1 Aluminum Alloys:
Aluminum the most second plentiful metallic element on earth became an economic competitor in
engineering applications as recently as the end of the 19th century. It was to become a metal for its
time. For the most important industrial development would, by demanding material characteristic
consistent with the unique qualities of aluminum and its alloys. Greatly benefits growth in the
production and use of new metal.
2 Types of aluminum alloys
Aluminum alloys are alloys in which aluminum (Al) is the predominant metal. The typical alloying
elements are copper, magnesium, manganese, silicon and zinc. There are two principal
1. casting alloys
2. wrought alloys
Both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About
85% of aluminum is used for wrought products, for example rolled plate, foils and extrusions. Cast
aluminum alloys yield cost-effective products due to the low melting point, although they generally
have lower tensile strengths than wrought alloys. The most important cast aluminum alloy system
is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics.
Aluminum alloys are widely used in engineering structures and components where light weight or
corrosion resistance is required.
3 Cast aluminum Alloys:
The Aluminum Association (AA) has adopted a nomenclature similar to that of wrought
alloys. British Standard and DIN have different designations. In the AA system, the second two
digits reveal the minimum percentage of aluminum, e.g. 150.x corresponds to a minimum of 99.50%
aluminum. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot
respectively. The main alloying elements in the AA system are as follows.
1xx.x series are minimum 99% aluminum
2xx.x series copper
3xx.x series silicon, copper and/or magnesium
4xx.x series silicon
5xx.x series magnesium
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7xx.x series zinc
8xx.x series tin
9xx.x other elements
4 Heat treatment of cast aluminum alloys
When the term is applied to aluminum alloys, however, its use frequently is restricted to the specific
operations employed to increase strength and hardness of the precipitation hardenable wrought and
Heat treatable alloy
Non heat treatable alloy
4.1 Heat treatable alloy
Aluminum alloy of this type belongs to system with limited solubility in solid solution. These are
precipitated hardenable alloy. The main character of this type of alloy system is a temperature
dependent equilibrium solid solubility, which increase with increase in temperatue.in addition other
requirements are retaining single phase supersaturated solution by quenching and coherent state.
Examples of this group is
2xxx Al-Cu alloy and Al-Cu-Mg alloy.
6xxx series include Al-Zn, Al-Zn-Mg alloy
7xxx series include Al-Zn, Al-Zn-Mg-Cu type alloys
4.2 Non heat treatable cast alloys
These alloys do not respond to heat treatment because these alloys consist of homogeneous solid
solution with or without non-coherent precipitate and show low strength and high ductility.
Pure aluminum (1100), Al-Mn (3003)
5xxx Al-Mg alloys
6xxx Al-Si alloys
5 Effect of Alloying Elements:
5.1 Copper (Cu) 2xxx:
The aluminum-copper alloys typically contain between 2 to 10% copper, with smaller additions of
other elements. The copper provides substantial increases in strength and facilitates precipitation
hardening. The introduction of copper to aluminum can also reduce ductility aönd corrosion
resistance. The susceptibility to solidification cracking of aluminum-copper alloys is increased;
consequently, some of these alloys can be the most challenging aluminum alloys to weld. These
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alloys include some of the highest strength heat treatable aluminum alloys. The most common
applications for the 2xxx series alloys are aerospace, military vehicles and rocket fins.
The maximum solubility of copper in aluminum is 5.56% at 1018oF.
Figure 1: Al-Cu phase diagram
This is full phase diagram of aluminum and copper but useful portion is only up to 10% of copper.
From 2-5.56% of copper is mostly used for heat treatment purposes. The theta (θ) phase is an
intermediate alloy phase whose com-position corresponds closely to the compound CuAl2. These
alloys may contain smaller amounts of silicon, iron, magnesium, manganese, chromium, and zinc.
Table 1 phases present in Al-Cu phase diagram of heat treatable portion
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5.1.1 Commercial alloys of 2xxx series
The three most widely used wrought aluminum-copper alloys are 2014, 2017, and 2024.
