Aluminum alloys Table of Contents1 Aluminum Alloys:..........................................................................................................................32 Types of aluminum alloys...............................................................................................................33 Cast aluminum Alloys:...................................................................................................................34 Heat treatment of cast aluminum alloys.........................................................................................44.1 Heat treatable alloy..................................................................................................................44.2 Non heat treatable cast alloys..................................................................................................45 Effect of Alloying Elements:..........................................................................................................4.1 Copper !Cu" 2###:...................................................................................................................4.1.1 Commercial alloys of 2### series....................................................................................$.2 %anganese !%n" 3###.............................................................................................................$.2.1 Commercial alloys of 3###..............................................................................................&.3 'ilicon !'i" 4###......................................................................................................................&.4 %agnesium !%g" ###............................................................................................................(.4.1 Commercial Al)%g alloys................................................................................................*. %agnesium an+ 'ilicon !%g2'i" $###....................................................................................*..1 %agno# Commercial alloys of $###..............................................................................1,.$ -inc !-n" ##.......................................................................................................................1,.& .thers elements (###............................................................................................................11.&.1 /ron !0e"..........................................................................................................................11.&.2 Chromium !Cr"...............................................................................................................11.&.3 Nic1el !Ni"......................................................................................................................11.&.4 Titanium !Ti"..................................................................................................................12.&. -irconium !-r"...............................................................................................................12.&.$ 2ithium !2i"....................................................................................................................12.&.& 2ea+ !3b" an+ 4ismuth !4i"...........................................................................................12$ Cast Aluminum Alloys.................................................................................................................12Foundry EngineeringPage 1Aluminum alloys $.1 Classifications of Cast Aluminum Alloys.............................................................................13& Effect of alloying a++ition...........................................................................................................14&.1 Aluminum)copper alloys 2##.