Spotlight On: Aluminium Grades

Known for its high strength-to-weight ratio and its lightweight, corrosion resistance and ease of machining properties, aluminium is the material of choice for castings in many industries.

It can be strengthened easily, offers good fluidity and can be used in complex part designs. However, one of the things that sometimes causes confusion is the grade of aluminium to go for when requesting aluminium investment castings. The grade of aluminium you require will depend entirely on its end use, how you would like it to look and how you want it to react to its environment once in place.

What Industries Use Aluminium Investment Castings?

Aluminium castings can be found in several sectors but are predominately found in the healthcare industry, food and dairy sector and in castings used for electronics, military and aerospace applications.

You find these castings in everything from levers, medical devices, electrical appliances, hand tools, automotive parts and more.

In addition to aluminium investment casting, you can choose to use the aluminium die casting process for your castings. Die casting is beneficial if you believe you will require an ongoing production of castings or have a very high volume of castings needed, as the mould will be reuseable following product development.

What Are the Different Grades of Aluminium?

To find aluminium metal used for any casting or application in its purest form is quite rare. This is because it lends itself well to being mixed with other elements, it can be weaker when used alone, and it is quite an expensive material. However, it's not impossible to use pure aluminium for castings. You will commonly find it mixed with different elements to give it other properties for the metals' intended use.

The different grades of aluminium are:

• 1XXX – aluminium in its truest form, at least 99% aluminium alloy
• 2XXX – an aluminium copper alloy
• 3XXX – an aluminium manganese alloy
• 4XXX – an aluminium-silicon alloy
• 5XXX – an aluminium magnesium alloy
• 6XXX – an aluminium, magnesium and silicon alloy
• 7XXX – an aluminium zinc alloy

The properties you require for your product will determine the grade of aluminium suitable for the application.

1XXX Grade Aluminium

The grades found in this series include 1050, 1100, 1200, 1350 and more. These are grades of aluminium in its truest form. It can be used to create castings but is more commonly found in sheet metal form.

It has high corrosion resistance and is suitable for thermal and electrical conductivity. The metal has excellent workability but low mechanical properties. It can be weak and soft and cannot be subjected to heat treatment to strengthen it.

2XXX Grade Aluminium

This aluminium is mixed with copper, with grades 2011, 2014 and 2024 the most common. Recommended for its strength and machinability, the 2XXX grades are tough, strong and hard. However, they are more likely to corrode and therefore are not recommended for applications with high exposure to oxidising elements. They can be better protected with coatings, though and heat treatment optimises their properties.

You can find aluminium copper alloys in use in the aerospace and industrial sectors.

3XXX Grade Aluminium

This is one of the most common aluminium alloys and is regularly used for general all-purpose applications, including the sides of cans, sheet metal and cooking utensils. It is formed by mixing aluminium with manganese which strengthens the metal and makes it resistant to oxidisation.

This alloy has a relatively low cost and can be used in many applications; it can handle the heat but not too much, so it is generally not used within ovens or anything where direct heat surrounds it.

4XXX Grade Aluminium

Aluminium silicon alloys are very popular. This is because mixing the metal with silicon improves its flexibility and makes it less brittle. This heat-tolerant alloy is often used for castings within the automotive and electronics industries as it can handle the heat and electricity passing through it.

5XXX Grade Aluminium

Aluminium combined with magnesium offers an excellent welding capability that is highly resistant to corrosion, meaning they are regularly found within marine applications, pressure valves and cryogenic tanks. They provide moderate strength and ductility, and some grades within the 5XXX series offer good aesthetic properties as they can retain their colour after anodising. Some grades within this series will also be mixed with other elements, including manganese or chromium.

6XXX Grade Aluminium

A mix of aluminium, magnesium and silicon makes for a highly malleable metal with above-average strength, great corrosion resistance and improved machinability. These alloys are usually found within the construction industry, with architects knowing the metal is durable and reliable. This series of aluminium can be heat treated to add strength.

7XXX Grade Aluminium

One of the most common aluminium alloys used in aeronautics and aerospace, the series 7XXX, is composed of aluminium and zinc. This mixture creates a steel-like strength from the metal but with much less weight for its applications. This light but very strong metal is often found in cars, sports equipment and more. Copper, chromium and magnesium are also found within the 7 series grades of aluminium.

8XXX Grade Aluminium

Other elements can be combined with pure aluminium to provide alloys that offer strength without losing conductivity. The most common is nickel and iron.

The Benefits of Aluminium

Aluminium is exceptionally versatile, is widely available as the third most plentiful element in the earth's crust, and can be recycled indefinitely.

What’s more, it can provide a controlled surface finish, so you know precisely what the aesthetics of your casting will be, and it is lightweight yet strong, a property that benefits many industries.

Aluminium investment castings can withstand very high operating temperatures compared to other alloys. The ability to conduct thermal and electrical energy makes the castings perfect in various applications.

If you require investment casting services and believe aluminium is the right metal for you, speak to a member of our team who will be happy to help you understand these grades more and which will work for your application. We have many years of experience delivering aluminium castings for various industries from our UK-based casting foundry and are confident we can help provide the right piece for your product.