188.8.131.52 Duralumin 2017 Al-Cu alloy
The oldest of all the heat treatable aluminum alloys is duralumin (2017) containing 4 percent copper.
This alloy is widely used for rivets in aircraft construction. Since this is a natural-aging alloy, after
solution treatment it is refrigerated to prevent aging. As a single phase, in the Solution treated
condition, it has good ductility so that the rivet head may be easily formed. Subsequent return of the
material to room temperature causes precipitation of the θ phase as small submicroscopic particles,
increasing the hardness and strength.
184.108.40.206 2014 Al-Cu alloy
Alloy 2014 has higher copper and manganese content than 2017 and is susceptible to artificial aging.
In the artificially aged temper, 2014 has a higher tensile strength, much higher yield strength, and
lower elongation than 2017. This alloy is used for heavy-duty forgings, aircraft fittings, and truck
220.127.116.11 2024 Al-Cu alloy
Alloy 2024, containing 4.5 percent copper and 1.5 percent magnesium, develops the highest
strengths of any naturally aged aluminum-copper type of alloy. The higher magnesium content,
compared with 2017, makes it more difficult to fabricate. A combination of strain hardening and
aging will develop the maximum yield strength attainable in high-strength alloy sheet. Typical uses
of 2024 alloy are aircraft structures, rivets, hardware, truck wheels and screw-machine products
5.2 Manganese (Mn) 3xxx
The addition of manganese to aluminum increases strength somewhat through solution strengthening
and improves strain hardening while not appreciably reducing ductility or corrosion resistance.
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Figure 2: Al-Mn phase diagram
These are moderate strength non-heat treatable materials that retain strength at elevated temperatures
and are seldom used for major structural applications.
The most common applications for the 3xxx series alloys are cooking utensils, radiators, air
conditioning condensers, evaporators, heat exchangers and associated piping systems. . The
maximum solubility of manganese in the solid solution is 1.82 at the eutectic temperature of 12160F.
Because of the limited solubility, manganese is not used as a major alloying element in any casting
alloys and is used in only a few wrought alloys.
5.2.1 Commercial alloys of 3xxx
One of the alloys in this group is the popular 3003 alloy, which has good formability, very good
resistance to corrosion, and good weldability. Typical applications are utensils, food and chemical
handling and storage equipment, gasoline and oil tank, pressure vessels and piping.
5.3 Silicon (Si) 4xxx
The addition of silicon to aluminum reduces melting temperature and improves fluidity. Silicon
alone in aluminum produces a non-heat treatable alloy; however, in combination with magnesium it
produces a precipitation hardening heat-treatable alloy. Consequently, there are both heat-treatable
and non-heat treatable alloys within the 4xxx series. Silicon additions to aluminum are commonly
used for the manufacturing of castings. The most common applications for the 4xxx series alloys are
filler wires for fusion welding and brazing of aluminum.
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Figure 3: Al-Si phase diagram
The aluminum-rich portion of the aluminum silicon alloy system is shown. The maximum solubility
of silicon in α solid solution is 1.65 percent at the eutectic temperature of 1071oF. Although the
solvus line shows lower solubility at lower temperatures, these alloys are generally not heat treatable.
5.4 Magnesium (Mg) 5xxx
The addition of magnesium to aluminum increases strength through solid solution strengthening and
improves their strain hardening ability. These alloys are the highest strength non heat treatable
aluminum alloys and are, therefore, used extensively for structural applications. The 5xxx series
alloys are produced mainly as sheet and plate and only occasionally as extrusions. The reason for
this is that these alloys strain harden quickly and, are, therefore difficult and expensive to extrude.
