Aluminium

Aluminium is roughly one-third the weight of steel while offering excellent corrosion resistance, good strength-to-weight ratio, and outstanding machinability. It is the material of choice when weight reduction, natural corrosion resistance, or anodising is required. Aluminium alloys are divided into series based on their primary alloying element. For fabrication, the 5xxx series (magnesium alloys) and 6xxx series (magnesium-silicon alloys) are most relevant. The 5xxx series is strengthened by cold working and is the standard for sheet metal and marine applications, while the 6xxx series is heat-treatable and preferred for CNC machined parts.

Key Properties

Density	2.66–2.70 g/cm³
Tensile Strength	160–317 MPa (varies by alloy)
Melting Point	~660°C
Thermal Conductivity	High (~205 W/m·K)
Electrical Conductivity	Good (~60% of copper)
Magnetic	No

Grades

Property	5005	5052	5083	6061-T6
Tensile Strength	160 MPa	230 MPa	317 MPa	310 MPa
Yield Strength	110 MPa	195 MPa	228 MPa	276 MPa
Elongation	8%	12%	16%	12%
Density	2.70 g/cm³	2.68 g/cm³	2.66 g/cm³	2.70 g/cm³
Weldability	Excellent	Excellent	Excellent	Fair (loses temper)
Corrosion Resistance	Excellent	Excellent	Excellent (marine)	Good
Machinability	Poor	Fair	Fair	Excellent
Anodising	Excellent	Good	Fair	Excellent
Heat Treatable	No	No	No	Yes
Typical Use	Architectural, anodised panels	General sheet metal fabrication	Marine, structural	CNC machined parts, structural

5005

A low-strength alloy primarily used for architectural and decorative applications. Produces the most consistent and attractive anodised finish of all common alloys. Ideal for facades, signage, and trim where appearance is paramount.

5052

The standard alloy for aluminium sheet metal fabrication. Good strength, excellent formability, and very good corrosion resistance. Available in H32 (quarter hard) temper for most laser cutting and bending work. The go-to choice for brackets, enclosures, panels, and general fabricated parts.

5083

The premier marine aluminium alloy. Highest strength of the non-heat-treatable alloys with outstanding saltwater corrosion resistance. Used extensively in boat building, marine fittings, pressure vessels, and structural applications requiring high strength and weldability.

6061-T6

The most versatile heat-treatable aluminium alloy. In the T6 temper, it offers high strength and excellent machinability, making it the standard choice for CNC machined components, jigs, fixtures, and structural members. Anodises well with consistent colour. Welding creates a heat-affected zone that reverts to lower temper, so post-weld heat treatment is needed for full strength recovery.

Available Thicknesses

Sheet (laser cutting): 1.6mm, 2mm, 3mm, 4mm, 5mm, 6mm. Plate and billet (CNC machining): 6mm, 10mm, 12mm, 20mm, 25mm, 32mm, 38mm, 50mm. Round bar and extrusions also available for machining work.

Fabrication Notes

Aluminium laser cuts well but requires nitrogen assist gas for clean, oxide-free edges. Cutting speeds are generally faster than stainless steel but require careful parameter control to avoid burring. Bending is straightforward in annealed or H32 temper; harder tempers may crack on tight radii. 5xxx series alloys are strengthened by cold working (strain hardening). Temper designations: O (annealed/soft), H32 (quarter hard), H34 (half hard). These alloys cannot be heat treated for additional strength. 6xxx series alloys are strengthened by solution heat treatment and ageing. T4 (solution treated, naturally aged), T6 (solution treated, artificially aged — peak strength), T651 (T6 plus stress relieved). 6061-T6 is the standard for CNC machined parts due to its excellent machinability and high strength. Welding 6061-T6 creates a heat-affected zone that reverts to T4 or O temper, significantly reducing strength locally. Post-weld heat treatment is needed for full strength recovery. For welded structural applications, 5052 or 5083 are often preferred as they do not suffer this issue.

Surface Finishes

Anodising (clear, black, colours), hard anodising, powder coating, brushed finish, polished, chemical conversion coating (Alodine/Alocrom). 5005 and 6061 produce the most consistent anodised colour. Raw aluminium forms a natural oxide layer that provides moderate corrosion protection without any coating.

When to Choose Aluminium

Choose aluminium when weight reduction is important, natural corrosion resistance is needed (without coatings), the part will be anodised, or excellent machinability is required. Use 5052-H32 for sheet metal and laser cutting, 5083 for marine applications, and 6061-T6 for CNC machined parts and structural extrusions.

Limitations

Aluminium has lower absolute strength than steel (though a better strength-to-weight ratio). It is more expensive than mild steel per kilogram. Welding 6061-T6 significantly reduces strength in the heat-affected zone. Aluminium is softer and more prone to surface scratching than steel. It is not magnetic, which can be a limitation for fixturing. Thicker sections (above 6mm) are slower and more expensive to laser cut.

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