Why the Choice of Aluminium Alloy Is Critical
Aluminium is the most widely processed non-ferrous material in CNC machining. But behind the term "aluminium" lies a multitude of alloys with very different properties. The right alloy choice affects machinability, strength, corrosion resistance and ultimately the cost of your component.
In this article, we compare the most important aluminium alloys for CNC machining and provide practical recommendations.
Understanding the Alloy System
Wrought Alloys (1000–7000 Series)
Aluminium alloys are classified by their primary alloying element into series:
- 1000 series: Pure aluminium (99%+ Al) — soft, excellent conductivity
- 2000 series (AlCu): Copper alloys — high strength, aerospace
- 5000 series (AlMg): Magnesium alloys — seawater resistant, weldable
- 6000 series (AlMgSi): Universal alloys — good machinability, anodisable
- 7000 series (AlZnMg): Zinc alloys — highest strength
Age-Hardenable vs. Non-Age-Hardenable Alloys
An important distinction: age-hardenable alloys (2000, 6000, 7000) can be hardened by heat treatment. Non-age-hardenable alloys (1000, 3000, 5000) are strengthened by cold working. For machining, this means: age-hardenable alloys in T6 or T651 condition machine better than in the soft state.
The Most Important Alloys in Detail
AW-6082 (AlMgSi1) — The All-Rounder
The most widely used alloy in CNC machining. Offers an excellent balance of strength, machinability and price. Ideal for machine components, fixtures and general structural parts.
- Tensile strength: 290–340 MPa (T6)
- Machinability: Very good
- Anodising capability: Good, uniform layer thickness
- Weldability: Good (MIG/TIG)
AW-7075 (AlZnMgCu) — The High-Strength Choice
The strongest standard aluminium alloy with tensile strengths comparable to some steels. Frequently used in motorsport, aerospace and for highly loaded components.
- Tensile strength: 510–570 MPa (T6)
- Machinability: Good, but requires sharp tools
- Anodising capability: Moderate (yellowish tint possible)
- Weldability: Limited
AW-5083 (AlMg4.5Mn) — The Seawater-Resistant Choice
The preferred choice for marine applications and corrosive environments. Not age-hardenable, therefore lower strength than 6082 or 7075.
AW-2024 (AlCuMg) — The Aerospace Standard
The classic aerospace alloy with high strength and good fatigue resistance. Corrosion protection through cladding (Alclad) or surface treatment is required.
Machining Recommendations by Alloy
Each alloy requires adapted tools and cutting parameters:
- AW-6082: Standard tools, vc = 200–400 m/min, high feed rates possible
- AW-7075: Sharp, polished tools, vc = 250–500 m/min, good chip breaking
- AW-5083: Beware of built-up edge, good cooling important
- AW-2024: Similar to 7075, slightly lower cutting speeds
Frequently Asked Questions (FAQ)
Which aluminium alloy machines best?
AW-2011 and AW-6082 are considered particularly machinable. AW-2011 was specifically developed as a free-cutting alloy and delivers excellent surfaces and short chips.
Can different alloys be distinguished visually?
No — the differences are not visible to the naked eye. The alloy must be identified via material certificates or spectral analysis.
Is AW-7075 harder to machine than AW-6082?
Not harder, but different. AW-7075 requires sharper tools and higher cutting speeds but delivers very good chip breaking and clean surfaces.
Conclusion: The Alloy Determines Success
Choosing the right aluminium alloy is one of the most important decisions in component design. It affects not only mechanical properties but also manufacturing costs and achievable quality.
Unsure about alloy selection? Contact us — we advise you based on your application and help with optimal material selection.