#:............................................................................................14&.1.1 Commercial Al)Cu cast alloy.........................................................................................14&.2 Aluminum)'ilicon alloy 5ith copper an+ magnesium 3##.#................................................14&.3 4inary aluminum)silicon alloys 4##.#..................................................................................14&.3.1 E#ample Al)'i cast alloy................................................................................................1&.4 Aluminum)%agnesium alloy ##.#......................................................................................1&.4.1 Commercial Al)%g cast alloy........................................................................................1&. Aluminum)-inc alloy #.#..................................................................................................1&..1 Commercial Al)-n alloy................................................................................................1&.$ Aluminum)Tin alloy (##.#....................................................................................................1$&.$.1 Commercial Al)Ti alloy.................................................................................................1$( 'ome common casting alloys an+ their properties:.....................................................................1$Foundry EngineeringPage 2Aluminum alloys 1 Aluminum Alloys:Aluminum the most secon+ plentiful metallic element on earth became an economic competitor inengineering applications as recently as the en+ of the 1*th century./t 5as to become a metal for itstime.0or the most important in+ustrial +e6elopment 5oul+7by +eman+ing material characteristicconsistent 5iththeuni8ue8ualitiesof aluminuman+itsalloys. 9reatlybenefitsgro5thinthepro+uction an+ use of ne5 metal. 2 Types of aluminum alloys Aluminum alloys are alloys in 5hich aluminum !Al" is the pre+ominant metal. The typical alloyingelements are copper7 magnesium7 manganese7silicon an+ :inc. There are t5o principalclassifications. Namely 1. casting alloys 2. 5rought alloys 4oth of 5hich are further sub+i6i+e+ into the categories heat)treatable an+ non)heat)treatable. About(; of aluminum is use+ for 5rought pro+ucts7 for e#ample rolle+ plate7 foils an+ e#trusions. Castaluminum alloys yiel+ cost)effecti6e pro+ucts +ue to the lo5 melting point7 although they generallyha6e lo5er tensile strengths than 5rought alloys. The most important cast aluminum alloy systemis Al1? The main alloying elements in the AA system are as follo5s. 1##.# series are minimum **; aluminum 2##.# series copper 3##.# series silicon7 copper an+@or magnesium 4##.# series silicon ##.# series magnesium #.# series :incFoundry EngineeringPage 3Aluminum alloys (##.# series tin *##.# other elements4 Heat treatment of cast aluminum alloys Ahen the term is applie+ to aluminum alloys7 ho5e6er7 its use fre8uently is restricte+ to the specificoperations employe+ to increase strength an+ har+ness of the precipitation har+enable 5rought an+cast alloys. Heat treatable alloy Non heat treatable alloy4.1 Heat treatable alloyAluminum alloy of this type belongs to system 5ith limite+ solubility in soli+ solution. These areprecipitate+har+enablealloy. Themaincharacter of thistypeof alloysystemisatemperature+epen+ent e8uilibrium soli+ solubility7 5hich increase 5ith increase in temperatue.in a++ition otherre8uirements are retaining single phase supersaturate+ solution by 8uenching an+ coherent state.E#amples of this group is 2### Al)Cu alloy an+ Al)Cu)%g alloy. $### series inclu+e Al)-n7 Al)-n)%g alloy ## series inclu+e Al)-n7 Al)-n)%g)Cu type alloys4.2 Non heat treatable cast alloysThese alloys +o not respon+ to heat treatment because these alloys consist of homogeneous soli+solution 5ith or 5ithout non)coherent precipitate an+ sho5 lo5 strength an+ high +uctility. 