Aluminum –Properties
Low relative density Highly Pure Al(>99.5%) soft, does not show a ductile-to-
Good Corrosion resistance weak ; suitable for lining of brittle transition at low
Good Electrical Conductivity vessels in food and chemical temperatures.
Good Thermal Conductivity industries It is nontoxic
Great affinity for O2 Aluminum: lighter, excellent can be recycled with only
FCC, ductile, hot and cold sp. Strength. about 5% of Al2O3 (energy)-
work, no annealing twins It can be formed easily, -Al
It has high thermal and
electrical conductivity,
Application
About 25%--transportation industry, another 25%--beverage cans and other packaging, about 15%--
construction, 15% -- electrical applications, and 20%-- in other applications.
Aluminum Alloy
Aluminum alloys -- wrought and casting alloys.
Wrought alloys, which are shaped by plastic deformation
Casting alloys, processed by casting
each major group: two subgroups: heat treatable and non heat-treatable alloys.
Designation of Aluminum Alloys
Alloy Group Major Alloying Elements
1xxx Aluminum (99.0% min. and greater)
2xxx Copper
3xxx Manganese
4xxx Silicon
5xxx Magnesium
6xxx Mg + Si
7xxx Zinc
8xxx Other elements
9xxx Unused series
The first number specifies the principle alloying elements, and the remaining numbers refer to the specific
composition of the alloy.
Alloy Composition Tensile Yield Strength Applications
Strength (psi) (psi)
Non Heat-Treatable
Wrought Alloys
1100-O >99% Al 13,000 5,000 Electrical components, foil, food processing
1100-H18 24,000 22,000
3004-O 1.2% Mn-1.0% 26,000 10,000 Beverage can bodies, architectural uses
Mg
3004-H18 41,000 36,000
4043-O 5.2% Si 21,000 10,000 Filler metal for welding, beverage can tops,
and marine components
4043-H18 41,000 39,000
5182-O 4.5% Mg 42,000 19,000 Marine components
5182-H19 61,000 57,000
Heat-Treatable Wrought
Alloys
2024-T4 4.4% Cu 68,000 47,000 Truck wheels, aircraft skins, pistons, canoes
2090-T6 2.4% Li-2.7% 80,000 75,000 Railroad cars, and aircraft frames
Cu
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4032-T6 12% Si-1% Mg 55,000 46,000
6061-T6 1% Mg-0.6% Si 45,000 40,000
7075-T6 5.6% Zn-2.5% 83,000 73,000
Mg
Casting Alloys
201-T6 4.5% Cu 70,000 63,000 Transmission housings
319-F 6% Si-3.5% Cu 27,000 18,000 General purpose castings, aircraft fittings,
motor housings
356-T6 7% Si-0.3% Mg 33,000 24,000 Automotive engines, food-handling
equipment
380-F 8.5% Si-3.5% 46,000 23,000
Cu
390-F 17% Si-4.5% Cu 41,000 35,000
443-F (sand cast) 5.2% Si 19,000 8,000 Marine fittings
443-F (permanent mold) 23,000 9,000
443-F (die cast) 33,000 16,000
Wrought Alloys
The 1xxx, 3xxx, 5xxx, and most of the 4xxx wrought alloys are not age hardenable. The 1xxx and 3xxx alloys
are singlephase alloys except for the presence of small amounts of inclusions or intermetallic compounds (Figure
14-1).
Their properties are controlled by strain hardening, solidsolution strengthening, and grain-size control. Because
the solubilities of the alloying elements in aluminum are small at room temperature, the degree of solid-solution
strengthening is limited.
The 5xxx alloys contain two phases at room temperature—, a solid solution of magnesium in aluminum, and
Mg2Al3, a hard, brittle intermetallic compound (Figure 14-2).
The aluminum-magnesium alloys are strengthened by a fine dispersion of Mg2Al3, as well as by strain
hardening, solid-solution strengthening, and grain-size control. Because Mg2Al3 is not coherent, age hardening
treatments are not possible.
The 4xxx series alloys also contain two phases, and nearly pure silicon, (Al-Si Phase Diagram)
Alloys that contain both silicon and magnesium can be age hardened by permitting Mg2Si to precipitate.
