Comparison of aluminium alloys

What is an aluminium alloy?

An aluminium alloy is created when pure aluminium is deliberately combined with other metals such as copper, magnesium, silicon or manganese. These additives change the mechanical and physical properties of the base material, so that the alloy can be tailored to specific requirements. By using alloying elements, strength, hardness, corrosion resistance and temperature behaviour can be specifically improved.

At the same time, certain alloys can be particularly well machined, welded or cast. Depending on the composition and heat treatment, different properties result that make components durable, resilient and functional. Aluminium alloys are divided into series that allow conclusions to be drawn about their main constituents and characteristic features – an important guide for architects, mechanical engineers, vehicle manufacturers or the aerospace industry.

Common aluminium alloys at a glance

Alloy	Main constituents	Properties	Typical applications
Al99.5 (1xxx series)	almost pure aluminium	very corrosion-resistant, soft, highly formable, low strength, excellent conductivity	Architecture, food industry, packaging, roofs, facades
AlMg3 (5xxx series)	magnesium	high corrosion resistance, good strength, good weldability, good machinability	Ships, tanks, car bodies, bridge construction, offshore applications
AlCu4Mg1 (2xxx series)	copper, magnesium	very high strength, limited corrosion resistance, difficult to weld, good hardening behaviour	Aerospace, vehicle construction, highly stressed components
AlSi10Mg (4xxx-5xxx series, casting alloy)	silicon, magnesium	very good castability, high strength, moderate corrosion resistance, temperature-resistant	Mechanical engineering, engine parts, technical components, prototypes
AlZn6MgCu (7xxx series)	zinc, magnesium, copper	extremely high strength, not very corrosion-resistant, difficult to machine, high fatigue strength	Aircraft construction, sports equipment, highly stressed structures

Criteria for choosing the right alloy

1. Mechanical load

Mechanical load is a central factor when selecting the suitable aluminium alloy. Components exposed to high forces, impacts or vibrations require alloys with maximum strength, such as the 2xxx or 7xxx series. Alloys of the 5xxx series offer a balanced combination of strength and machinability and are suitable for medium loads.

For components with low load, where flexibility, formability and ease of machining are the priority, alloys of the 1xxx series are optimal. The right choice ensures not only safety, but also the durability and functionality of the component over its entire life cycle.

2. Corrosion resistance

Corrosion resistance is decisive for the suitability of the alloy in damp, saline or chemically aggressive environments. Alloys of the 1xxx and 5xxx series are particularly resistant to oxidation and rust, as the high aluminium content or magnesium additions promote the formation of protective layers.

High-strength alloys of the 2xxx or 7xxx series are more sensitive to corrosion and may require additional protective measures such as coatings, paints or anodising to ensure a long service life. Observing the corrosion requirements is essential for planning durable and safe components.

3. Machinability and processing options

Machinability determines how easily the alloy can be milled, drilled, cut or welded. Alloys such as Al99.5 or AlMg3 are easy to machine and easy to weld, which enables cost-effective production with standard tools. High-strength alloys require specialised machines, experienced technicians and, if necessary, special heat treatments to avoid stress cracks or deformation during processing.

Precisely matching the choice of alloy to the planned manufacturing processes is decisive in order to ensure efficiency, precision and compliance with quality standards.

4. Temperature resistance

For applications in which aluminium alloys are exposed to high temperatures, stability under thermal load is of great importance. Alloys such as AlSi10Mg or certain 5xxx alloys retain their strength, shape and mechanical properties even at high temperatures.

This is particularly important for components in engines, machines or in aerospace, where temperature changes and thermal stress occur regularly. The right choice of alloy prevents material fatigue, deformation and loss of performance.

5. Budget and cost-effectiveness

The cost factor plays an essential role in alloy selection. Pure aluminium is inexpensive, but offers lower mechanical resilience. High-strength alloys, which are necessary for highly stressed components, have a higher price. When selecting, in addition to the acquisition costs, long-term factors such as service life, maintenance effort and manufacturing costs should also be taken into account.

Economically sound planning ensures that the component meets the technical requirements and can at the same time be produced cost-efficiently.

Aluminium alloys in practice

In practice, the choice of aluminium alloy depends heavily on the requirements of the respective project. In mechanical engineering and vehicle construction, alloys such as AlMg3 or AlCu4Mg1 are frequently used, as they offer a good ratio of strength and corrosion resistance. For highly stressed structures in aerospace, sports equipment construction or special vehicles, alloys of the 2xxx and 7xxx series are suitable, as they deliver extremely high strength and good fatigue values, but require special machining processes.

The manufacturing processes also influence the choice of alloy: sheet and profile alloys can be easily milled, turned, drilled or welded, while casting alloys such as AlSi10Mg are ideal for complex shapes and prototypes. High-strength alloys benefit from heat treatments that further improve their mechanical properties. For outdoor applications or in contact with aggressive media, corrosion resistance is a decisive criterion – here magnesium alloys (5xxx series) score with their resistance to moisture, salt water or chemical influences.

