model:TESCANVega3LMU)studieswere carriedouttocheckthedispersionandbondingofSiCparticles withA357matrix.Inordertostudytheprecipitatesanddis- locations,transmissionelectronmicroscopyexaminationwas conductedusingJEOLJEM2100HighResolutionTransmission ElectronMicroscope(HRTEM).Forthis,samplesof3mmdiam- eterand10␮mthickwere preparedusingionbeammilling (Model691,Gatan).

2.3. Densitymeasurements

Theexperimentaldensity(exp)oftheA357alloyanditsDPS composites was measured using the Archimedes principle (ASTMD792-66standard)and,thetheoreticaldensity(th)was calculatedusingtheruleofmixtures[13,14,35,36].

2.4. Mechanicalandweartesting

ThehardnesstestwascarriedoutusingaMicroCumMacro- Vickers hardness testing machine (Model: VH1150) as per ASTM E384 standard. Tensile test was conducted as per

Fig.5–FlowchartofcharacterizationandtestingcarriedoutonDPS-SiCreinforcedA357MMCs.

(6)

Table2–Theoreticaldensity(th)andexperimentaldensity(exp)ofA357alloyanditsDPScomposites(T6-heattreated).

S/No Alloy/Composite Designation Theoreticaldensity(gm/cc) Experimentaldensity(gm/cc)

1 As-CastA357alloy A357-160^◦C–6H 2.700 2.685

2 DPS1Composite DPS1-160^◦C–6H 2.730 2.713

ASTME8M-15astandardtoevaluatetheyieldstrength,tensile strengthandductilityoftheheat-treatedcomposites.Tribo- logicalpropertiesi.e.wearratewasobtainedbyconducting dryslidingweartestusingpin-on-discmachine(ModelTR- 20LE,Ducom,India)asperASTM-G99standard.Forweartests, appliedloadwasvariedfrom10Nto30Ninstepsof5Nat aﬁxedsliding velocity of2.5m/sec and sliding distanceof 1500m.Fracturesurfacesaftertensiletest,wornsurfaceand weardebrisafterweartestwerestudiedusingscanningelec- tronmicroscope.

3. Results and discussion

3.1. DensitymeasurementresultsofA357alloyand itsDPScompositeatT6-heattreatedcondition

Table 2 shows the density measurements (theoretical and experimental)ofA357alloyanditsDPScompositesatvarying agingtemperatures(160^◦C,180^◦C,and 200^◦C).Thedensity valuesoftheDPScompositesareslightlyhighercomparedto theA357alloy.Thisisduetothepresenceofahigh-density ceramic material (SiCp) [13,37]. Variations in the density amongthecompositesheattreatedtodifferentconditionsare negligible.FromTable2,wecanobservethatthedifference inthetheoreticalandexperimentaldensitiesisinsigniﬁcant.

Thus,itcanbeconcludedthatthedispersionofSiCparticles wasfoundtobegoodwithalmostnoobservableporosityor anycastingdefects[38,39].

3.2. PhaseanalysisofA357alloyatT6-heattreated condition

Fig.6showstheXRDpatternsofA357alloyatdifferentaging temperatures(160^◦C,180^◦C,and200^◦C).TheXRDanalysisof A357alloyrevealsthepresenceofAlandSiasmajorpeaks.

Inaddition,smallpeaksofMgandMg2Siintermetallicphases weredetectedwhichshowsthatMgand SiformtheMg2Si intermetallic precipitates as shown by EDS analysis. From theﬁgure,itcanbeobservedthatastheagingtemperature increases,theintensityofthepeaksalsoincreases.Similar trendshavebeenreportedinliterature[40].

Fig.6–(a)XRDpatternsofA357alloyatdifferentaging temperatures(a)XRDpatternofA357alloyat

540^◦C-9H-160^◦C-6H(b)XRDpatternofA357alloyat 540^◦C-9H-180^◦C-6H(c)XRDpatternofA357alloyat 540^◦C-9H-200^◦C-6H.

3.3. MicrostructuralanalysisofA357alloyatdifferent conditions(un-treatedandT6-heattreated)

Fig.7(a)showstheopticalmicrographofas-castA357alloy (untreatedcondition).Themicrographconsistsoftwophases namely␣-AlphaseandAl-Sieutecticphase.Themicrostruc- ture islargely dominated bycoarsesize ␣-Al grains which aresurroundedbyeutecticSiregionsrepeatedinperiodiccell patternsthatareﬁbrousinshape.

Fig. 7(b) and (c) show the optical micrographs of A357 alloysolutiontreatedat540^◦Candagedat180^◦Cand200^◦C respectively. InFig. 7(b)ﬁneglobular morphologyofeutec- ticsiliconparticles duetoheattreatmentcanbeobserved.

Similarresultswerereportedbyresearchers[41,42].Heattreat- mentresultsinthetransformationofﬁbrousshapeeutecticSi intoﬁnespheroidizedSiparticlesuniformlydistributedinthe A357matrix.Heattreatment alsodissolves Mg2Siparticles, results instructural homogenization, and alters the shape ofeutecticSiparticles.Uponheattreatmentneckingcanbe seen in Si particles. With further increase in temperature from 160–180^◦C,particle fragmentationand spherodization

(7)

Fig.7–(a)Opticalmicrographofas-castA357alloy(untreatedcondition)(b)Opticalmicrographofas-cast357alloyat 540^◦C-9H-180^◦C-6H(c)Opticalmicrographofas-cast357alloyat540^◦C-9H-200^◦C-6H(d)SEMmicrographwithEDS spectrumat540^◦C-9H-180^◦C-6H.

takesplace(Fig.7(b))[32,33].Further,fromFig.7(b)itcanbe observedthattheSiparticlesaresmallerandmoreuniformly distributed.ThefragmentationofSiparticlesreducesthepar- ticlesizeandincreasesparticlenumber,whichinturnleads tothestrengtheningofthealloy.Astheagingtemperatureis increasedfrom180^◦Cto200^◦C,coarseningofSiparticlescan beobserved(Fig.7(c)).

Fig.7(d)showstheSEMmicrographwithEDSspectrumof A357alloysolutiontreatedat540^◦Candagedat180^◦C.From theEDSspectrum,tracesofMglocatedattheAl-Siinterfaces canbefound.Typically,MgisaddedtotheAl–Sialloyforage hardeningthroughtheprecipitationofMg2Siprecipitates.In Fig.7(d),magnesiumpeakfromtheEDSanalysisconﬁrmsthat Mg₂Siprecipitatesformasaresultofheattreatment.