Al-Si Alloys
Heat-treatable Aluminum Alloys
Wrought Alloys: Al/Cu/Mg/Si alloys • Can be precipitated hardened
Al/Zn/Mg/Cu Alloys • Al-4%Cu Duralumin
Al/Mg/Si Alloys • Maximum solubility 5.7% at 548 C
• Decreases to 0.2% at RT
Al-4%Cu -- α and θ(CuAl2) -- hard brittle intermetallic compound. Slow cooling -- Course particle ppt at the
grain boundary -- resulting in poor mechanical properties
With soln tr. and aging can give much improved mechanical properties.
Steps 1: heating
Steps 2: quenching
Steps 3. aging
• Duralumin (Al/4%Cu/0.5%Mg/0.5%Mn/0.5%Si) -- soln 490C+quenching + RT aging (4days) --
aircrafts (forgings, extrusions, tubes and rivets
• Al/Zn/Mg/Cu : highest strength (HT Al alloys): forgings and extrusions (aircraft) -- not easily worked
and subjected to SCC.
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• Al/Mg/Si -- commonly used Al alloys. MgSi2 intermetallics formed. A binary phase of Al and MgSi2.
Good CR, Fairly good strength. Structures, containers and vehicles.
2. Casting Alloys- HT is similar that for wrought alloys. (soln -- longer) Pr. Die cast not Age hardened
because of blistering
Al -- Mg, Cu, Si, (Ni). Common alloy (4%Cu, 1.5%Mg, 2%Ni). Ni ↑ OAT↑ Alloy can be used at elevated
temp. fairly good CR.
1. Soln Tr (520C, 6 hrs) 2. quenching, 3. Aging (100C, 2hrs). Piston, cylinder block, head for IC engines.
Aluminum alloys that are not age-hardenable, also known as non-heat-treatable alloys, primarily belong to the 1xxx,
3xxx, 4xxx, and 5xxx series. These alloys rely on cold working to improve their strength rather than heat treatment.
Here's a brief overview:
1. 1xxx Series (Pure Aluminum): Contains 99% or higher aluminum content. They are not heat-treatable and
have excellent corrosion resistance.
2. 3xxx Series (Aluminum-Manganese Alloys): Typically contains 1-2% manganese. These alloys are also non-
heat-treatable and are known for good corrosion resistance and moderate strength.
3. 4xxx Series (Aluminum-Silicon Alloys): Contains silicon as the main alloying element. They are primarily
used in welding filler materials and are non-heat-treatable.
4. 5xxx Series (Aluminum-Magnesium Alloys): Contains magnesium as the principal alloying element, which
provides good corrosion resistance and moderate strength. These alloys are non-heat-treatable but are often used in
marine applications due to their excellent resistance to seawater corrosion.
In contrast, alloys from the 2xxx, 6xxx, and 7xxx series are typically agehardenable and respond well to heat
treatment.
Non-age-hardenable aluminum alloys, like those in the 1xxx, 3xxx, 4xxx, and 5xxx series, are not capable of age
hardening due to the absence of certain alloying elements that would allow them to undergo precipitation hardening.
The age-hardening process relies on the formation of fine, uniformly distributed precipitates within the alloy's matrix,
which strengthens the material.
Lack of Suitable Alloying Elements:
- Age hardening requires specific alloying elements such as copper (Cu), magnesium (Mg), silicon (Si), or zinc
(Zn), which can form intermetallic compounds upon aging. These compounds precipitate out of the solid solution
during the heat treatment process and obstruct dislocation movement, thereby strengthening the material.
- Non-heat-treatable alloys do not contain the necessary concentrations of these elements in combinations that
would allow for significant precipitation hardening.
Solid Solution Strengthening: - In non-heat-treatable alloys, elements like manganese (Mn), magnesium (Mg), or
silicon (Si) are added in amounts that lead to solid solution strengthening rather than precipitation hardening. These
elements dissolve in the aluminum matrix and strengthen the alloy through mechanisms such as solid solution
strengthening or grain boundary strengthening, which does not rely on age hardening.
Stability of Phases:
In non-heat-treatable alloys, the phases present are stable at room temperature and do not undergo significant changes
during the aging process. For example, in the 3xxx series, manganese is present as a stable phase and does not
precipitate out to form fine particles during heat treatment.
Primary Strengthening Mechanism:
For non-heat-treatable alloys, the primary means of strengthening is through work hardening or strain hardening,
where the alloy's strength is increased by plastic deformation processes like rolling or drawing. This contrasts with
age-hardenable alloys, where the strength is enhanced through controlled heat treatment and aging.
In summary, non-age-hardenable aluminum alloys lack the right composition of alloying elements and mechanisms
necessary for precipitation hardening, relying instead on other methods like work hardening for strength enhancement.
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