3ure aluminum !11,,"7 Al)%n !3,,3" ### Al)%g alloys $### Al)'i alloys5 Eect of Alloyin! Elements:5.1 Copper "Cu# 2$$$:The aluminum)copper alloys typically contain bet5een 2 to 1,; copper7 5ith smaller a++itions ofother elements. The copper pro6i+essubstantialincreasesinstrengthan+ facilitates precipitationhar+ening. The intro+uctionof copper toaluminumcanalsore+uce +uctilityaBn+corrosionresistance. Thesusceptibilitytosoli+ificationcrac1ingof aluminum)copper alloys isincrease+Cconse8uently7someofthesealloyscanbethemostchallengingaluminumalloysto5el+.Thesealloys inclu+esomeof thehighest strengthheat treatablealuminumalloys. Themost commonapplications for the 2### series alloys are aerospace7 military 6ehicles an+ roc1et fins.Foundry EngineeringPage 4Aluminum alloys The ma#imum solubility of copper in aluminum is .$; at 1,1(o0.Figure 1: Al-Cu phase diagramThis is full phase +iagram of aluminum an+ copper but useful portion is only up to 1,; of copper.0rom2).$;ofcopperismostlyuse+forheat treatment purposes. Thetheta!D"phaseisaninterme+iatealloyphase5hosecom)positioncorrespon+scloselytothecompoun+CuAl2.Thesealloys may contain smaller amounts of silicon7 iron7 magnesium7 manganese7 chromium7 an+ :inc. Table 1 phases present in Al-Cu phase diagram of heat treatable portion5.1.1Commercial alloys of 2$$$ series The three most 5i+ely use+ 5rought aluminum)copper alloys are 2,147 2,1&7 an+ 2,24.Foundry EngineeringPage 51Aluminum alloys 5.1.1.1 %uralumin 2&1' Al(Cu alloyThe ol+est of all the heat treatable aluminum alloys is +uralumin !2,1&" containing 4 percent copper.This alloy is 5i+ely use+ for ri6ets in aircraft construction. 'ince this is a natural)aging alloy7 aftersolutiontreatment it isrefrigerate+topre6ent aging. Asasinglephase7 inthe'olutiontreate+con+ition7 it has goo+ +uctility so that the ri6et hea+ may be easily forme+. 'ubse8uent return of thematerial to room temperature causes precipitation of the D phase as small submicroscopic particles7increasing the har+ness an+ strength.5.1.1.2 2&14 Al(Cu alloyAlloy 2,14 has higher copper an+ manganese content than 2,1& an+ is susceptible to artificial aging./n the artificially age+ temper7 2,14 has a higher tensile strength7 much higher yiel+ strength7 an+lo5er elongation than 2,1&. This alloy is use+ for hea6y)+uty forgings7 aircraft fittings7 an+ truc1frames.5.1.1.3 2&24 Al(Cu alloyAlloy2,247 containing 4.percent copper an+1. percent magnesium7 +e6elops the higheststrengthsofanynaturallyage+aluminum)copper typeof alloy. Thehigher magnesiumcontent7compare+ 5ith 2,1&7 ma1es it more +ifficult to fabricate.A combination of strain har+ening an+aging 5ill +e6elop the ma#imum yiel+ strength attainable in high)strength alloy sheet. Typical usesof 2,24 alloy are aircraft structures7 ri6ets7 har+5are7 truc1 5heels an+ scre5)machine pro+ucts5.2 )an!anese ")n# 3$$$The a++ition of manganese to aluminum increases strength some5hat through solution strengtheningan+ impro6es strain har+ening 5hile not appreciably re+ucing +uctility or corrosion resistance. Figure 2: Al-Mn phase diagramFoundry EngineeringPage 6Aluminum alloys These are mo+erate strength non)heat treatable materials that retain strength at ele6ate+ temperaturesan+ are sel+om use+ for maEor structural applications.The most commonapplications for the 3###series alloys are coo1ingutensils7 ra+iators7 aircon+itioning con+ensers7 e6aporators7 heat e#changers an+ associate+ piping systems. . Thema#imum solubility of manganese in the soli+ solution is 1.(2 at the eutectic temperature of 121$,0.4ecause of the limite+ solubility7 manganese is not use+ as a maEor alloying element in any castingalloys an+ is use+ in only a fe5 5rought alloys.5.2.1Commercial alloys of 3$$$ .ne of the alloys in this group is the popular 3,,3 alloy7 5hich has goo+ formability7 6ery goo+resistance to corrosion7 an+ goo+ 5el+ability. Typical applications are utensils7 foo+ an+ chemicalhan+ling an+ storage e8uipment7 gasoline an+ oil tan17 pressure 6essels an+ piping. 