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Aluminum
Aluminum is widely used in passenger rail vehicle design
and construction in both structural and decorative applications.
Common aluminum alloys and designations are provided
in the table at the end of this section.
The Aluminum Association also has a comprehensive set of
specification for the general appearance of aluminum finishing.
The finish designations are widely recognized and offer
more alternatives to the commonly used MIL standards. The
following specifications are an excerpt from the Aluminum
Association, Designation System for Aluminum Finishes, 45.
The Aluminum Association may be contacted at (202)-862-5100,
or 818 Connecticut Ave. N.W., Washington D.C. 20006.
For aluminum anodized finish specifications for “cosmetic”
appearance surfaces, the following two examples of the standards
would be used to describe typical finishes:
Cosmetic, clear anodizing - “AA-M31C23A31,
0.0004" THK, Clear”
Cosmetic, black anodizing - “AA-M31C23A32,
0.0004" THK, Black”
The following is an explanation of what each component
of the specification means:
AA - Aluminum Association Designation
M31 - Mechanical Finish, Fine Satin direction texture
C23 - Chemical Finish, Etched, Coarse Matte
A31 - Coating, Protective and Decorative, Clear
A32 - Coating, Protective and Decorative, Integral Color,
Black (the color must be specified)
0.0004" THK - this is the specified thickness for the
anodic coating. Up to 0.0007" THK thickness may be
specified for exterior applications.
The complete specification must be referenced to provide
this finish. The AA standard includes definitions for a
wide variety of finish combinations.
For aluminum anodized finish specifications for “utility”
(non-cosmetic) surfaces, the following standards are more
appropriate:
For interior utility coatings use - MIL-A-8625F, Type II,
Class 1 (clear)
For exterior utility (hard anodize) coatings use - MIL-A-8625F,
Type III, Class 1 (clear)
Other “classes” are available in this designation
if color is desired.
The following standards provide general guidelines for
aluminum fabrication.
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| Standard: |
AA - Aluminum Association Standards for Aluminum Mill Products
| | Purpose: |
Aluminum Association standards provide tolerance, alloys, and guidelines for the manufacture of aluminum extrusions, and aluminum Mill products for manufacture in the USA.
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| Criteria: |
Specify compliance with standard
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| Usage: |
.... shall be in compliance with the Aluminum Association Standards for aluminum mill products
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| Standard: |
APTA SS-C&S-015-98 Standard for Aluminum and Aluminum Alloys for Passenger Equipment Car Body Construction
| | Purpose: |
This Standard provides a guide for the selection of appropriate aluminum alloys for rail
passenger equipment used in fabrication of passenger railroad equipment. In addition to basic information on the grades of aluminum alloys and their designations, this standard also includes precautions for selecting, welding, and handling the aluminum alloys.
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| Criteria: |
Specify compliance with standard
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| Usage: |
Shall comply with applicable requirements of APTA SS-C&S-015-98
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| Standard: |
ASTM B108 - Aluminum-Alloy Permanent Mold Castings
| | Purpose: |
This specification covers aluminum alloys and composition, heat treatment, and strength requirements for aluminum used in permanent mold castings.
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| Criteria: |
Specify standard name, alloy, and temper required
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| Usage: |
ASTM B108, 356.0, T6
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| Standard: |
ASTM B247 - Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings
| | Purpose: |
This specification covers aluminum alloys and composition, heat treatment, and strength requirements for die forgings, hand forgings, and rolled ring forgings.
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| Criteria: |
Specify standard name, alloy, and temper required
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| Usage: |
ASTM B247, 6061, T6
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| Standard: |
ASTM B26 - Standard Specification for Aluminum-Alloy Sand Castings
| | Purpose: |
This specification covers aluminum alloys and composition, heat treatment, and strength requirements for die forgings, hand forgings, and rolled ring forgings.
