Aluminium Alloys: Go-to materials for automotive, aerospace, and more

Aluminium is a common and popular metal that is found in a wide range of products: automotive parts, aerospace components, boat and marine equipment, consumer electronics including smart phones, industrial machinery, heating, ventilation, air conditioning (HVAC) systems, the list goes on.

Engineers and product designers frequently use aluminium and its alloys to design both prototypes and end-use parts. This blog looks at why aluminium is so commonly used, why there are so many aluminium alloys, and takes a brief glimpse at the main alloys we use here at Protolabs.

Why is Aluminium so popular?

Aluminium has a high strength-to-weight ratio, making it lightweight, yet strong and flexible. It’s also affordable, corrosion-resistant, and works well in a multitude of applications.

Aluminium alloys are often used in cars because of the material’s versatility. Aluminium’s formability and corrosion resistance make it easy to work with and shape, but its structural soundness addresses the most important requirement for car bodies. Strength is important, but car bodies must be lightweight, affordable to produce, resistant to rust, and have the attractive qualities consumers seek, such as exceptional surface finishing characteristics. Aluminium nicely fits the bill.

The same holds true with aerospace parts. Aluminium alloys are often a preferred material for aerospace designs and required by engineering, again because of aluminium’s corrosion-resistance properties and high strength capabilities. Compared to steel it is a lightweight option, and an ideal material for a wide range of aircraft components and aerospace applications.

Lightweighting is a core need of both the automotive and aerospace industries. It helps reduce emissions and meet improved fuel economy standards. 

For aerospace, the use of aluminium alloys dramatically decreases the weight of an aircraft because it is significantly lighter than steel, allowing aircrafts to either carry more weight or increase fuel efficiency. Weight reduction is closely related to fuel efficiency. Along these lines, common applications in aerospace abound—many, but not all, of which, are metal: fuel delivery, heat exchangers, manifolds, turbo pumps, liquid and gas flow components, conformal cooling channels, fasteners, and more.

So why are there so many metal alloys?

Aluminium, as a pure element, presents many desirable properties. However, by itself, aluminium might not be strong enough for a high-durability use or purpose. Aluminium can be combined with other elements to form alloys, which are more durable and more suitable for industrial applications.

What do the numbers in the alloy name signify? There are 4 common ways to classify metals in Europe, this is how to interpret them:

EN Standard:

The aluminium series names elements with four numerical digits where the first digit represents the principal alloying element, the second digit indicates a modification of a specific alloy, and the third and fourth digits are arbitrary numbers assigned to specific alloys in the series. For example, 6082 is in the 6000 series (and is almost identical to 6061).

Temper condition

Irrespective of the temper condition, the alloys chemical composition stays the same. In our example T651 is often just referred to as T6 (which means it has been solution heat treated and artificially aged). Heating, stretching and aging (controlled heating or cooling) are all methods used to improve the combination of strength and toughness.

EN 10027 / DIN 1745

Each metal is given a unique 4-digit code: Steels range from 1.000 to 1.970. Copper alloys in the 2.000 range. Aluminium alloys are in the 3.000 range.

ISO

This refers to the chemical composition. For example Aluminium 6082 is AlSi1MgMn, the first alloy is the balance (or remainder, so often the biggest %), the following numbers are the % of each alloying element, with no number if it is < 1%. Hard to explain easier to see:

• AlSi1MgMn = ~99% Aluminium, Silicon (<1%), Magnesium 1%, Manganese (<1%).
• Ti6Al4V = ~90% Titanium, 6% Aluminium, 4% Vanadium.

For the exact chemical composition, including trace elements refer to our data sheets.

Aluminium 6082-T651 | 3.2315 | AlSi1MgMn

The most commonly used aluminium alloy at Protolabs, if you need an excellent all-rounder this is a good choice. Aluminium 6082 is used for CNC machining and is generally selected where welding or brazing is required or for its high corrosion resistance in all tempers. Formability is excellent in O temper and good in the T4 temper. T6 temper is stronger. It is used for aerospace, automotive parts, boat and marine gear, furniture, consumer electronics, sports equipment, and many more. Predominantly aluminium; alloyed with up to 6.1% Zinc, 2.9% magnesium 2% copper as well as other elements.

Aluminium 5083-H111 | 3.3547 | AlMg4.5Mn0.7

This alloy has good workability, very good corrosion resistance, high-fatigue strength, weldability, and moderate strength. This makes it perfect for use in aircraft fuel/oil lines, fuel tanks, other transportation areas, automotive, marine, appliances and lighting, wire, and rivets. Predominantly aluminium; alloyed with up to 4.9% magnesium, 1% manganese and 0.4% iron as well as other elements.

Aluminium 7075-T7351 | 3.4365 | AlZn5.5MgCu

Solution heat treatment then specially artificially aged for resistance to stress corrosion. By taking T6 and over aging, it loses a little strength but increases its toughness. This makes it more durable and well suited to aerospace, extremely low-temperature applications such as satellites and cryogenics.

Aluminium 7075-T651 | 3.4365 | AlZn5.5MgCu

7075 has been the standard 7000 series aerospace alloy, with a good balance of properties required for aerospace applications, particularly where high static loads occur. Predominantly aluminium; alloyed with up to 6.1% Zinc, 2.9% magnesium 2% copper as well as other elements.

Used for aircraft fittings, gears, shafts, valves, mould tooling, bicycle equipment, camping and sports gear because of its lightweight yet strong characteristics. Adding chromium to the mix to develop good stress-corrosion cracking resistance and a higher fatigue strength of 160 MPa.

Aluminium 2024-T351 | 3.1355 | AlCu4Mg1

An aerospace grade, 2000 series has a lower ultimate tensile strength (UTS) than 7075 but better elongation and good fatigue strength. This makes it ideal for applications where high cyclic fatigue resistance is required or structures that are in tension.

Mostly aluminium; alloyed with up to 4.9% copper, 1.8% magnesium and 0.9% manganese as well as other elements. T351 refers to the temper T3: Solution heat treated, cold worked and naturally aged. Similar to T4 this gives good formability, at a slightly lower hardness and Ultimate Tensile Strength (UTS). Higher fatigue strength of 140 MPa.

Aluminium casting 3000 series | 3.2381 | AlSi10Mg

A mainstay of our 3D printing direct metal laser sintering (DMLS) process, this is comparable to the 3000 series alloy that is used in casting and die-casting processes. It has good strength-to-weight ratio, high temperature and corrosion resistance, and good fatigue, creep, and rupture strength. AlSi10Mg also exhibits good thermal and electrical conductivity. Components parts built in AlSi10Mg are stress relived by heat treatment after laser welding.

For questions on aluminium alloys, other materials, or any of our manufacturing services at Protolabs, please contact an Application Engineer at customerservice@protolabs.co.uk or +44(0) 1952 683047.