Although the solvus line, show considerable decrease in solubility with decrease in temperature of
magnesium in aluminum. Some common applications for the 5xxx series alloys are truck and train
bodies, buildings, armored vehicles, ship and boat building, chemical tankers, pressure vessels and
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Figure 4: Al-Mg phase diagram
5.4.1 Commercial Al-Mg alloys
The wrought alloys are characterized by good weldability, good corrosion resistance, and moderate
Alloy 5005 (0.8 percent magnesium) is used for architectural extrusions
alloy 5050 (1.2 percent magnesium) for tubing and automotive gas and oil lines
alloy 5083 (4.5 percent magnesium) for marine and welded structural applications; and alloy
(5.2 percent magnesium) for insect screens, cable sheathing, and rivets for use with
5.5 Magnesium and Silicon (Mg2Si) 6xxx
The addition of magnesium and silicon to aluminum produces the compound magnesium-silicide
(Mg2Si). The formation of this compound provides the 6xxx series their heat-treatability. The 6xxx
series alloys are easily and economically extruded and for this reason are most often found in an
extensive selection of extruded shapes. These alloys form an important complementary system with
the 5xxx series alloy.
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Figure 5: Al-Mg2Si phase diagram with aluminum rich portion
The 5xxx series alloy used in the form of plate and the 6xxx are often joined to the plate in some
extruded form. Some of the common applications for the 6xxx series alloys are handrails, drive
shafts, automotive frame sections, bicycle frames, tubular lawn furniture, scaffolding, stiffeners and
braces used on trucks, boats and many other structural fabrications.
5.5.1 Magnox Commercial alloys of 6xxx
The wrought alloys include 6053, 6061, and 6063 are mostly used.
18.104.22.168 6061 Al-Mg2Si
Construction of aircraft structures, such as wings and fuselages, more commonly
in homebuilt aircraft than commercial or military aircraft.
Construction, including small utility boats.
Automotive parts, such as wheel spacers.
Aluminum cans for the packaging of foodstuffs and beverages.
22.214.171.124 6053 Al-Mg2Si
Aluminum 6053 alloy is chiefly used in the manufacture of rod and wire for rivets. It is also
used in several cold heading applications, where it is used in the form of T-temper wire.
5.6 Zinc (Zn) 7xxx
The addition of zinc to aluminum (in conjunction with some other elements, primarily magnesium
and/or copper) produces heat-treatable aluminum alloys of the highest strength. The solubility of
zinc in aluminum is 31.6 percent at 527oF, decreasing to 5.6 percent at 257oF.
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Figure 6: Al-Zn phase diagram with aluminum rich portion
Commercial wrought alloys contain zinc, magnesium, and copper with smaller additions of
manganese and chromium. The zinc substantially increases strength and permits precipitation
hardening. Some of these alloys can be susceptible to stress corrosion cracking and for this reason
are not usually fusion welded. Other alloys within this series are often fusion welded with excellent
results. Some of the common applications of the 7xxx series alloys are aerospace, armored vehicles,
baseball bats and bicycle frames.
5.7 Others elements 8xxx
This series include elements which are rarely used in aluminum alloys. Some of these are impurity
5.7.1 Iron (Fe)
Iron is the most common impurity found in aluminum and is intentionally added to some pure (1xxx
series) alloys to provide a slight increase in strength.
5.7.2 Chromium (Cr)
Chromium is added to aluminum to control grain structure, to prevent grain growth in aluminum-magnesium
alloys, and to prevent recrystallization in aluminum-magnesium-silicon or aluminum-magnesium-
zinc alloys during heat treatment. Chromium will also reduce stress corrosion
susceptibility and improves toughness.
5.7.3 Nickel (Ni)
Nickel is added to aluminum-copper and to aluminum-silicon alloys to improve hardness and
strength at elevated temperatures and to reduce the coefficient of expansion.
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5.7.4 Titanium (Ti)
Titanium is added to aluminum primarily as a grain refiner. The grain refining effect of titanium is
enhanced if boron is present in the melt or if it is added as a master alloy containing boron largely
combined as TiB2. Titanium is a common addition to aluminum weld filler wire as it refines the
weld structure and helps to prevent weld cracking.
5.7.5 Zirconium (Zr)
Zirconium is added to aluminum to form a fine precipitate of intermetallic particles that inhibit
5.7.6 Lithium (Li)
The addition of lithium to aluminum can substantially increase strength and, Young’s modulus,
provide precipitation hardening and decreases density.