3.4. MicrostructuralanalysisofDPScompositeat T6-heattreatedcondition

Fig. 8(a)–(c) shows the optical micrographs of heat-treated composites (solution treated at 540^◦C and aged at180^◦C) DPS1,DPS2andDPS3respectively.Itcanbeobservedfromall themicrographsthatbothdualsizesSiCparticleswerefound tobefairlyuniformlydistributedintheA357matrix.Fig.8(a) showsmicrographofDPS1compositewherethedispersionof

SiCparticleswasfoundtobeverygoodwithalmostnoobserv- ableporosityoranycastingdefects.However,asmallextentof clusteringofsmallsizeSiCparticleswasobservedinthecase ofDPS2compositeasshowninFig.8(b).MostoftheSiCparti- clesseeninmicrostructureareoflargesize,whichisduetothe highcontentoflargesizeparticleswhencomparedtosmall sizeparticles.Ontheotherhand,thedispersionofparticlesin DPS3compositewasreasonablyuniform,asshowninFig.8(c).

Small-scaleclusterformationofsmallsizeSiCparticleswere seenatfewspotsclosertolargeSiCparticlesinDPS3com- posite.Highshearrategeneratedduringmelt-stirringprocess pushessmallsizeparticles atafasterratewhencompared tolargeparticles.However,themovementofsmallparticles isrestrictedbylargeparticlesduetowhichtheygetsettled nearthem,andsameisseeninFig.8(b).Overalldispersionof dualsizeSiCparticleswasfoundtobereasonablyuniformin allthecompositesystems,andhardlyanycastingdefectlike porositywasseenonthesurface.TheadditionofSiCasrein- forcementenhancesagingkinetics,phaseformationreaction anditalsoactsasseedingforprecipitationduringtheheat treatmentprocess,whichfurtherleadstoalloystrengthening [43–45].ThesedualsizesSiCparticlesinﬂuencethestrength- eningofmatrixmaterialinasigniﬁcantwayduringtheheat treatmentprocess[45–48].

(8)

Fig.8–MicrographsofDPScompositesagedat540^◦C-6H-180^◦Cconditions.(a)OpticalmicrographofDPS1compositeat 180^◦C(b)OpticalmicrographofDPS2compositeat180^◦C(c)OpticalmicrographofDPS3compositeat180^◦C.In(a)–(c),1 representsﬁneSiCp,2representscoarseSiCp,3showsclusteringofﬁneSiCp(d)EDSspectrumtakenonDPS2composite particleand(e)EDSspectrumatAl/SiCinterface.

Fig.8(d)showstheEDSanalysisofcompositeparticle in DPS2 composite. From the ﬁgure, Si and C peaks can be observedfrom the elementaldiffractionscanning analysis.

Si,CpeaksconﬁrmthepresenceofSiCparticlesintheA357 matrix.Fig. 8(e)showsEDSanalysisattheAl/SiCinterface.

TheinterfaceshowsthepresenceofMgpeakalongwithAl,Si andCpeaks.ThepresenceoffourelementsAl,Mg,Si,andC conﬁrmsthepresenceofMg2SiattheAl-SiCinterface.

3.5. TEManalysisofA357alloyanditsDPScomposite atT6-heattreatedcondition

Precipitation is a very important aspect of age hardening whichdirectlyinﬂuencesthemechanicalpropertiesofamate- rial.Fig.9showsthebright-ﬁeldTEMimagesofbothA357alloy anditscompositeswithdualsizeSiCparticlesthatwereaged at180^◦Cforabout6h.TEMimageofA357alloyasdepicted

(9)

Fig.9–Bright-ﬁeldTEMimagesofbothA357alloyanditsDPScompositesagedat540^◦C-6H-180^◦C.(a)A357alloy(b)DPS1 composite(c)DPS2composite(d)DPS3composite(e)modiﬁedSiparticleswithtwinsinDPS2composite.FromtheMarking 1representneedleshaped␤phase.

inFig.9(a)showsthepresenceofveryﬁnesizedprecipitates consisting ofMgand Si atoms.These ﬁne shapedprecipi- tateswhichweresphericalinshapecorrespondto␤–Mg2Si withdiameterintherangeof20–40nm.Apartfromthesepre- cipitates, fewneedlescorresponding to␤ phasewere also observedintheA357alloy.IncaseofDPS1andDPS2,along

withthe␤–Mg2Siprecipitates,needlesof␤phasewasalso observedasshowninFig.9(b)and(c).ComparedtoA357alloy, needle shaped␤ phasewascomparatively high incaseof thesecomposites.Mostoftheseﬁneneedleshadlengthinthe rangeof30–100nmanddiameterofabout∼5nminthepeak- agedheat-treatedconditions.Duetohighsiliconcontentin

(10)

thematrix,quenchinggivesrisetohighercontentofsupersat- uratedSiwhichfavorstheformationof␤phase[49].Further ahighmagniﬁcationTEMmicrographasshowninFig.9(d)of DPS3compositeshoweduniformdispersionof␤–Mg2Sipre- cipitatesintheentire␣-Almatrix.Further,presenceofhigh siliconcontent inA357matrix requiredabovethestoichio- metricformationof␤–Mg2Siwillnotonlyfavorthenucleation oftheseprecipitatesbutalsostrengthofbothA357alloyand DPScomposites.However,itisinterestingtonotethatinboth A357alloyandcomposites,no␤phasewasobservedwhich otherwise isconsidered tobe nucleationsite for ␤ phase [50,51].Fig.9(e)showsasmallcrystalofsiliconparticlewhose edgesaremoreroundedindicatingspheroidization.Darkcon- traststructuresresemblingtwinboundariesanddislocation networksarealsoseeninsidethesiliconparticle.Themor- phologicalchangesfromirregulartonearlyroundshapeand decreaseinsizefromcoarsetosmallaremainlyduetosolu- tiontreatment.Inadditiontothis,formationof␤precipitates generatestressesinthematrixwhichiscompensatedbythe modiﬁcationinsiliconparticle[52].

3.6. Inﬂuenceofagingtemperatureontensile propertiesofA357alloyanditsDPScomposites

Fig.10(a)and(b)showthevariationoftensilestrength(ultimate&yield)ofA357alloyanditsDPScompositesatvarying agingtemperatures(160^◦C,180^◦C,and200^◦C).FromFig.10(a) and(b)itcanbeobservedthattheadditionofparticulaterein- forcement enhancesthe tensilestrength ofthecomposites [53,54].Althoughallcompositessubjectedtoheattreatment givenearlysame tensilestrength (ultimate&yield) values, theDPS3compositeexhibitedslightlybetterstrengthproper- tiesinallthreeagingconditionsfollowedbyDPS1andDPS2.