5.3 *ilicon "*i# 4$$$ The a++ition of silicon to aluminum re+uces melting temperature an+ impro6es flui+ity. 'ilicon aloneinaluminumpro+uces anon)heat treatablealloyC ho5e6er7 incombination5ithmagnesiumitpro+uces a precipitation har+ening heat)treatable alloy. Conse8uently7 there are both heat)treatablean+ non)heat treatable alloys 5ithin the 4### series. 'ilicon a++itions to aluminum are commonlyuse+ for the manufacturing of castings. The most common applications for the 4### series alloys arefiller 5ires for fusion 5el+ing an+ bra:ing of aluminum. Figure 3: Al-Si phase diagramFoundry EngineeringPage 7Aluminum alloys The aluminum)rich portion of the aluminum silicon alloy system is sho5n. The ma#imum solubilityofsiliconinFsoli+solutionis1.$percentattheeutectictemperatureof1,&1o0. Althoughthesol6us line sho5s lo5er solubility at lo5er temperatures7 these alloys are generally not heat treatable.5.4 )a!nesium ")!# 5$$$ The a++ition of magnesium to aluminum increases strength through soli+ solution strengthening an+impro6estheirstrainhar+eningability. Thesealloysarethehighest strengthnonheat treatablealuminumalloysan+are7 therefore7 use+e#tensi6elyforstructural applications.The###seriesalloys are pro+uce+ mainly as sheet an+ plate an+ only occasionally as e#trusions. The reason forthis is that these alloys strain har+en 8uic1ly an+7 are7 therefore +ifficult an+ e#pensi6e to e#tru+e.Although the sol6us line7 sho5 consi+erable +ecrease in solubility 5ith +ecrease in temperature ofmagnesium in aluminum. 'ome common applications for the ### series alloys are truc1 an+ trainbo+ies7 buil+ings7 armore+ 6ehicles7 ship an+ boat buil+ing7 chemical tan1ers7 pressure 6essels an+cryogenic tan1s.Figure 4: Al-Mg phase diagram5.4.1Commercial Al()! alloysThe 5rought alloys are characteri:e+ by goo+ 5el+ability7 goo+ corrosion resistance7 an+ mo+eratestrength. Alloy ,, !,.( percent magnesium" is use+ for architectural e#trusions alloy ,, !1.2 percent magnesium" for tubing an+ automoti6e gas an+ oil linesFoundry EngineeringPage 8Aluminum alloys alloy ,(3 !4. percent magnesium" for marine an+ 5el+e+ structural applicationsC an+ alloy,$ !.2 percent magnesium" for insect screens7 cable sheathing7 an+ ri6ets for use 5ithmagnesium alloys.5.5 )a!nesium an+ *ilicon ")!2*i# ,$$$ Thea++ition of magnesium an+ silicon toaluminum pro+uces the compoun+magnesium)silici+e!%g2'i".The formation of this compoun+ pro6i+es the $### series their heat)treatability.The $###series alloys are easily an+ economically e#tru+e+ an+ for this reason are most often foun+ in ane#tensi6e selection of e#tru+e+ shapes. These alloys form an important complementary system 5iththe ### series alloy.Figure : Al-Mg2Si phase diagram !ith aluminum ri"h portionThe ### series alloy use+ in the form of plate an+ the $### are often Eoine+ to the plate in somee#tru+e+ form. 'omeofthe common applicationsforthe $### seriesalloys arehan+rails7 +ri6eshafts7 automoti6e frame sections7 bicycle frames7 tubular la5n furniture7 scaffol+ing7 stiffeners an+braces use+ on truc1s7 boats an+ many other structural fabrications.5.5.1)a!no$ Commercial alloys of ,$$$The 5rought alloys inclu+e $,37 $,$17 an+ $,$3 are mostly use+.5.5.1.1 ,&,1 Al()!2*i Construction of aircraft structures7 such as 5ings an+ fuselages7 more commonlyin homebuilt aircraft than commercial or military aircraft. Construction7 inclu+ing small utility boats. Automoti6e parts7 such as 5heel spacers. Aluminum cans for the pac1aging of foo+stuffs an+ be6erages.Foundry EngineeringPage 9Aluminum alloys 5.5.1.2 ,&53 Al()!2*i Aluminum $,3 alloy is chiefly use+ in the manufacture of ro+ an+ 5ire for ri6ets. /t is alsouse+ in se6eral col+ hea+ing applications7 5here it is use+ in the form of T)temper 5ire.5., -inc "-n# '$$$ The a++ition of :inc to aluminum !in conEunction 5ith some other elements7 primarily magnesiuman+@or copper" pro+uces heat)treatable aluminum alloys of the highest strength. The solubility of :incin aluminum is 31.