Representation method of aluminum alloy

Aluminum alloys are represented by four-digit numbers plus some symbols, such as 5083-H112, 7075-T73, etc.

In terms of representation, the difference between forged aluminum alloys and cast aluminum alloys is also obvious.

Cast aluminum alloys have a decimal point in the first 4 digits, while wrought aluminum alloys have no decimal point.

For example, 1xxx, 3xxx, 5xxx, 7xxx, etc. refer to wrought aluminum alloys, while 1xx.x, 3xx.x, 5xx.x, 7xx.x, etc. refer to cast aluminum alloys.

Because most of the forged aluminum alloys are used in practical engineering, next, I mainly focus on forged aluminum alloys.

• The first digit indicates the type of aluminum alloy, consisting of 1-9, and different numbers indicate different alloy compositions.
• The second number indicates the modification of the alloy composition, 0 indicates the original composition, 1 indicates the first modification, 2 indicates the second modification, and so on, indicating the difference in the content of different alloy elements. For example, 7075 represents the original aluminum-zinc alloy, 7175 and 7475 represent the aluminum-zinc modified alloy, and 7175 and 7475 are the modified grades of 7075.
• The 3rd and 4th digits denote a specific alloy within that family of alloys. The values of these numbers have no special meaning.

Next, we will introduce the meaning of the model numbers of aluminum alloys one by one.

• 1xxx series

Class 1 aluminum alloys are not real aluminum alloys, because their aluminum content is 99%, which is commercial pure aluminum.

In terms of machinery, this type of alloy has good ductility. For example, 1100 is often used for sheet metal, and common aluminum foil packaging for medicine and food is also made of Class 1 alloy.

In addition, Class 1 alloys have good corrosion resistance, workability, and can increase their strength by work hardening.

These alloys are widely used in the field of power transmission because of their excellent electrical and thermal conductivity.

• 2xxx series

The main alloying element of Type 2 alloys is copper with a small amount of magnesium.

Because copper dissolves in aluminum at high temperatures, such alloys respond to solid solution strengthening and are called heat treatable aluminum alloys.

After heat treatment, it can have very good strength, comparable to mild steel.

Of course, because it contains copper, it is also more prone to corrosion.

2024 is the typical and most widely used Class 2 aluminum alloy.

• 3xxx series

The main alloying element of Class 3 aluminum alloys is manganese.

These alloys are moderately strong and have excellent machinability.

For example, the 3003 aluminum alloy in this grade is often used in heat sinks because of its good machinability.

Another example is 3004 aluminum alloy, which has good ductility and workability, and is often used in the manufacture of cans.

• 4xxx series

The main alloying element of Class 4 aluminum alloys is silicon.

The addition of silicon lowers the melting point without affecting ductility, so these alloys are often used as welding wires to join other aluminum.

Additionally, 4-series alloys are commonly used in construction because of their aesthetically pleasing oxide layers. The most representative is 4047, which has good thermal conductivity, electrical conductivity and corrosion resistance.

Such alloys are generally not heat treatable, but depending on the silicon content, and the composition of other alloying elements, some can be heat treated to some extent.

• 5xxx series

The main element of the 5xxx series alloys is magnesium, and in certain alloys, a small amount of manganese is also contained.

These alloys are strain hardenable, easy to weld, and have excellent corrosion resistance, so they can be used in marine environments like ship hulls, gangways and other marine equipment.

For example, 5052 alloy has good seawater corrosion resistance and excellent machinability, and is often used in marine ships, while 5083 can be used in tanks and fighters, and 5005 is often used in building structures.

• 6xxx series

The main alloying elements of 6 series aluminum alloys are magnesium and silicon, which will synthesize Mg2Si during solution heat treatment.

This type of alloy can be increased in strength by heat treatment. Although not as strong as the 2xxx and 7xxx series aluminum alloys, it combines good strength, workability, weldability, formability and corrosion resistance.

Extruded 6-series alloys are the first choice for machinery and building structures.

For example, 6061 aluminum alloy is the most flexible of heat treatable aluminum alloys, and it retains most of the excellent properties of aluminum, so it is also the aluminum alloy we use most frequently in our designs. This grade has a wide range of mechanical properties and corrosion resistance, has excellent machinability in the annealed condition, can be processed using conventional methods, and it can also be welded.

• 7xxx series

The main alloying element of Class 7 aluminum alloys is zinc, usually with a certain amount of copper and magnesium.

Because of the use of zinc, these alloys are the strongest of all wrought alloys and can even surpass some steels in strength.

Because of this, Group 7 alloys are often used in the aircraft industry. Although the addition of zinc also reduces its workability, its excellent strength makes up for these shortcomings.

7075 aluminum alloy, for example, is ideal for highly stressed parts because of its excellent weight-to-strength ratio. And can perform forming processing, heat treatment and other operations as needed.

• 8xxx series

Type 8 aluminum alloys use less commonly used elements as their alloying elements, such as lithium, tin, or iron.

Such alloys are generally used in occasions with specific requirements, such as high temperature performance, lower density, higher stiffness and other requirements.

For example, aluminum-lithium alloy 8090-T8771 is used for large turntables with low rotational inertia and high rigidity for high-speed rotation.

Group 8 alloys are also commonly used in helicopter components, and other aerospace applications.

• 9xxx series

The 9 series of aluminum alloys is currently blank. In order to cope with the emergence of aluminum alloys containing other metals, the International Aluminum Plate and Strip Federation uses the 9xxx series as a backup series.