Strengtheningeffectincompositescanbeattributedtonum- ber of particles present in a composite. Even though, the weightfractionofSiCissameforallcomposites,numberof particlesishighestinDPS3becauseoflargefractionofsmall particles.AfterDPS3,DPS1andDPS2havemorenumberof smallerparticlesinthatorder.SiCparticlesactasdislocation pinningsitesandhencecanimprovestrength.Possiblegrain reﬁnement due toSiC particles and effectiveload transfer

Fig.10–TensiletestresultsofA357alloyanditsDPScompositesatvaryingagingtemperatures.Arrowsindicatedirection ofincreasingstrengthandnumbersonlinesindicateratiooflargetosmallparticles.

(11)

Fig.11–DuctilityresultsofA357alloyanditsDPScompositesatvaryingagingtemperatures.Arrowindicatesdirectionof increasingductilityandnumbersonlinesindicateratiooflargetosmallparticles.

frommatrixtocompositeparticlesarealsoexpectedtoplaya roleinincreaseinthestrengthvaluesofcomposites.So,the strengtheningofcompositesisaresultofsynergisticeffect ofgrainreﬁnement,precipitationhardening,Orowanlooping andefﬁcientloadtransfer[55–60].

Further,fromFig.10(a)and(b),itcanbeobservedthatthe strengthvaluesincreasewithincreaseinagingtemperature from160^◦Cto180^◦Cbuttendtodropasthetemperatureis increasedto200^◦C.Itshouldbenotedthathigheststrength valuesareobservedat180^◦Cagingtemperature.Uponaging, increase in strength properties are due to precipitation of coherent␤–Mg₂Siparticles.Uponoveraging,lossincoherence leadstolossinstrength.

Fig.11showsthevariationofpercentageelongationofA357 alloyanditsDPScompositesatvaryingagingtemperatures.

FromFig.11,itcanbeseenthatthecompositesexhibitlower ductility(measuredas%elongation)whencomparedtothe alloyatallagingtemperatures.PresenceofSiCparticlescould leadtoreductioninductilitybecausetheycanactasnucle- ationsitesforcracksandthushastenfailure.Themechanism offractureappearstobechangingfromalloytocomposites.

Also,fromFig.11,itcanbeobservedthatastheagingtem- peratureincreasesductilityincreasessubstantiallyforA357 alloywhereasitincreasesmarginallyforcomposites.Increase inductility inA357 alloy withaging temperature could be duetochangeinfracturemechanismfrominterdendriticto intradendriticuponoveraging(Fig.12(a)and(b)).Whereasfor composites,agingtemperaturehaslittleeffectbecausefrac- turemechanismremainstobeparticlepulloutirrespectiveof agingtemperature(Fig.12(c)–(h)).Analogoustrendshavebeen reportedinliterature[52].

3.7. FractographsofA357alloyanditsDPS compositesatvaryingagingtemperatures

TensilefracturesurfacesofA357alloyanditsDPScompos- iteswereanalyzedusingSEMandareshowninFig.12(a)–(h).

For the cases of 180^◦C and 200^◦C, large numbers of den- drite fractured regions were observed in the fractograph (Fig.12(a)and(b)).Thisconfirmsinter-dendriticcrackingasthe mainfracturemechanismasthesedendriteglobulespromote micro-crackpropagationduringtheloading[61].Ontheother hand,allDPScomposites(DPS1,DPS2andDPS3)atbothaging temperatures i.e. 180^◦C for6h. and 200^◦C for6h, showed nearlyidenticalfracturesurfaces.Thefracturesurfacescon- sistedofalargenumberofdimplesindicatingductilefailureby voidnucleationandcoalescencemechanisms.Thevoidnucle- ation takesplaceatAlmatrix/SiCinterface.Whenstressis applied,theplasticdeformationstartsbydislocationmove- ment. These dislocationsare blocked by the Almatrix/SiC interfacesresultingindislocationaccumulation.Thisbuilds upthestressaroundtheinterfacesresultinginmuchhigher stressthantheappliedstress.Whenthestressissufficientto cracktheinterface,themicrovoidpreferablynucleatesatthe interfaceduetostrongstressgradient.Duetothecreationof micro-voids,thecrackinitiatesatthemicrovoidandprop- agatesaroundtheSiCparticles.Eventually,theparticlesare pulledoutoftheA357matrixleavingbehindnearlycircular shapedvoids.Thesevoidsconnectwitheachotherthrough crackpropagationandfinallyleadtofractureformingadim- pledfracturedsurfaceasseeninFig.12(c)–(h).

3.8. Inﬂuenceofagingtemperatureonhardnessof A357alloyanditsDPScomposites

Fig. 13 shows the variation of hardnessof A357 alloy and its DPS composites at varying aging temperatures (160^◦C, 180^◦C,and200^◦C).TheDPScompositesshowedanincrease inhardnesswhencomparedtoA357alloyatvaryingaging temperatures.Higherhardnessvaluesofcompositescanbe attributedtothepresenceofhardSiCparticles.Amongthe composites, DPS2 composite shows highest hardness and DPS3showsthe lowesthardnessatallthreeagingtemper- atures. This trend in hardness among composites can be

(12)

Fig.12–FractographsofA357alloyanditsDPSCompositesatvaryingagingtemperatures.Where(a)&(b)A357alloyat agingtemperatureof180^◦Cand200^◦C,(c)&(d)DPS1compositeatagingtemperatureof180^◦Cand200^◦C,(e)&(f)DPS2 compositeatagingtemperatureof180^◦Cand200^◦C,(g)&(h)DPS3compositeatagingtemperatureof180^◦Cand200^◦C.

rationalizedbasedonweightfractionoflargeSiC particles.

Smallsizeparticlesofferlessresistancetodeformationwhen comparedtocoarsesizeparticlesandhenceleadstolowhard- nessvalues[30,31]. HighesthardnessofDPS2composite is duetothepresenceofhighestweightfractionoflargesized particles.Similarly,lowesthardnessvaluesexhibitedbyDPS3 compositeisduetothepresenceoflowestweightfractionof largesizedparticles.