$ percent at 2&o07 +ecreasing to .$ percent at 2&o0.Figure #: Al-$n phase diagram !ith aluminum ri"h portionCommercial 5rought alloys contain :inc7 magnesium7 an+ copper 5ith smaller a++itions ofmanganese an+chromium. The :inc substantiallyincreases strengthan+permits precipitationhar+ening.'ome of these alloys can be susceptible to stress corrosion crac1ing an+ for this reasonare not usually fusion 5el+e+..ther alloys 5ithin this series are often fusion 5el+e+ 5ith e#cellentresults.'ome of the common applications of the ## series alloys are aerospace7 armore+ 6ehicles7baseball bats an+ bicycle frames.5.' .thers elements /$$$This series inclu+e elements 5hich are rarely use+ in aluminum alloys. 'ome of these are impurityatoms 5.'.10ron "1e# /ron is the most common impurity foun+ in aluminum an+ is intentionally a++e+ to some pure !1###series" alloys to pro6i+e a slight increase in strength.Foundry EngineeringPage 10Aluminum alloys 5.'.2Chromium "Cr# Chromium is a++e+ to aluminum to control grain structure7 to pre6ent grain gro5th in aluminum)magnesium alloys7an+ topre6ent recrystalli:ation inaluminum)magnesium)silicon or aluminum)magnesium):inc alloys +uring heat treatment. Chromium5ill also re+uce stress corrosionsusceptibility an+ impro6es toughness.5.'.3Nic2el "Ni# Nic1el is a++e+toaluminum)copper an+toaluminum)siliconalloys toimpro6e har+ness an+strength at ele6ate+ temperatures an+ to re+uce the coefficient of e#pansion.5.'.4Titanium "Ti# Titanium is a++e+ to aluminum primarily as a grain refiner.The grain refining effect of titanium isenhance+ if boron is present in the melt or if it is a++e+ as a master alloy containing boron largelycombine+ as Ti42.Titanium is a common a++ition to aluminum 5el+ filler 5ire as it refines the 5el+structure an+ helps to pre6ent 5el+ crac1ing.5.'.5-irconium "-r# -irconiumisa++e+toaluminumtoformafineprecipitateofintermetallicparticlesthat inhibitrecrystalli:ation.5.'.,3ithium "3i# Thea++itionof lithiumtoaluminumcansubstantiallyincreasestrengthan+7 GoungHsmo+ulus7pro6i+e precipitation har+ening an+ +ecreases +ensity.5.'.'3ea+ "4b# an+ 5ismuth "5i# 2ea+ an+ bismuth are a++e+ to aluminum to assist in chip formation an+ impro6e machinability. Thesefreemachiningalloys areoftennot 5el+ablebecausethelea+an+bismuthpro+ucelo5melting constituents an+ can pro+uce poor mechanical properties an+@or high crac1 sensiti6ity onsoli+ification. 'ummary: There are many aluminum alloys use+ in in+ustry to+ay ) o6er 4,, 5rought alloys an+ o6er2,, casting allloys are currently registere+ 5ith the Aluminum Association.Certainly one ofthe most important consi+erations encountere++uring the 5el+ing of aluminumis thei+entification of the aluminum base alloy type to be 5el+e+./f the base material type of thecomponent to be 5el+e+ is not a6ailable through a reliable source7 it can be +ifficult to selecta suitable 5el+ing proce+ure.There are some general gui+elines as to the most probable typeof aluminum use+ in +ifferent applications7 such as those mentione+ abo6e. Ho5e6er7 it is6ery important to be a5are that incorrect assumptions as to the chemistry of an aluminumFoundry EngineeringPage 11Aluminum alloys alloy can result in 6ery serious effects on the 5el+ performance./t is strongly recommen+e+that positi6e i+entification of the type of aluminum is ma+e an+ that 5el+ing proce+ures be+e6elope+ an+ teste+ in or+er to 6erify 5el+ performance., Cast Aluminum AlloysAluminum casting alloys are the most 6ersatile of all common foun+ry alloys an+ generally ha6e thehighest castability ratings. Aluminum casting alloys are base+ on the same alloy systems as those of5rought aluminumalloys7are strengthene+by thesamemechanisms!5iththee#ceptionofstrainhar+ening"7an+ aresimilarly classifie+ into non)heat)treatable an+ heat)treatable types. The maEor +ifference is that thecasting alloys use+ in the greatest 6olumes contains alloying a++itions of silicon far in e#cess of thatfoun+!or use+" inmost 5rought alloys. Aluminumcastingalloys must contain7 ina++itiontostrengthening elements7 sufficient amounts of eutectic forming elements !usually silicon" in or+er toha6e a+e8uate flui+ity to fee+ the shrin1age that occurs in all but the simplest castings.,.1 Classi6cations of Cast Aluminum AlloysThey are classifie+ as un+er. 1##.