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| Criteria: |
Specify standard name, alloy, and temper required
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| Usage: |
ASTM B26, 356.0, T6
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| Standard: |
ASTM B85 - Standard Specification for Aluminum-Alloy Die Castings
| | Purpose: |
This specification covers aluminum alloys and composition requirements for die forgings, hand forgings, and rolled ring forgings. Mechanical properties are not covered in this standard.
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| Criteria: |
Specify standard name, alloy
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| Usage: |
ASTM B85, 380
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| Wrought & Cast |
Common Usage |
Wrought Alloys |
Work Hardened |
Heat Treated |
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Pure Aluminum is a soft, ductile, corrosion resistant material
that is widely used in a variety of applications. Aluminum
in it's natural state is relatively soft and generally not
suitable for structural applications, however, alloying
pure aluminum with other elements will provide the higher
strengths needed for other applications. Aluminum also has
a high electrical conductivity, and it is widely used for
electrical conductor cables and electrical shielding foil.
General Properties
| Property |
Value |
| Density (lb/ft3
| g/cm3 | Specific Gravity) |
164 | 2.7 | 2.7 |
| Modulus of Elasticity (GPa)
|
68.3 |
| Poissons Ratio |
0.34 |
| Melting Point |
1220°F | 660°C |
| Mean Specific Heat (0-100°C)
(cal/g.°C) |
0.214 |
| Coefficient of Heat Transmission
(BTU/sec) |
0.00203 |
| Co-Efficient of Linear
Expansion (in/in/°Fx10-6) (cm/cm/°Cx10-6)
|
12 | 22 |
| Electrical Conductivity
(Compared to Cu) |
62% |
Wrought and Cast Aluminum Alloy Types
The main alloying elements are copper, zinc, magnesium,
silicon, manganese and lithium. Small additions of chromium,
titanium, zirconium, lead, bismuth and nickel are also made
and iron is invariably present in small quantities. There
are over 300 wrought alloys with 50 in common use. They
are normally identified by a four figure system which originated
in the USA and is now universally accepted. Table 2 describes
the system for wrought alloys. Cast alloys have similar
designations and use a five digit system (table 2). Table
3 lists the designations, characteristics, common uses and
forms of some widely used alloys.
Alloy Designation Group Types
Wrought |
Cast |
Major Alloying
Element |
| 1XXX |
1XXX0 |
None (99%+ Aluminum) |
| 2XXX |
2XXX0 |
Copper |
| 3XXX |
|
Manganese |
| 4XXX |
4XXX0 |
Silicon |
| 5XXX |
5XXX0 |
Magnesium |
| 6XXX |
6XXX0 |
Magnesium + Silicon |
| 7XXX |
7XXX0 |
Zinc |
| 8XXX |
|
Lithium |
| |
9XXX0 |
Unused |
Common Alloy Types and Applications
| Alloy |
Characteristics |
Common
Uses |
Form |
| 1050/1200 |
Good formability, weld ability and
corrosion resistance |
Food and chemical industry. |
Plate, Sheet |
| 2014A |
Heat treatable.
High strength.
Non-weldable.
Poor corrosion resistance. |
Airframes. |
Extrusion, Plate |
| 3103/3003 |
Non-heat treatable.
Medium strength work hardening alloy.
Good weld ability, formability and corrosion resistance.
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Vehicle paneling, structures exposed
to marine atmospheres, mine cages. |
Extrusion, Plate, Sheet |
| 5251/5052 |
Non-heat treatable.
Medium strength work hardening alloy.
Good weld ability, formability and corrosion resistance.
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Vehicle paneling, structures exposed
to marine atmospheres, mine cages. |
Plate, Sheet |
| 5454 |
Non-heat treatable.
Used at temperatures from 65-200°C.
Good weld ability and corrosion resistance. |
Pressure vessels and road tankers.
Transport of ammonium nitrate, petroleum.
Chemical plants. |
Plate, Sheet |
| 5083/5182 |
Non-heat treatable.