5.7.7 Lead (Pb) and Bismuth (Bi)
Lead and bismuth are added to aluminum to assist in chip formation and improve
machinability. These free machining alloys are often not weldable because the lead and bismuth
produce low melting constituents and can produce poor mechanical properties and/or high crack
sensitivity on solidification.
There are many aluminum alloys used in industry today - over 400 wrought alloys and over
200 casting allloys are currently registered with the Aluminum Association. Certainly one of
the most important considerations encountered during the welding of aluminum is the
identification of the aluminum base alloy type to be welded. If the base material type of the
component to be welded is not available through a reliable source, it can be difficult to select
a suitable welding procedure. There are some general guidelines as to the most probable type
of aluminum used in different applications, such as those mentioned above. However, it is
very important to be aware that incorrect assumptions as to the chemistry of an aluminum
alloy can result in very serious effects on the weld performance. It is strongly recommended
that positive identification of the type of aluminum is made and that welding procedures be
developed and tested in order to verify weld performance.
6 Cast Aluminum Alloys
Aluminum casting alloys are the most versatile of all common foundry alloys and generally have the
highest castability ratings.
Aluminum casting alloys are based on the same alloy systems as those of wrought aluminum alloys,
are strengthened by the same mechanisms (with the exception of strain hardening), and are
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similarly classified into non-heat-treatable and heat-treatable types. The major difference is that the
casting alloys used in the greatest volumes contains alloying additions of silicon far in excess of that
found (or used) in most wrought alloys. Aluminum casting alloys must contain, in addition to
strengthening elements, sufficient amounts of eutectic forming elements (usually silicon) in order to
have adequate fluidity to feed the shrinkage that occurs in all but the simplest castings.
6.1 Classifications of Cast Aluminum Alloys
They are classified as under.
1xx.x: Controlled unalloyed compositions
2xx.x: Aluminum alloys containing copper as the major alloying element
3xx.x: Aluminum-silicon alloys are also containing magnesium and/or copper
4xx.x: Binary aluminum-silicon alloys
5xx.x: Aluminum alloys containing magnesium as the major alloying element
6xx.x: Currently unused
7xx.x: Aluminum alloys containing zinc as the major alloying element, usually also
containing additions of either copper, magnesium, chromium, manganese, or combinations of
8xx.x: Aluminum alloys containing tin as the major alloying element
9xx.x: Currently unused
Designations in the form xxx.1 and xxx.2 include the composition of specific alloys in remelt ingot
form suitable for foundry use. Designations in the form xxx.0 in all cases define composition limits
applicable to castings. Further variations in specified compositions are denoted by prefix letters used
primarily to define differences in impurity limits. Accordingly, one of the most common gravity cast
alloys, 356, has variations A356, B356, and C356; each of these alloys has identical major alloy
contents but has decreasing specification limits applicable to impurities, especially iron content.
In designations of the 1xx.x type, the second and third digits indicate minimum aluminum content
(99.00% or greater); these digits are the same as the two to the right of the decimal point in the
minimum aluminum percentage expressed to the nearest 0.01%. The fourth digit in 1xx.x
designations, which is to the right of the decimal point, indicates product form: 0 denotes castings
(such as electric motor rotors), and 1 denotes ingot.
In 2xx.x through 8xx.x designations for aluminum alloys, the second and third digits have no
numerical significance but only identify the various alloys in the group. The digit to the right of the
decimal point indicates product form: 0 denotes castings, 1 denotes standard ingot, and 2 denotes
ingot having composition ranges narrower than but within those of standard ingot. Alloy
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modifications, as previously mentioned, are identified by a capital letter preceding the numerical
7 Effect of alloying addition
7.1 Aluminum-copper alloys 2xx.x:
Aluminum-copper alloys that contain 4 to 5% Cu, with the usual impurities iron and silicon and
sometimes with small amounts of magnesium, are heat treatable and can reach quite high strengths
and ductility, especially if prepared from ingot containing less than 0.15% Fe. The aluminum-copper
alloys are single-phase alloys. Unlike the silicon alloys, there is no highly fluid second phase
available at the late stages of solidification. When available, a second phase will aid the required
feeding of shrinkage areas and will help compensate for solidification stresses.