FromFig.13itcanbeobservedthatthehardnessvalues increase withaging temperature till 180^◦C where it peaks and reducesbeyond180^◦C.The increaseinhardness after heattreatmentcanbeattributedtoformationofhardMg2Si phasedueprecipitationhardening[62].Accordingtothepeak

hardnessvariationwithdifferentagingtemperatures,itwas foundthatthecompositeisunderagedat160^◦Candover- agedat200^◦C.Analogoustrendswerereportedinliterature [44,45,63].

3.9. SpeciﬁcwearrateofA357alloyanditsDPS compositesatvaryingagingtemperatures

Fig.14showstheplotofspeciﬁcwearrate(at30N)v/saging temperatureofA357alloyanditsDPScomposites.FromFig.14 it can be observed that as-cast alloy (A357) displayed the highestwearrate.ThereasonforhighestwearrateinA357 alloy can bedue toreasons suchas extensive subsurface

(13)

Fig.13–HardnesstestresultsofA357alloyanditsDPScompositesatvaryingagingtemperatures.Arrowindicates directionofincreasinghardnessandnumbersonlinesindicateratiooflargetosmallparticles.

deformation,highadhesivemetal-metalcontactassistedsur- face shear strain, the increasedcontact area of matrix to counter surface, and the absence ofload bearing particles [30,31,64].FromFig.14,itcanalsobeobservedthatDPScom- positesshowlesswearratewhencomparedtoA357alloy.This canbeattributedtothepresenceofhardSiCparticlesinDPS composites.SiCparticlesarehardandhencetheycanresist abrasion.Moreover,theyalsoreducecontactbetweencounter surfaceandsoftmatrixandsharesomeload.Reducedcontact betweencountersurfaceandmatrixandloadsharingleadsto reducedwearrate[65,66].Amongthecomposites,theDPS2 compositedisplayedleastwearratewhencomparedtoDPS1 andDPS3compositesatall agingtemperatures.Good wear resistance(leastwearrate)ofDPS2ismainlyduetopresence ofhighweightpercentoflargesizedSiCparticleswhichbear mostoftheappliedpressurethanthatofsmallsizedSiCpar- ticlesandA357matrix.Further,largesizedSiCparticleprotect thesmallsizedSiCparticlesfromgougingoutofthematrix therebyallowingthemtoprovideprotectionagainstweight lossforalonger time[25,31,67–69]. Itisinterestingtonote

therelationbetweenagingtemperaturesandwearresistance.

FromFig.14,itcanbeobservedthatbothA357alloyanditsDPS compositesshowdecreaseinwearratewithagingtempera- turetill180^◦Cbutbeyondthistemperaturewearrateappears tobeincreasing.Thespecimensagedat180^◦Cshowedbet- terwearresistancecomparedtothespecimensagedat160^◦C and200^◦Canditmaybeduetothepresence␤and␤-Mg₂Si precipitates[70,71].Thus,thespecimensagedat180^◦Ccanbe consideredaspeakagedandthespecimenswhichareagedat 160^◦Careconsideredasunderagedandthespecimenswhich areagedat200^◦Careconsideredasoveraged.Similarresults werereportedbyseveralresearchers[63,72].

3.10. WornsurfaceanalysisofA357alloyanditsDPS compositesatvaryingagingtemperature

WornsurfacesofbothA357alloyanditsDPScompositesaged atdifferenttemperaturesof180^◦Cand200^◦Ctakenat30N loadareshowninFig.15(a)–(h).

Fig.14–EffectofagingtemperaturesonwearrateofA357alloyanditsDPScomposites.Arrowindicatesthedirectionof lowerspeciﬁcwearrateandnumbersonlinesindicateratiooflargetosmallparticles.

(14)

Fig.15–WeartracksofA357alloyanditsDPSCompositesataloadof30N,slidingvelocityof2.5m/sandslidingdistance of1500msubjectedtovaryingAgingtemperatures.Where(a)&(b)A357alloyatagingtemperaturesof180^◦Cand200^◦C,(c)

&(d)DPS1Compositeatagingtemperaturesof180^◦Cand200^◦C,(e)&(f)DPS2compositeatagingtemperaturesof180^◦C and200^◦C,(g)&(h)DPS3Compositeatagingtemperaturesof180^◦Cand200^◦C.Markings1–6representdelaminated wear-outarea,abrasion,thinploughedtrenches,deepploughedtrenches,craters,andslidingdirectionrespectively.

Worn surface of A357alloy atdifferent aging temperatures(180^◦Cand200^◦C)isshown inFig. 15(a)and (b).Itis observedthat wearmechanismchanges withtemperature.

At peak aging temperature, 180^◦C, wear is predominantly caused bythe surface delamination. When temperature is increasedto 200^◦C,instead of surface delamination, deep groovesareobservedwhichisanindicationofplasticdefor- mation.So,athightemperatures,wearmechanismchanges fromsurfacedelaminationtointenseplasticdeformationand materialremoval.Boththewornsurfacesshowwideandpar- allelgroovesrunninginslidingdirectionwithlargecavitiesin betweenthem.Theformationofcavitiescanbeattributedto delaminationofsurfacematerialofthealloy.Atahighload

of30N,thesofteningofsurfacetakesplaceduetofrictional resistanceasaresultofsurfacematerialofthealloygetting weldedtothecounterfacesurface.Duetoincreaseinadhesive natureofpinandalloy,delaminationoccurseasily.Itappears thattheextentofdelaminationishigherincaseof200^◦Caged alloywhichmaybeduetoitslowhardnesswhencompared tothatof180^◦Cagingcondition.

TheextentofdelaminationappearstobelessinDPS1com- positecomparedtothatofthealloyasseeninFig.15(c)and (d).HardSiCparticlesinDPS1compositeprotrudeoutofcom- positesurfaceduringweartesting processand avoiddirect contactbetweencompositesurfaceandcounterfacesurface.

Duetothis,theextentofdelaminationisdecreased.

(15)

ThewornsurfaceofDPS2compositeisnearlysmoothfor bothagingtemperaturesasshowninFig.15(e)and(f).Thisis mainlyduetopresenceofhigherweightfractionoflargesize SiCparticleswhichtendtotakemostoftheappliedloadand protectsmallsizedSiCparticlesaswellasthematrix[73,74].

Theselargeparticlesavoiddirectcontactbetweenthecounter- facesurfaceandcompositesurfacewhichiswhythegroove widthissmaller whencomparedtothatofA357alloyand othertwocomposites.

