Aluminium must be mixed with other elements to give it the properties it needs to be useful in engineering applications. In its pure form, it’s soft and pliable, but it becomes stronger, harder and more versatile when it’s alloyed.
The fabrication process and elements added not only affect the properties of the final product, but also the applications a particular aluminium alloy is most appropriate for. Aluminium grades are used to differentiate between different types of aluminium alloys and signal their best uses.
How are the different aluminium grades classified?
Aluminium grades are classified according to the amount and type of metal that is used to produce the alloy. The way in which the alloy is formed—either cast or wrought—also has an effect on aluminium gradings.
The four-digit naming convention used to classify all aluminium alloys indicates the grade or series of aluminium as well as whether it is cast (XXXX) or wrought (XXX.X). Wrought alloys are graded from 1 to 7, while cast alloys go from series 1 to 8, with the exception of series 6.
|Wrought alloys||Cast alloys|
|1||99% pure aluminium||99% pure aluminium|
|2||Copper||Copper and magnesium|
|3||Manganese||Silicone, copper and/or magnesium|
|6||Silicone and magnesium||–|
The most common aluminium grades and uses
There’s a grade of aluminium for every application. From smart devices to home appliances, window frames and electrical wiring—and the trains, ships and trucks that are used to transport those goods around the world—this versatile metal has seemingly endless uses.
Here are some of the most common aluminium grades and their applications.
Grade 1 aluminium has a purity of 99% or greater, making it the softest and most malleable of the common aluminium alloys. Although it is not heat treatable, 1100 aluminium has a high corrosive resistance and is a great insulator. It also has good machinability when it’s hard-tempered.
- Electrical wiring
- Heat insulators
- Spun hollow ware (e.g. metal bowls)
- Chemical handling
- Heating, ventilation and air conditioning units
The addition of copper and manganese makes 3003 aluminium a relatively strong, inexpensive material with good formability and workability. These factors, as well as its uniform appearance and high resistance to corrosion, allows 3003 aluminium to be used in a broad range of moderate-strength applications. However, it isn’t heat treatable.
- Sheet metal fabrications
- Cooking utensils
- Food containers
- Pressure vessels
- Chemical equipment
With the addition of magnesium, 5052 is one of the most versatile non-heat treatable sheet and plate aluminium alloys. It’s durable and, when anodised, extremely resistant to corrosion, making it especially good for marine applications. Although it isn’t as strong as some of the other common alloys, 5052 aluminium has a high rate of work hardening and can be drawn.
- Fuel tanks
- Hydraulic tubes
- Marine equipment
- Medical equipment
- Fans and fan blades
- Non-critical automotive parts
One of the strongest alloys, 6061 aluminium is the least expensive and most versatile of these metals. The addition of magnesium and silicone means that 6061 aluminium is heat treatable and can be anodised and hardened after forming. Its post-heat treated strength is equal to low-carbon steel, but it retains higher corrosion resistance and a better strength-to-weight ratio.
- Architectural applications
- Structural framing
- Fire ladders
- Bridge components
Alloyed with magnesium and silicone, 6063 aluminium is extremely strong and has a lower melting point than other forms of the metal. Although it has the same constituents as 6061 aluminium, this heat-treatable alloy has a low strength-to-weight ratio. However, 6063 aluminium has a more attractive finish and can be anodised to increase corrosion resistance.
- Electrical components
- Electrical conduit
- Irrigation pipes and tubes
- Door frames
- Motor vehicles
What to consider when choosing aluminium grades
The aluminium grade you need will depend on what you intend to use the material for. Some alloys have an excellent strength-to-weight ratio, which is great for heavy-duty applications like structural framing. Others have a more uniform appearance, which is better for decorative uses.
When choosing a type of aluminium alloy to work with, consider the end use as well as the processing that the material will have to undergo to make your product.
Here are a few factors to keep in mind when selecting your aluminium:
- Format: Aluminium alloys come in various formats, including sheets, pipes, rods and plates, which will affect your ability to form, work and machine the metal.
- Formability and workability: Formability and workability refer to a metal’s ability to be shaped without cracking or breaking down and affects the products you can fashion.
- Weldability: Applications where the joining of aluminium components to one another or other metal components is necessary will require an alloy with good weldability.
- Machining: The alloy’s ability to be shaped by removing material depends on the strength, hardness and malleability of the aluminium grade you choose.
- Strength: While some applications may require an extremely strong alloy (e.g. aircraft fabrication), a low-strength aluminium may work for others (e.g. kitchenware).
- Heat treating: The workability of some alloys can be increased through heat treating. This process also strengthens and hardens aluminium that can’t be work-hardened.
- Corrosion resistance: Aluminium grades vary in their ability to resist corrosion; the final application of your product will determine how important this factor is.
- End use: All of the above factors must be weighed against one another to ensure you make the best choice of alloy for your intended application.