It is the alloy of aluminum and copper. And it is capable of developing highest strengths among all
casting alloys. Good casting design and foundry techniques must be used to get full mechanical
properties and consistent high quality parts. Good high temperature strength. Heat treatment is
required with these alloys. Lower corrosion resistance and surface protection is required in critical
7.1.1 Commercial Al-Cu cast alloy
A series of casting alloys such as 85, 108, 319, and 380, classed as aluminum-copper-silicon alloys,
have been developed containing less than 5% percent copper and from 3 to 8 percent silicon.
7.2 Aluminum-Silicon alloy with copper and magnesium 3xx.x
It is an alloy of aluminum-Silicon alloy with Copper and/or Magnesium. They are in low cost,
highest volume usage. There are three main types Al-Si-Mg, Al-Si-Cu or Al-Si-Cu-Mg. Those with
copper are heat treatable. Both copper and magnesium increase strength and hardness in the as cast
(f) temper and at elevated temperatures. Artificial aging is done of these alloys.
Aluminum-silicon alloys that do not contain copper additions are used when good castability and
good corrosion resistance are needed.
If high strength and hardness are needed, magnesium additions make these alloys heat treatable.
Alloys with silicon contents as low as 2% have been used for casting, but silicon content usually is
between 5 and 13%. Strength and ductility of these alloys, especially those with higher silicon, can
be substantially improved by modification of the Al-Si eutectic.
7.3 Binary aluminum-silicon alloys 4xx.x
It is an aluminum-silicon alloy. It is based on the binary aluminum-silicon system and contains 5-
12% silicon. It has moderate strength and high ductility impact resistance.
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7.3.1 Example Al-Si cast alloy
Aluminum-silicon casting alloys have excellent castability and resistance to corrosion. Alloy 13 (12
percent silicon) and alloy 43 (5 percent silicon) are used for intricate castings, food-handling
equipment, and marine fittings.
7.4 Aluminum-Magnesium alloy 5xx.x
It is an aluminum magnesium alloy. It has moderate to high strength and toughness. These alloys
have high corrosion resistance especially to sea water and marine atmospheres. They can be welded
and good machinability, anodized. The relatively poor castability of Al-Mg alloys and the tendency
of the magnesium to oxidized increase handling difficulties, and therefore, cost.
These alloys are suitable for welded assemblies and are often used in architectural and other
decorative or building needs. Best corrosion resistance requires low impurity content (both solid and
gaseous), and thus alloys must be prepared from high-quality metals and handled with great care in
7.4.1 Commercial Al-Mg cast alloy
The aluminum-magnesium casting alloys include alloy 214 (3.8 percent magnesium), alloy 218 (8
percent magnesium), and alloy 220 (10 percent magnesium). The first two are used for dairy and
food handling equipment, fittings for chemical and sewage use, fittings for marine use, and aircraft
brake shoes. Alloy 220 is the only one in this group which is age-harden-able, resulting in the highest
mechanical properties of any of the aluminum casting alloys. The casting properties of alloys in this
group are poor, and they require careful foundry practice.
7.5 Aluminum-Zinc alloy 7xx.x
These alloys have moderate to good tensile properties in the as-cast condition. Castability of Al-Zn-
Mg alloys is poor, and careful control of solidification conditions is required to produce sound,
defect free castings.
They are not generally recommended for service at elevated temperatures. The tensile properties of
these alloys develop at room temperatures during the first few weeks after casting due to
precipitation hardening. This process continues thereafter at a progressively slower rate. Heat
treatments of the T6 and T7 type may be applied to the 707.0, 771.0, and 772.0 alloys
7.5.1 Commercial Al-Zn alloy
The aluminum-zinc casting alloy known as 40E, containing 5.5 percent zinc, 0.6 percent magnesium,
0.5 percent chromium, and 0.2 percent titanium, provides high mechanical properties without
solution treatment. This alloy also has fair casting characteristics, good, corrosion resistance, and
very good machinability. It is used for aircraft fittings, turret housings, and radio equipment.