Ontheotherhand,thewornsurfaceofDPS3compositewas almostsimilartothatofDPS1composite.Deformationgrooves anddelaminationweretheprimaryreasonsofweightlossin thiscomposite.ThewornsurfaceofDPS3compositeattwo agingtemperaturesof180^◦Cand200^◦CasshowninFig.15(g) and(h) showchangesinthedeformationmechanismfrom delaminationat180^◦Cagingtemperaturetodeformationat 200^◦Cagingtemperature.

3.11. Three-dimensionalsurfacetopographiesofworn surfaceA357alloyanditsDPScompositesatvarying agingtemperatures

Three-dimensionalsurfacetopographiesofthewornsurface ofA357alloyanditsDPScompositestakenataloadof30N, slidingvelocityof2.5m/sandslidingdistanceof1500mare showninFig.16(a)–(h).IncaseofA357alloy,it canbeseen fromFig.16(a)and(b)thatthesurfaceshowedfeaturesofsur- facedelaminationandformationofdeepgroovessupporting theevidenceobtainedusingSEM(asshowninFig.15(a)and (b)).FurthercomparedtoaRavalueof8.00␮mat180^◦Caging temperaturethealloyagedat200^◦CshowedhigherRavalueof 8.44␮m.LowestRavaluesof2.60and2.71␮mwereobtained atagingtemperatureof180and200^◦CforDPS2composite.

Theseobservationsarewellinlinewiththelowspeciﬁcwear rateobtainedforthiscomposite.Further,comparedtoA357

Fig.16–Three-dimensionalsurfacetopographiesofthewornsurfaceofA357alloyanditsDPScompositesataloadof30N, slidingvelocityof2.5m/sandslidingdistanceof1500msubjectedtovaryingagingtemperatures.Where(a)&(b)A357alloy atagingtemperaturesof180^◦Cand200^◦C,(c)&(d)DPS1compositeatagingtemperaturesof180^◦Cand200^◦C,(e)&(f)DPS2 compositeatagingtemperaturesof180^◦Cand200^◦C,(g)&(h)DPS3compositeatagingtemperaturesof180^◦Cand200^◦C.

(16)

Fig.17–WeardebrisofA357alloyanditsDPSCompositesataloadof30N,slidingvelocityof2.5m/sandslidingdistance of1500msubjectedtovaryingagingtemperatures.Where(a)&(b)A357alloyatagingtemperaturesof180^◦Cand200^◦C,(c)

&(d)DPS1compositeatagingtemperaturesof180^◦Cand200^◦C,(e)&(f)DPS2compositeatagingtemperaturesof180^◦C and200^◦C,(g)&(h)DPS3compositeatagingtemperaturesof180^◦Cand200^◦C.Markings1–5representﬂeck-likedebris, ﬁber-likedebris,ruptureddebris,ribbeddebrisandcoillikedebrisrespectively.

alloyandothercompositestheundulationsobservedonworn surfaceofDPS2issigniﬁcantlyless(seeFig.15(e)and(f)).Also, comparedtoA357alloy,theDPScompositesshowedlesserRa valueswhichisattributedtoresistanceofferedbydualsize SiCparticles.Theasperitiesofcounterfacesurfacearepre- ventedfrompenetratinginsidethematrixbytheSiCparticles duetowhich thesurfaceroughnessvaluesare quitelesser forDPS composites. Unlike in several works [75,76] where thecompositesshowedgreaterundulationsascomparedto alloy,hereinthisworknosuchobservationsweremade.The depthofvalleysandwidthofgrooveswerefoundtobehigher forA357alloycomparedtothatofDPScomposites.Thisis mainlybecauseofhigherhardnessvaluesforDPScomposites

ascomparedtoA357alloy.Overalltheseresultsarewellinline withprecedingsub-sections(3.9and3.10).Further,compared toDPScompositesA357alloyexhibitedhigherRavaluesdue tohigherwearrate.Alongwiththisthesurfacetopographies ofDPScompositesshowednoabnormaldepth inthe worn surfaceindicatingabsenceofpull-outofSiCparticles.

3.12. WeardebrisanalysisofA357alloyanditsDPS compositesatvaryingagingtemperature

WeardebriswascollectedfrombothA357alloyanditsDPS composites after 180^◦C and 200^◦C aging temperatures for a ﬁxed load of30N,sliding velocity of2.5m/s and sliding

(17)

distanceof1500m.InthecaseofA357alloythesizeofwear debriscollectedfor180^◦Cwasmuchsmaller(∼300␮m)than thatcollectedfor200^◦C(∼600␮m)whichisshowninFig.17(a) and(b).InthecaseofDPS1compositethesizeofweardebris showedsimilartrendasthatofA357alloy.Weardebrissizeof

∼100␮mand∼180␮mwasobtainedforthecompositeaged at180^◦Cand200^◦CrespectivelyasshowninFig.17(c)and(d).

Ontheotherhand,DPS2compositeweardebrisasshownin Fig.17(e)and(f)havesizesapproximately∼50␮mand100␮m forthecompositesagedat180^◦Cand200^◦Crespectively.The weardebrissizeofDPS2compositeisverysmallwhencom- paredtothatofA357alloyandothertwocomposites.Most ofthedebrishadirregularﬂakelikemorphologywithsharp edgesindicatingdelaminationasprimarywearmechanism.

Thesmall sizeofwear debriscan beattributedto highest hardnessofDPS2composite forall casesofaging temperature.Similarly,forDPS3composite,weardebrishasasize of150␮mand 200␮mapproximately forthe samplesaged at180^◦Cand200^◦C respectivelyasshown inFig. 17(g)and (h).TheweardebrissizeandmorphologyofDPS3composites isalmostsameforboththeagingtemperaturesasshownin Fig.17(g)and(h).Overallitcanbeobservedthatatpeakaging temperatureof180^◦C,bothA357alloyand DPScomposites showedsmallerweardebrissizewhich isattributedtothe presenceofuniformlydispersedhardeningphasessuchas␤ and␤-Mg2Siprecipitatescomparedtotheoveragedcondition.

3.13. EffectofratioofDPSparticlesonmechanicaland wearpropertiesofDPScomposites

ItiswellknownthatDPScompositesshowbettermechani- calandwearpropertiescomparedtosingleparticlereinforced composites.DPScompositeshavebothsmallsizeandlarge sizeparticles invaryingproportion.However,it isnotclear whatshouldbeagood proportionoflargeand smallsized particlesthatwouldgiveoptimummechanicalandwearprop- erties.Thisquestion hasnotbeenstudiedinearlierworks.