In architecture and food technology, alloys of the 1xxx or 5xxx series are preferred, as they are easy to process, highly formable and very corrosion-resistant. At the same time, costs, weight and processability must be brought into harmony. A practical selection of the aluminium alloy therefore takes into account not only the technical requirements, but also manufacturing options, environmental conditions and economic aspects in order to ensure the efficiency and durability of the project.

Tips for your project

1. Check the load requirements and plan the alloy accordingly.
2. Take the corrosive environment into account, especially with moisture, salt water or chemical contact.
3. Plan the machinability, weldability and processing methods in advance.
4. Pay attention to temperature resistance if the component is exposed to high temperatures.
5. Calculate the material costs at an early stage and compare price and performance.
6. Seek expert advice when it comes to highly stressed or critical components.

Decision aid: Which aluminium alloy suits my project?

Requirement	Low load	Medium load	High load	Damp / corrosive environment	Easy machining / welding
Al99.5 (1xxx series)	✅ Ideal	⚠ Less suitable	❌ Not suitable	✅ Very good	✅ Very good
AlMg3 (5xxx series)	⚠ Suitable	✅ Good	⚠ Medium	✅ Very good	✅ Good
AlCu4Mg1 (2xxx series)	❌ Not suitable	✅ Good	✅ High	⚠ Limited	⚠ Difficult
AlSi10Mg (casting alloy)	✅ Good	✅ Good	⚠ Medium	✅ Good	⚠ Limited
AlZn6MgCu (7xxx series)	❌ Not suitable	⚠ Medium	✅ Very high	❌ Less suitable	❌ Difficult to machine

Usage notes:

1. Check the load: Choose according to the mechanical requirements of your component.
2. Corrosive environment: For outdoor applications or contact with water, prefer magnesium alloys.
3. Machinability: If CNC milling, drilling or welding is required, observe the alloy properties.
4. Temperature and ambient conditions: Check whether the material is suitable for hot or chemically aggressive environments.
5. Combinations: Often a compromise between strength, corrosion protection and machinability is optimal.

Conclusion

Choosing the right aluminium alloy is a central factor for the success of your project. Different alloys offer specific advantages with regard to strength, corrosion resistance, machinability, temperature resistance and costs. A well-founded selection makes it possible to precisely match components to the mechanical requirements and ambient conditions.

This is how you can ensure that your component withstands the loads, is durable and can be manufactured economically. Plan the alloy selection carefully, take manufacturing processes, material properties and budget into account, and seek expert advice for complex or highly stressed projects. With the right aluminium alloy, you lay the foundation for quality, safety and efficiency in your project.

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Frequently asked questions about aluminium alloys

What is the difference between pure aluminium and alloy materials? Pure aluminium (e.g. Al99.5) consists almost exclusively of aluminium and is very soft, highly formable and corrosion-resistant, but comparatively weak in strength. Aluminium alloys contain deliberately added other metals such as copper, magnesium, silicon or zinc, whereby mechanical properties, hardness, corrosion resistance and machinability can be specifically improved.

Which aluminium alloy is best suited for highly stressed components? For heavily stressed components, alloys of the 2xxx and 7xxx series are optimal, as they offer very high strength and good fatigue resistance. However, these alloys require special machining techniques, e.g. for milling, welding or heat treatment.

Which alloys are particularly corrosion-resistant? Alloys of the 1xxx and 5xxx series (e.g. Al99.5 or AlMg3) are characterised by high corrosion resistance. They are ideal for outdoor applications, damp environments or contact with salt water, such as in shipbuilding or facades.

Can every aluminium alloy be welded? No. Pure aluminium and alloys of the 5xxx series can be welded well. High-strength alloys of the 2xxx and 7xxx series require special processes and trained specialists in order to avoid cracks or material damage.

Which alloys are well suited for CNC machining? Al99.5, AlMg3 and AlSi10Mg are particularly suitable for milling, drilling and turning. High-strength alloys require harder tools and special machine parameters.

How does the budget influence the choice of alloy? Pure aluminium is more cost-effective and sufficient for many applications. High-strength alloys are more expensive, but offer the necessary performance for stressed components. The choice should be technically sensible and economically balanced.

Are there alloys that are particularly temperature-resistant? Alloys with silicon or magnesium content (e.g. AlSi10Mg or AlMg3) withstand higher temperatures and retain their strength under heat, making them suitable for engine parts or technical components.

How do I choose the optimal alloy for my project? Take mechanical load, corrosive environment, machinability, temperature requirements and budget into account. A combination of these criteria as well as expert advice for critical components leads to the optimal selection.