Good weld ability and corrosion resistance.
Very resistant to sea water, industrial atmospheres.
A superior alloy for cryogenic use (in annealed condition)
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Pressure vessels and road transport
applications below 65°C.
Ship building structure in general. |
Extrusion, Plate, Sheet |
| 6063 |
Heat treatable.
Medium strength alloy.
Good weld ability and corrosion resistance.
Used for intricate profiles. |
Architectural extrusions (internal
and external), window frames, irrigation pipes. |
Extrusion |
| 6061/6082 |
Heat treatable.
Medium strength alloy.
Good weld ability and corrosion resistance. |
Stressed structural members, bridges,
cranes, roof trusses, beer barrels. |
Extrusion, Plate, Sheet |
| 6005A |
Heat treatable.
Properties very similar to 6082.
Preferable as air quenchable, therefore has less distortion
problems.
Not notch sensitive. |
Thin walled wide extrusions. |
Extrusion |
| 7020 |
Heat treatable.
Age hardens naturally therefore will recover properties
in heat affected zone after welding.
Susceptible to stress corrosion.
Good ballistic deterrent properties. |
Armored vehicles, military bridges,
motor cycle and bicycle frames. |
Extrusion, Plate |
| 7075 |
Heat treatable.
Very high strength.
Non-weldable.
Poor corrosion resistance. |
Airframes. |
Extrusion, Plate |
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Hardening Methods for Aluminum
Aluminum alloys may be separated into two hardenability categories; Those which
derive their properties from work hardening, and those which
depend upon solution heat treatment and age hardening.
Work Hardened Aluminum Alloys
The 1000, 3000 and 5000 series alloys are work hardenable
alloys that have their strength properties modified by cold
work, usually performed as a part of the fabrication process
such as by cold rolling. The properties of these alloys
vary by the degree of cold work and annealing or stabilizing
thermal treatment (if used), that follows the cold work.
The work hardening designations use a letter, O, F or H
followed by one or more numbers. The designations that start
with "H" are followed by two digits; the first digit designates
the process combination used to obtain the hardening, the
second digit is used to indicate the degree of the hardening
process.
The following tables identify the work hardening designations
and the levels typically used.
Work Hardening Designation Levels
| Term |
Description |
| O |
Fully soft annealed condition |
| F |
As fabricated material that receives
no subsequent treatment |
| H1x |
Strain-hardened only, without
supplementary thermal treatment |
| H2x |
Strain-hardened and partially
annealed. These designations apply to products which
are strain-hardened more than the desired final level,
and then reduced in strength to the desired level
by partial annealing. For alloys that age-soften at
room temperature, the H2x tempers have the same minimum
ultimate tensile strength as the corresponding H3x
tempers. For other alloys, the H2x tempers have the
same minimum ultimate tensile strength as the corresponding
H1x tempers and slightly higher elongation |
| H3x |
Strain-hardened and stabilized.
These designations apply to products which are strain-hardened
and whose mechanical properties are stabilized. either
by a low temperature thermal treatment or as a result
of heat introduced during fabrication. Stabilization
usually improves ductility. This designation is applicable
only to those alloys which, unless stabilized, gradually
age soften at room temperature |
| H4x |
H4x Strain-hardened and powder
coated or painted. These designations apply to products
which are strain-hardened and which may be subjected
to some partial annealing during the thermal curing
which follows the painting or powder coating operation.
The second number after H indicates the final degree
of strain-hardening, number 8 being the hardest normally
indicated.