Fromthiswork,itwasfoundthatsmallsizedparticlesaregood forstrengthpropertieswhilelargesizedparticlesaregoodfor hardnessandwearproperties.

FromFig.10(a) and(b)weseethathigh YSandUTSare realizedwhen small sized particle proportion ishigher (at L:S=0.5).Ductilityalsoshowssimilartrendasthatofstrength (referFig.11)anditisbetterwhenthecompositehashigher proportionofsmallparticles(atL:S=0.5).However,goodhard- nessandwearpropertiesareobtainedwhentheproportionof largeparticlesishigher(L:S=2)asshowninFigs.13and14.As explainedinpervioussections,goodhardnessandwearprop- ertiesaremainlyduetolargesizedparticlestakingtheload andhence compositeswithhigherratioofL:Saregood for wearproperties.Whereas,strengthandductilityaremainly theresultofdislocationpinningandbowingwhicharegood whenparticlesizeissmaller.Hencesmallerparticlesaregood forstrengthproperties.

4. Conclusions

Thefollowingconclusionsweredrawnfromthepresentwork:

1. MechanicalandwearpropertiesofA357compositerein- forced with dual size SiC particles were studied after agingatvarying temperatures((540^◦C-6H-160^◦C,540^◦C- 6H-180^◦Cand540^◦C-6H-200^◦C)).

2. Microscopyanalysisshowed fairlyuniformdispersionof dualsizeSiCparticlesinA357matrix.

3. FromthedensitymeasurementsofA357alloyanditsDPS compositesatvaryingtemperaturesitcanbeconcluded thatthedispersionofSiCparticleswasfoundtobegood withalmostnoobservableporosityoranycastingdefects.

4. TEManalysisshowedtheformationof␤”-semi-coherent phaseandMg2Siprecipitate(␤-phase)alongwithSiCparti- cles.Thesephasesleadtotheimprovementinmechanical

&wearpropertiesinbothA357alloyanditsDPScompos- ites.

5. Allthecomposites(DPS1,DPS2andDPS3)showedimprove- mentinmechanicalandwearpropertieswhencompared toA357alloy.

6. Overall,itcanbeconcludedthatforthesametotalweight percentageofSiCreinforcement,ratiooflargetosmallpar- ticlesinﬂuencesmechanicalandwearproperties.Higher proportionofsmallerparticlesimprovestrengthandduc- tilitywhereas,higherproportionoflargerparticlesimprove hardnessandwearproperties.

Conﬂicts of interest

Theauthorsdeclarenoconﬂictsofinterest.

references

[1]KumarRV,KeshavamurthyR,PeruguCS,KoppadPG,Alipour M.Inﬂuenceofhotrollingonmicrostructureand

mechanicalbehaviourofAl6061-ZrB2in-situmetalmatrix composites.MaterSciEngA2018;738:344–52.

[2]MirjavadiSS,etal.EffectofhotextrusionandT6heat treatmentonmicrostructureandmechanicalpropertiesof Al-10Zn-3.5Mg-2.5Cunanocompositereinforcedwith graphenenanoplatelets.JManufProcess2018;36:264–71.

[3]SethuramD,KoppadPG,ShettyH,AlipourM,KordS.

CharacterizationofgraphenereinforcedAl-Sn nanocompositeproducedbymechanicalalloyingand vacuumhotpressing.MaterTodayProc2018;5(11):24505–14.

[4]MirjavadiSS,etal.Effectofmulti-passfrictionstir processingonthemicrostructure,mechanicalandwear propertiesofAA5083/ZrO2nanocomposites.JAlloysCompd 2017;726:1262–73.

[5]CeschiniL,MorriA,MorriA,GamberiniA,MessieriS.

Correlationbetweenultimatetensilestrengthand solidiﬁcationmicrostructureforthesandcastA357 aluminiumalloy.MaterDes2009;30(10):4525–31.

[6]WangQ,DavidsonC.Solidiﬁcationandprecipitation behaviourofAl-Si-Mgcastingalloys.JMaterSci 2001;36(3):739–50.

[7]TanY-H,LeeS-L,LinY-L.EffectsofBeandFeadditionson themicrostructureandmechanicalpropertiesofA357.0 alloys.MetallMaterTransA1995;26(5):1195–205.

[8]EdwardsG,StillerK,DunlopG,CouperM.Theprecipitation sequenceinAl–Mg–Sialloys.ActaMater

1998;46(11):3893–904.

(18)

[9]WangQ.Microstructuraleffectsonthetensileandfracture behaviorofaluminumcastingalloysA356/357.MetallMater TransA2003;34(12):2887–99.

[10]CanakciA,VarolT,NazikC.Effectsofamountofmethanol oncharacteristicsofmechanicallyalloyedAl-Al2O3

compositepowders.MaterTechnol2012;27:320–7.

[11]CanakciA,VarolT,ErtokS.Theeffectofmechanicalalloying onAl₂O₃distributionandpropertiesofAl₂O₃particle reinforcedAl-MMCs.SciEngCompos2012;19:227–35.

[12]CanakciA,VarolT.Anovelmethodfortheproductionof metalpowderswithoutconventionalatomizationprocess.J CleanProd2015;99:312–9.

[13]CanakciA,ArslanF,VarolT.Physicalandmechanical propertiesofstircastingprocessedAA2024/B4Cp composites.SciEngComposMater2014;21:505–15.

[14]CanakciA,ArslanF,VarolT.Effectofvolumefractionand sizeofB4Cparticlesonproductionandmicrostructure propertiesofB4Creinforcedaluminumalloycomposites.

MaterSciTechnol2013;29:954–60.

[15]CanakciA,OzsahinS,VarolT.Predictionofeffectof reinforcementsizeandvolumefractionontheabrasivewear behaviorofAA2014/B4CpMMCsusingartiﬁcialneural network.ArabJSciEng2014;39:6351–61.

[16]ZulﬁaA,AtkinsonHV,JonesH,KingS.Effectofhotisostatic pressingoncastA357aluminiumalloywithandwithoutSiC particlereinforcement.JMaterSci1999;34:4305–10.

[17]BadiziRM,Askari-PaykaniM,ParizadA,ShahverdiHR.

EffectsofelectromagneticfrequencyandSiCnanoparticles onthemicrostructurereﬁnementandmechanicalproperties ofAlA357-1.5wt%SiCnanocomposites.IntJMetalCast 2018;12:565–73.