#: Controlle+ unalloye+ compositions 2##.#: Aluminum alloys containing copper as the maEor alloying element 3##.#: Aluminum)silicon alloys are also containing magnesium an+@or copper 4##.#: 4inary aluminum)silicon alloys ##.#: Aluminum alloys containing magnesium as the maEor alloying element $##.#: Currently unuse+ #.#: Aluminumalloys containing :inc as the maEor alloying element7 usually alsocontaining a++itions of either copper7 magnesium7 chromium7 manganese7 or combinations ofthese elements (##.#: Aluminum alloys containing tin as the maEor alloying element *##.#: Currently unuse+=esignations in the form ###.1 an+ ###.2 inclu+e the composition of specific alloys in remelt ingotform suitable for foun+ry use. =esignations in the form ###., in all cases +efine composition limitsapplicable to castings. 0urther 6ariations in specifie+ compositions are +enote+ by prefi# letters use+primarily to +efine +ifferences in impurity limits. Accor+ingly7 one of the most common gra6ity castalloys73$7 has 6ariations A3$7 43$7 an+ C3$C each of these alloys has i+entical maEor alloycontents but has +ecreasing specification limits applicable to impurities7 especially iron content./n +esignations of the 1##.# type7 the secon+ an+ thir+ +igits in+icate minimum aluminum content!**.,,; or greater"C these +igits are the same as the t5o to the right of the +ecimal point in theminimumaluminumpercentage e#presse+ to the nearest ,.,1;. The fourth +igit in 1##.#Foundry EngineeringPage 12Aluminum alloys +esignations7 5hich is to the right of the +ecimal point7 in+icates pro+uct form: , +enotes castings!such as electric motor rotors"7 an+ 1 +enotes ingot./n2##.#through(##.#+esignations for aluminumalloys7 thesecon+an+thir++igits ha6enonumerical significance but only i+entify the 6arious alloys in the group. The +igit to the right of the+ecimal point in+icates pro+uct form: , +enotes castings7 1 +enotes stan+ar+ ingot7 an+ 2 +enotesingot ha6ing composition ranges narro5er than but 5ithin those of stan+ar+ ingot. Alloymo+ifications7 aspre6iouslymentione+7 arei+entifie+byacapitalletterprece+ingthenumerical+esignation.' Eect of alloyin! a++ition '.1 Aluminum(copper alloys 2$$.$:Aluminum-copperalloysthatcontain4to;Cu7 5iththeusualimpuritiesironan+siliconan+sometimes 5ith small amounts of magnesium7 are heat treatable an+ can reach 8uite high strengthsan+ +uctility7 especially if prepare+ from ingot containing less than ,.1; 0e. The aluminum)copperalloys aresingle)phasealloys. Inli1ethesiliconalloys7 thereis nohighlyflui+secon+phasea6ailable at the late stages of soli+ification. Ahen a6ailable7 a secon+ phase 5ill ai+ the re8uire+fee+ing of shrin1age areas an+ 5ill help compensate for soli+ification stresses./t is the alloy of aluminum an+ copper. An+ it is capable of +e6eloping highest strengths among allcastingalloys. 9oo+casting +esign an+foun+ry techni8uesmustbe use+togetfullmechanicalpropertiesan+consistent high8ualityparts. 9oo+hightemperaturestrength. Heat treatment isre8uire+ 5ith these alloys. 2o5er corrosion resistance an+ surface protection is re8uire+ in criticalapplications.'.1.1Commercial Al(Cu cast alloyA series of casting alloys such as (7 1,(7 31*7 an+ 3(,7 classe+ as aluminum)copper)silicon alloys7ha6e been +e6elope+ containing less than ; percent copper an+ from 3 to ( percent silicon.'.2 Aluminum(*ilicon alloy 7ith copper an+ ma!nesium 3$$.