The third digit after H, when used, indicates a variation
of a two digit temper. It is used when the degree
of control of temper or the mechanical properties
or both differ from, but are close to, that (or those)
for the two digit H temper designation to which it
is added, or when some other characteristic is significantly
affected. |
Work Hardening Designations
| New Symbol |
Description |
Old BS Symbol |
| O |
Annealed, soft |
O |
| F |
As fabricated |
M |
| H12 |
Strain-hardened, quarter hard |
H2 |
| H14 |
Strain-hardened, half hard |
H4 |
| H16 |
Strain-hardened, three quarter hard
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H6 |
| H18 |
Strain-hardened, fully hard |
H8 |
| H22 |
Strain-hardened, partially annealed
quarter hard |
H2 |
| H24 |
Strain-hardened, partially annealed
half hard |
H4 |
| H26 |
Strain-hardened, partially annealed
three quarter hard |
H6 |
| H28 |
Strain-hardened, partially annealed
fully hard |
H8 |
| H32 |
Strain-hardened and stabilized., quarter
hard |
H2 |
| H34 |
Strain-hardened and stabilized., half
hard |
H4 |
| H36 |
Strain-hardened and stabilized., three
quarter hard |
H6 |
| H38 |
Strain-hardened and stabilized., fully
hard |
H8 |
The degree of cold work and variation of annealing
provide a wide range of mechanical properties for these
aluminum alloys.
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Solution Heat Treated and Age Hardened
Aluminum Alloys The 2000, 4000, 6000,
7000 and 8000 series alloys are heat treatable by a variety
and/or combination of treatments.
Thermally treated aluminum alloys are indicated by a "T"
designation following the alloy number (e.g. 6061 T6). These
heat treatments may be supplementaly treated with strain
hardening, As with work hardening, each temper designation
"T" is followed by a second digit to indicate
the heat treatment process used. Additional digits may also
be used to designate additional treatments applied after
the initial heat treatment. Each of the specific numbers
defines a separate process as identified in the following
table.
Heat treatment designations for Aluminum
and Aluminum alloys
| Term |
Description |
| T1 |
Cooled from an elevated
temperature shaping process and naturally aged to
a substantially stable condition.
This designation applies to products which are not
cold worked after cooling from an elevated temperature
shaping process, or in which the effect of cold work
in flattening or straightening has no effect on mechanical
properties |
| T2 |
Cooled from an elevated
temperature shaping process, cold worked and naturally
aged to a substantially stable condition.
This designation applies to products which are cold
worked to improve strength after cooling from an elevated
temperature shaping process, or in which the effect
of cold work in flattening or straightening does have
an effect on mechanical properties. |
| T3 |
Solution heat-treated,
cold worked and naturally aged to a substantially
stable condition.
This designation applies to products which are cold
worked to improve strength after solution heat-treatment,
or in which the effect of cold work in flattening
or straightening does have an effect on mechanical
properties. |
| T4 |
Solution heat-treated and
naturally aged to a substantially stable condition.
This designation applies to products which are not
cold worked after solution heat-treatment, or in which
the effect of cold work in flattening or straightening
does not effect mechanical properties. |
| T5 |
Cooled from an elevated
temperature shaping process and then artificially
aged.
This designation applies to products which are not
cold worked after cooling from an elevated temperature
shaping process, or in which the effect of cold work
in flattening or straightening does not effect mechanical
properties. |
| T6 |
Solution heat-treated
and then artificially aged.
This designation applies to products which are not
cold worked after solution heat-treatment, or in
which the effect of cold work in flattening or straightening
does not effect mechanical properties. |
| T7 |
Solution heat-treated and
overaged/stabilized.
This designation applies to products which are artificially
aged after solution heat-treatment to carry them beyond
a point of maximum strength to provide control of
some significant characteristic other than mechanical
properties. |
| T_51 |
Stress relieved by stretching (0.5
to 3% permanent set depending upon configuration) |
| T_510 |
Products that receive no further straightening
after stretching |
| T_511 |
Products that receive minor stretching
and straightening to comply with standard tolerances |
| T_52 |
Stress relieved by compressing after
soluition heat treatment (2.5% nominal permanent set
) |
| T_54 |
Stress relieved by combined stretching
and compressing (applies to die forgings that are
stress relived by restriking cold in a finish die) |
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