[18]DattaJ,DattaS,BanerjeeMK,BandyopadhyayS.Effectof scandiumadditiononthecorrosionbehaviorof

Al–Si–Mg–SiCpmetalmatrixcomposites.Composites:PartA 2004;35:1003–8.

[19]YuB,ZhangYJ,ZhaoZ,ZhaoF,CaiQ,LiuC.Thereinforcing mechanismofTiB2inTiB2/A357composite.ActaMetallSin EnglLett2009;16(5):375–8.

[20]KandemirS.Microstructureandmechanicalpropertiesof A357/SiCnanocompositesfabricatedbyultrasonic cavitation-baseddispersionofball-millednanoparticles.J ComposMater2017;51(3):395–404.

[21]LeonardA,PerrinC,RainforthW.Microstructuralchanges inducedbydryslidingwearofaA357/SiCmetalmatrix composite.MaterSciTechnol1997;13(1):41–8.

[22]BloyceA,SummersJ.Staticanddynamicpropertiesof squeeze-castA357-SiCparticulateDuralcanmetalmatrix composite.MaterSciEngA1991;135:231–6.

[23]TaghiabadiR,MahmoudiM,EmamyGhomyM,CampbellJ.

Effectofcastingtechniquesontensilepropertiesofcast aluminiumalloy(Al–Si–Mg)andTiB2containingmetal matrixcomposite.MaterSciTechnol2003;19(4):497–502.

[24]ZhangLJ,QiuF,WangJ-G,WangH-Y,JiangQ-C.

MicrostructuresandmechanicalpropertiesoftheAl2014 compositesreinforcedwithbimodalsizedSiCparticles.

MaterSciEngA2015;637:70–4.

[25]BindumadhavanP,WahHK,PrabhakarO.Dualparticlesize (DPS)composites:effectonwearandmechanicalproperties ofparticulatemetalmatrixcomposites.Wear

2001;248(1–2):112–20.

[26]AroraR,KumarS,SinghG,PandeyO.Inﬂuenceofparticle sizeandtemperatureonthewearpropertiesof

rutile-reinforcedaluminiummetalmatrixcomposite.J ComposMater2015;49(7):843–52.

[27]ZhangQ,WuG,SunD,ChenG,JiangL.Microstructureand thermalconductionpropertiesofanAl-12Simatrix compositereinforcedwithdualsizedSiCparticles.JMater Sci2004;39(1):303–5.

[28]SharmaS,NandaT,PandeyO.Effectofdualparticlesize (DPS)ondryslidingwearbehaviourofLM30/sillimanite composites.TribolInt2018;123:142–54.

[29]YangMJ,ZhangDM,GuXF,ZhangLM.EffectsofSiCparticle sizeonCTEsof/Alcompositesbypulsedelectriccurrent sintering.MaterChemPhys2006;99:170–3.

[30]AvinashL,RamprabhuT,BonthaS.TheEffectonthedry slidingwearbehaviorofgravitycastA357reinforcedwith dualsizesiliconcarbideparticles.ApplMechMater 2016;829:83–9.

[31]LakshmikanthanA,BonthaS,KrishnaM,KoppadPG, RamprabhuT.Microstructure,mechanicalandwear propertiesoftheA357compositesreinforcedwithdualsized SiCparticles.JAlloysCompd2019;786:570–80.

[32]ApelianD,ShivkumarS,SigworthG.Fundamentalaspectsof heattreatmentofcastAl-Si-Mgalloys.AFSTrans

1989;97:727–42.

[33]ShivkumarS,KellerC,TrazzeraM,ApelianD.Precipitation hardeninginA356alloys.In:Production,reﬁning,fabrication andrecyclingoflightmetals.Elsevier;1990.p.264–78.

[34]HandbookA.Heattreating.ASMInt1991;4(10).

[35]AjithKumarKK,ViswanathA,RajanTPD,PillaiUTS,PaiBC.

Physical,mechanical,andtribologicalattributesofstir-cast AZ91/SiC_pcomposite.ActaMetallSin(EnglLett)

2014;27:295–305.

[36]PrasadaDS,ShobabC,RamanaiahN.Investigationson mechanicalpropertiesofaluminumhybridcomposites.J MaterResTechnol2014;3(1):79–85.

[37]HuY,WuT,GuoY,WangW,SongM,QianL,etal.Effectsof T6treatment,tensiletemperature,andmassfractionofSiC onthemechanicalpropertiesofSiCp/6061Alcomposites.

Materials2019;12:1602.

[38]RaoC,SelvarajN,VeereshkumarG.Studiesonmechanical anddryslidingwearofAl6061–SiCcomposites.ComposB Eng2012;43(3):1185–91.

[39]T.RamPrabhu,M.Murugan,B.P.Chiranth,R.K.Mishra,N.

Rajini,P.Marimuthu,P.DineshBabu,G.SuganyaEffectsof Dual-PhaseReinforcementParticles(FlyAsh+Al2O3)onthe WearandTensilePropertiesoftheAA7075AlAlloyBased Composites.

[40]AversaA,LorussoM,TrevisanF,AmbrosioEP,CalignanoF, ManfrediD,etal.Effectofprocessandpost-process conditionsonthemechanicalpropertiesofanA357alloy producedvialaserpowderbedfusion.Metals2017;7(2):68.

[41]AkhterR,IvanchevL,BurgerH.Effectofpre/postT6heat treatmentonthemechanicalpropertiesoflaserweldedSSM castA356aluminiumalloy.MaterSciEngA

2007;447(1–2):192–6.

[42]MaubeSE,WangombeDN,MarangaSM,KihiuJM.Effectof coolingrateandheattreatmentonthemicrostructureand impactresistanceofrecycledaluminiumsandcastalloy.J SustainResEng2014;1(1).

[43]CottuJP,CoudercJJ,ViguierB,BernardL.InﬂuenceofSiC reinforcementonprecipitationandhardeningofametal matrixcomposite.JMaterSci1992;27:3068–74.

[44]Yamano ˘gluR,KarakulakE,ZerenA,ZerenM.Effectofheat treatmentonthetribologicalpropertiesof

Al–Cu–Mg/nanoSiCcomposites.MaterDes2013;49:820–5.

[45]MyriounisD,HasanS,MatikasT.Heattreatmentand interfaceeffectsonthemechanicalbehaviorofSiC-particle reinforcedaluminiummatrixcomposites.JASTMInt 2008;5(7):1–10.