$/t isanalloyofaluminum)'iliconalloy5ithCopperan+@or%agnesium. Theyareinlo5cost7highest 6olume usage. There are three main types Al)'i)%g7 Al)'i)Cu or Al)'i)Cu)%g.Those 5ithcopper are heat treatable. 4oth copper an+ magnesium increase strength an+ har+ness in the as cast!f" temper an+ at ele6ate+ temperatures.Artificial aging is +one of these alloys.Aluminum)silicon alloys that +o not contain copper a++itions are use+ 5hen goo+ castability an+goo+ corrosion resistance are nee+e+.Foundry EngineeringPage 13Aluminum alloys /fhighstrengthan+har+nessarenee+e+7 magnesiuma++itionsma1ethesealloysheattreatable.Alloys 5ith silicon contents as lo5 as 2; ha6e been use+ for casting7 but silicon content usually isbet5eenan+ 13;. 'trength an+ +uctility of these alloys7 especially those 5ith higher silicon7 canbe substantially impro6e+ by mo+ification of the Al)'i eutectic.'.3 5inary aluminum(silicon alloys 4$$.$/t is an aluminum)silicon alloy. /t is base+ on the binary aluminum)silicon system an+ contains )12; silicon. /t has mo+erate strength an+ high +uctility impact resistance.'.3.1E$ample Al(*i cast alloyAluminum)silicon casting alloys ha6e e#cellent castability an+ resistance to corrosion. Alloy 13 !12percent silicon" an+alloy43!percent silicon" are use+for intricatecastings7 foo+)han+linge8uipment7 an+ marine fittings.'.4 Aluminum()a!nesium alloy 5$$.$/t is an aluminum magnesium alloy. /t has mo+erate to high strength an+ toughness. These alloysha6e high corrosion resistance especially to sea 5ater an+ marine atmospheres. They can be 5el+e+an+ goo+ machinability7 ano+i:e+. The relati6ely poor castability of Al)%g alloys an+ the ten+encyof the magnesium to o#i+i:e+ increase han+ling +ifficulties7 an+ therefore7 cost.These alloys are suitablefor 5el+e+assemblies an+are oftenuse+inarchitectural an+other+ecorati6e or buil+ing nee+s. 4est corrosion resistance re8uires lo5 impurity content !both soli+ an+gaseous"7 an+ thus alloys must be prepare+ from high)8uality metals an+ han+le+ 5ith great care inthe foun+ry.'.4.1Commercial Al()! cast alloyThe aluminum)magnesium casting alloys inclu+e alloy 214 !3.( percent magnesium"7 alloy 21( !(percent magnesium"7 an+ alloy 22, !1, percent magnesium". The first t5o are use+ for +airy an+foo+ han+ling e8uipment7 fittings for chemical an+ se5age use7 fittings for marine use7 an+ aircraftbra1e shoes. Alloy 22, is the only one in this group 5hich is age)har+en)able7 resulting in the highestmechanical properties of any of the aluminum casting alloys. The casting properties of alloys in thisgroup are poor7 an+ they re8uire careful foun+ry practice. '.5 Aluminum(-inc alloy '$$.$These alloys ha6e mo+erate to goo+ tensile properties in the as)cast con+ition. Castability of Al)-n)%galloysispoor7an+careful control ofsoli+ificationcon+itionsisre8uire+topro+ucesoun+7+efect free castings. Foundry EngineeringPage 14Aluminum alloys They are not generally recommen+e+ for ser6ice at ele6ate+ temperatures. The tensile properties ofthese alloys +e6elop at roomtemperatures +uring the first fe55ee1s after casting +ue toprecipitationhar+ening. This process continues thereafter at a progressi6elyslo5er rate. Heattreatments of the T$ an+ T& type may be applie+ to the &,&.,7 &&1.,7 an+ &&2., alloys'.5.1Commercial Al(-n alloyThe aluminum):inc casting alloy 1no5n as 4,E7 containing . percent :inc7 ,.$ percent magnesium7,.percent chromium7 an+,.2percent titanium7 pro6i+es highmechanical properties 5ithoutsolution treatment. This alloy also has fair casting characteristics7 goo+7 corrosion resistance7 an+6ery goo+ machinability. /t is use+ for aircraft fittings7 turret housings7 an+ ra+io e8uipment.'., Aluminum(Tin alloy /$$.