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7.6 Aluminum-Tin alloy 8xx.x
Aluminum-tin alloys that contain about 6% Sn (and small amounts of copper and nickel for
strengthening) are used for cast bearings because of the excellent lubricity imparted by tin. These tin-containing
alloys were developed for bearing applications (in which load-carrying capacity, fatigue
strength, and resistance, to corrosion by internal-combustion lubricating oil are important criteria).
Bearings of aluminum-tin alloys are superior overall to bearings made using most other materials.
Bearing performance of Al-Sn alloys is strongly affected by casting method. Fine interdendritic
distribution of tin, which is necessary for optimum bearing properties, requires small interdendritic
spacing, and small spacing is obtained only with casting methods in which cooling is rapid.
From a foundry standpoint, the aluminum-tin alloy system is unique. In the mold, the solidification
starts at about 650 °C (1200 °F), and the tin constituents of the alloy are liquid until 229 °C (444 °F).
This extremely large solidification range presents unique problems. Rapid solidification rates are
recommended to avoid excessive macrosegregation.
7.6.1 Commercial Al-Ti alloy
Aluminum-tin casting Alloys 850.0, 851.0, and 852.0 can be cast in sand or permanent molds.
However, 850.0 (6.3Sn-1Cu-1 Ni) and 852.0 (6.3Sn-2 Cu-1.2 Ni-0.8Mg) usually are cast in
permanent molds. Major applications are for connecting rods and crankcase bearings for diesel
8 Some common casting alloys and their properties:
This alloy has good fluidity and shows resistance to hot cracking and shrinkage in the casting
process. It has satisfactory weldability by arc and resistance methods but brazing is not
recommended. Typical applications include: motorcycle, diesel, and aircraft engine pistons, aircraft
generator housings, as well as air cooled cylinder heads.
An aluminum alloy with 0.02% copper added for greatly improved strength over the more common
A356 material. This alloy yields highly consistent castings that are crack resistant, easy to repair, and
have excellent tensile elongation properties.
Aluminum alloys are characterized by very good mechanical properties and low porosity with a
globular microstructure which is fine and uniform. The mechanical properties can be further
improved through heat treatments such as T5 and T6. These alloys are used for casting general-purpose
die castings. The common alloys used are 356-T6 for cast wheels.
Is specified for die cast parts that require good corrosion resistance Special alloys for special
applications are available, but their use usually entails significant cost premiums. .
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383 & 384:
These alloys are a modification of 380. Both provide better die filling, but with a moderate sacrifice
in mechanical properties, such as toughness.
This alloy is hypereutectic aluminum-silicon alloy. The optimum structure of it must consist of fine,
uniformly distributed primary Si crystals in a eutectic matrix. This alloy does not require heat
treatment. The low coefficient of thermal expansion, high hardness and good wear resistance of these
alloys make them suitable for internal combustion engines, pistons and cylinder blocks.
This alloy has a relatively poor fluidity and a high degree of directional solidification shrinkage.
High pressure die casting is the primary method of forming this alloy. This combination of material
properties makes 514 less casting friendly. As a result careful attention to casting geometry is
essential. Because of its poor fluidity, fine detail and thin sections are difficult and radii must be
large Because of shrinkage, feeding the casting requires large risers proper design. High ductility and
excellent corrosion resistance is the main advantage of this alloy. It is commonly found boat
propellers where impact toughness is required.
Properties and Selection: Nonferrous Alloys and Special-Purpose Materials was published in 1990 as Volume 2
of the10 Edition Metals Handbook.
Heat Treating was published in 1991 as Volume 4 of the ASM Handbook.
Introduction to physical metallurgy Sidney H. Avner.
Heat treatment principal and techniques by C.P Sharma T.V Rajan and Ashok Sharma
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