[46]ChristmanT,SureshS.Microstructuraldevelopmentinan aluminumalloy-SiCwhiskercomposite.ActaMetall 1988;36(7):1691–704.

[47]ManoharanM,LewandowskiJ.In-situdeformationstudiesof analuminummetal-matrixcompositeinascanning electronmicroscope.ScrMetall1989;23(10):1801–4.

(19)

[48]KaruppusamyT,VelmuruganC,Thirumalaimuthukumaran M.Experimentalstudyonthemechanicalpropertiesofheat treatedaluminiumcomposites.MaterResExpress

2019;6:096552.

[49]SjolanderE,SeifeddineS.TheheattreatmentofAl–Si–Cu–Mg castingalloys.JMaterProcessTechnol2010;210(10):1249–59.

[50]LiB,LuoB,HeK,ZengL,FanW,BaiZ.Effectofagingon interfacecharacteristicsofAl–Mg–Si/SiCcomposites.JAlloys Compd2015;649:495–9.

[51]LiuC,MaP,ZhanL,HuangM,LiJ.SoluteSn-induced formationofcomposite␤/␤precipitatesinAl-Mg-Sialloy.

ScrMater2018;155:68–72.

[52]WangT,ZhaoY,ChenZ,ZhengY,KangH.Thebimodaleffect ofLaonthemicrostructuresandmechanicalpropertiesof in-situA356–TiB2composites.MaterDes2015;85:724–32.

[53]ArsenaultR,EverettR.Tensileandcompressivepropertiesof metalmatrixcomposites4.AcademicPress;1991.

[54]GaneshV,ChawlaN.Effectofparticleorientationanisotropy onthetensilebehaviorofmetalmatrixcomposites:

experimentsandmicrostructure-basedsimulation.Mater SciEngA2005;391(1–2):342–53.

[55]MirjavadiSS,etal.InﬂuenceofTiO2nanoparticles

incorporationtofrictionstirwelded5083aluminumalloyon themicrostructure,mechanicalpropertiesandwear resistance.JAlloysCompd2017;712:795–803.

[56]CaiC,GengH,WangS,GongB,ZhangZ.Microstructure evolutionofAlSi10Mg(Cu)alloyrelatedtoisothermal exposure.Materials2018;11(5):809.

[57]BembalgeO,PanigrahiS.Developmentandstrengthening mechanismsofbulkultraﬁnegrainedAA6063/SiCcomposite sheetswithvaryingreinforcementsizerangingfromnanoto microdomain.JAlloysCompd2018;766:355–72.

[58]UmaruO,AbdulwahabM,TokanA,BelloA,UmarH.Effectof doublethermalageingtreatmentonthemechanical propertiesofAl–Cu–Mg/3%ricehuskashcomposite.Results Phys2016;6:342–5.

[59]ZhuH,GuoJ,JiaJ.Correlationoftheagingcharacteristics anddeformationbehaviorofA357alloy.JMaterEngPerform 2001;10(2):186–91.

[60]PrabhuTR.Effectsofageingtimeonthemechanicaland conductivitypropertiesforvariousroundbardiametersof AA2219Alalloy.EngSciTechnolIntJ2017;20(1):133–42.

[61]ChenZ,HaoX,WangY,ZhaoK.In-situobservationoftensile fractureinA357castingalloys.JMaterSciTechnol

2014;30:139–45.

[62]SharmaV,KumarS,PanwarRS,PandeyO.Microstructural andwearbehaviorofdualreinforcedparticle(DRP) aluminumalloycomposite.JMaterSci2012;47(18):6633–46.

[63]RavikumarM,ReddappaH,SureshR.Studyonmechanical andtribologicalcharacterizationofAl2O3/SiCpreinforced aluminummetalmatrixcomposite.Silicon

2018;10(6):2535–45.

[64]PrabhuTR.Effectofbimodalsizeparticlesreinforcementon thewear,frictionandmechanicalpropertiesofbrake composites.Tribol–MaterSurfInterfaces2016;10(4):

163–71.

[65]RaoR,DasS,MondalD,DixitG.Dryslidingwearbehaviour ofcasthighstrengthaluminiumalloy(Al–Zn–Mg)andhard particlecomposites.Wear2009;267(9–10):1688–95.

[66]RajeevV,DwivediD,JainS.Effectofloadandreciprocating velocityonthetransitionfrommildtoseverewearbehavior ofAl–Si–SiCpcompositesinreciprocatingconditions.Mater Des2010;31(10):4951–9.

[67]ChungS,HwangBH.Amicrostructuralstudyofthewear behaviourofSiCp/Alcomposites.TribolInt1994;27(5):

307–14.

[68]ChawlaKK.Metalmatrixcomposites.MaterSciTechnol 2006.

[69]SongW,KrauklisP,MouritzA,BandyopadhyayS.Theeffect ofthermalageingontheabrasivewearbehaviourof age-hardening2014Al/SiCand6061Al/SiCcomposites.Wear 1995;185(1–2):125–30.

[70]PedersenL,ArnbergL.Theeffectofsolutionheattreatment andquenchingratesonmechanicalpropertiesand

microstructuresinAlSiMgfoundryalloys.MetallMaterTrans A2001;32(3):525–32.

[71]GuanLY,LiBL,QiP,WeiLJ,NieZR.Effectofheattreatment onthemicrostructureandpropertyofAl-Si-Mgalloy.Mater SciForum2016;850:768–72.

[72]ChackoM,NayakJ.Agingbehaviourof6061Al-15Vol%SiC compositeinT4andT6treatments.IntJChemMolNucl MaterMetallEng2014;8(3):195–8.

[73]RajmohanT,PalanikumarK,RanganathanS.Evaluationof mechanicalandwearpropertiesofhybridaluminiummatrix composites.TransNonferrousMetSocChina

2013;23(9):2509–17.

[74]SinghJ,ChauhanA.Overviewofwearperformanceof aluminiummatrixcompositesreinforcedwithceramic materialsundertheinﬂuenceofcontrollablevariables.

CeramInt2016;42(1):56–81.

[75]SardarS,KarmakarSK,DasD.TribologicalpropertiesofAl 7075alloyand7075/Al₂O₃compositeundertwo-body abrasion:astatisticalapproach.JTribol2018;140:051602.

[76]SardarS,PradhanSK,KarmakarSK,DasD.Modelingof abradedsurfaceroughnessandwearresistanceof aluminummatrixcomposites.JTribol2019;141:0716.