1. Alloys
2. Manufacturing
3. Product Forms

1. Alloys

The aluminum industry distinguishes one alloy from another through a standardized numbering system. Wrought alloys use a four-digit designation while cast alloys use three-digits. Various prefixes and suffixes are also used in both classes of aluminum.

Wrought Alloys

The first of four-digits used to identify a wrought aluminum alloy signifies the principal alloying element. For example, the fifth digit in a 5000-series aluminum alloy indicates magnesium as the principal alloying addition. The second digit refers to some particular modification of the original alloy composition. A suffix consisting of a dash followed by a series of letters and numbers define the temper, indicating certain properties and the process used to obtain them.

These suffixes begin with three possible letters:

• T - indicates a heat-treatable alloy
• H - indicates a non-heat-treatable alloy with final properties achieved instead by mechanical working such as cold rolling
• O - indicates annealed material (not heat treated)

Cast Alloys

The first number in a three-digit cast alloy designation also indicates the principal alloying element. However, this system does not parallel the one used for wrought alloys. (The first number indicates that the principal alloying element is manganese in wrought alloys and silicon in cast alloys.) Modifications to a cast alloy makeup are indicated by a letter prefix. Dash, letter and number suffixes are also used to describe the process in which to obtain particular mechanical properties.

In both wrought and cast aluminum materials, the particular alloying elements are critical to recycling but temper states are not. The following is a list of alloys that may be encountered and their typical automotive applications.

Wrought Alloy Series

1000 Series

With aluminum of 99 percent or higher purity, these compositions are characterized by excellent corrosion resistance, high thermal and electrical conductivity, low mechanical properties and excellent workability. Moderate increases in strength may be obtained by strain hardening.

2000 Series

Copper is the principal alloying element in this group. When heat-treated, the mechanical properties are similar to, and sometimes exceed, those of mild steel. Artificial aging may be employed to increase strength. These alloys in the form of sheet are often clad with a high-purity 6000 or 7000 series alloy. This provides physical and electrolytic protection to the core material, and greatly increases resistance to corrosion.

3000 Series

Manganese is the principal alloying element in this group. These alloys are not heat treatable. They have a superior combination of corrosion resistance and formability.

4000 Series

Silicon is the major alloying element in this group. Silicon is used in wrought alloys to lower the melting range without causing brittleness. Aluminum-silicon alloys are used to make welding wire and as cladding alloys for brazing sheet, where a lower melting range than that of the base metal is required. One application in addition to joining and brazing filler applications is alloy 4032 which has good wear resistance, and thus it is well suited to the production of forged engine pistons.

5000 Series

Magnesium is one of the most effective and widely used alloying elements for auto aluminum, and is the principal element in the 5000 series alloys. When it is used as the major alloying element or combined with manganese, the result is a moderate- to high-strength, non-heat-treatable alloy. Alloys in this series are readily weldable and have excellent resistance to corrosion, even in marine applications.

6000 Series

Alloys in this group utilize magnesium and silicon in various proportions to form magnesium silicide, making them heat treatable. A major alloy in this series is 6061, one of the most versatile of the heat-treatable alloys. The magnesium-silicon (or magnesium-silicide) alloys possess good formability and corrosion resistance with high strength.

7000 Series

Zinc is the principal alloying element in this group. When it is combined with smaller percentages of magnesium and, in some cases copper, it results in heat-treatable alloys of very high strength.

Casting Alloys

Aluminum alloy castings can be produced by virtually all casting processes in a very large range of compositions possessing a wide variety of useful engineering properties. The choice of a specific casting alloy depends on the chosen casting process (which include: sand, permanent mold, die, lost foam or squeeze), the product design, the required properties of the product and other relevant factors.

2. Manufacturing 

The manufacturing processes of aluminum include:

• Machining
  The broad term used to describe removal of material from a workpiece in the form of chips by covering several different processes such as; cutting, grinding, milling, drilling, tuning, etc. The same lathes, drill presses, milling machines and other metal-removal equipment commonly found in metalworking shops are routinely used to shape aluminum alloys. The metal may be turned, bored, milled or machined at the maximum speeds of which most machines are capable.
• Joining
  The process of fusing aluminum to other metal mediums through welding. Automotive aluminum can be joined by most of the same processes used to join steel. Improved materials, equipment and processes have made aluminum joining effective and reliable. Weld bonding, in particular, is especially well suited to aluminum, providing enhanced structural stiffness and excellent durability.
• Stamping/Blanking
  The process of cutting up a large aluminum sheet into workable pieces. Aluminum sheets are blanked and formed by stamping using the same equipment as is used today for steel. Clean-cut edges from a correct punch/die clearance are essential for developed blank production. Stamping die clearances, die radii and blank hold-down force must all be set-up for the forming characteristics of automotive aluminum.
• Bending/Hydroforming
  Auto aluminum's manufacturability and workability have been proven in many ways, including bending and hydroforming processes that offer ease of tooling, cost-effectiveness, and a high degree of flexibility.
• Finishing
  The process of coating aluminum to protect its surface. The cost of finishing to today's standards of corrosion and paint performance is high. A much simpler and less expensive finishing system can be used with aluminum than with mild or galvanized steel due to its greatly enhanced corrosion resistance.

3. Product Forms

Aluminum product forms include:

• Rolled products
  Aluminum sheet applications include heat exchangers, heat shields, bumper stock as well as closure sheet and structural sheet for complete body assemblies.
• Extruded products
  Aluminum alloy extrusions offer designers unparalleled freedom from standard shape restrictions. Applications include: space frames, suspension, seat frames and rails, sun roofs, window and door frames, and aluminum/aluminum metal matrix composite drive shafts.
• Cast products
  Die castings are used for pistons, transmission housings, and suspension components and aluminum metal matrix brake drums and rotors. Sand castings are used for engine blocks, cylinder heads and manifolds. Structural castings are used for cross members and body structures while, structural die castings are used for body structures. Structural permanent mold castings are used for body structures and sub frames, and permanent mold castings for wheels used on 45 percent of new passenger vehicles today.
• Forged products
  Forged aluminum products include structural forgings for chassis and suspension parts, forged wheels, and airbag components. Aluminum forging technology is notable for the ease with which unusual shapes and extremely large components with excellent mechanical properties can be obtained.