$Aluminum)tinalloys that containabout $;'n!an+small amounts of copper an+nic1el forstrengthening" are use+ for cast bearings because of the e#cellent lubricity imparte+ by tin. These tin)containing alloys 5ere +e6elope+ for bearing applications !in 5hich loa+)carrying capacity7 fatiguestrength7 an+ resistance7 to corrosion by internal)combustion lubricating oil are important criteria".4earings of aluminum)tin alloys are superior o6erall to bearings ma+e using most other materials.4earingperformanceof Al)'nalloysisstronglyaffecte+bycastingmetho+. 0ineinter+en+ritic+istribution of tin7 5hich is necessary for optimum bearing properties7 re8uires small inter+en+riticspacing7 an+ small spacing is obtaine+ only 5ith casting metho+s in 5hich cooling is rapi+.0rom a foun+ry stan+point7 the aluminum)tin alloy system is uni8ue. /n the mol+7 the soli+ificationstarts at about $, JC !12,, J0"7 an+ the tin constituents of the alloy are li8ui+ until 22* JC !444 J0".Thise#tremelylargesoli+ificationrangepresentsuni8ueproblems. Kapi+soli+ificationratesarerecommen+e+ to a6oi+ e#cessi6e macrosegregation.'.,.1Commercial Al(Ti alloyAluminum)tincasting Alloys (,.,7 (1.,7 an+(2.,canbecast insan+orpermanent mol+s.Ho5e6er7 (,., !$.3'n)1Cu)1 Ni" an+ (2., !$.3'n)2 Cu)1.2 Ni),.(%g" usually are cast inpermanent mol+s. %aEor applications arefor connectingro+san+cran1casebearingsfor +ieselengines/ *ome common castin! alloys an+ their properties: A242:This alloyhasgoo+flui+ityan+sho5sresistancetohot crac1ingan+shrin1ageinthecastingprocess. /t has satisfactory 5el+ability by arc an+ resistance metho+s but bra:ing is notFoundry EngineeringPage 15Aluminum alloys recommen+e+. Typical applications inclu+e: motorcycle7 +iesel7 an+ aircraft engine pistons7 aircraftgenerator housings7 as 5ell as air coole+ cylin+er hea+s. A3:An aluminum alloy 5ith ,.,2; copper a++e+ for greatly impro6e+ strength o6er the more commonA3$ material. This alloy yiel+s highly consistent castings that are crac1 resistant7 easy to repair7 an+ha6e e#cellent tensile elongation properties. A3#:Aluminumalloysarecharacteri:e+by6erygoo+mechanical propertiesan+lo5porosity5ithaglobular microstructure 5hich is fine an+ uniform. The mechanical properties can be furtherimpro6e+throughheattreatmentssuchas Tan+ T$.Thesealloysareuse+forcastinggeneral)purpose +ie castings. The common alloys use+ are 3$)T$ for cast 5heels. A3#%.%:/s specifie+for +iecast parts that re8uiregoo+corrosionresistance'pecial alloys for specialapplications are a6ailable7 but their use usually entails significant cost premiums. . 3&3 ' 3&4:These alloys are a mo+ification of 3(,. 4oth pro6i+e better +ie filling7 but 5ith a mo+erate sacrificein mechanical properties7 such as toughness. A3(%:This alloy is hypereutectic aluminum)silicon alloy. The optimum structure of it must consist of fine7uniformly+istribute+primary'i crystals inaeutecticmatri#. This alloy+oes not re8uireheattreatment. The lo5 coefficient of thermal e#pansion7 high har+ness an+ goo+ 5ear resistance of thesealloys ma1e them suitable for internal combustion engines7 pistons an+ cylin+er bloc1s. 14:This alloy has a relati6ely poor flui+ity an+ a high +egree of +irectional soli+ification shrin1age.High pressure +ie casting is the primary metho+ of forming this alloy. This combination of materialproperties ma1es 14less castingfrien+ly. As aresult careful attentiontocastinggeometryisFoundry EngineeringPage 16Aluminum alloys essential. 4ecause of its poor flui+ity7 fine +etail an+ thin sections are +ifficult an+ ra+ii must be large4ecauseofshrin1age7 fee+ingthecastingre8uireslargerisersproper+esign. High+uctilityan+e#cellent corrosionresistance is themaina+6antageof this alloy. /t is commonlyfoun+boatpropellers 5here impact toughness is re8uire+.)eferen"es 3roperties an+ 'election: Nonferrous Alloys an+ 'pecial)3urpose %aterials 5as publishe+ in 1**, as Lolume 2of the1, E+ition %etals Han+boo1. HeatTreating5aspublishe+in1**1asLolume4oftheA'%Han+boo1. /ntro+uction to physical metallurgy 'i+ney H. A6ner. Heat treatment principal an+ techni8ues by C.3 'harma T.L KaEan an+ Asho1 'harma Foundry EngineeringPage 17