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