Aluminum 6061

The default structural aluminum, and the answer to "6061 or 7075" for almost everything that has to be welded: 6061 welds cleanly, extrudes into complicated profiles, and resists corrosion well. 7075 is nearly twice as strong but effectively unweldable and will corrode in salt air, so it goes where parts are bolted or riveted. The 125-310 MPa span is the temper: 6061-O annealed is soft enough to bend by hand, 6061-T6 is not, and welding locally returns T6 back towards O.

Properties

Density

2,700 kg/m³ — 2.70 g/cm³

Melting range

582–652 °C

Tensile strength

125–310 MPa

Young's modulus

68.9 GPa

Thermal conductivity

167 W/(m·K)

Thermal expansion

23.6 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Extruded profile and T-slot framing
• Bicycle frames and scaffolding
• Machined brackets and enclosures
• Boat hulls and superstructure

How it compares

Does it rust?

No — aluminium cannot rust, because rust is specifically iron oxide and there is no iron in it. It does oxidise, immediately and constantly, but aluminium oxide is hard, tightly bonded and only a few nanometres thick, and it protects the metal beneath rather than flaking away. It does corrode galvanically when in contact with a dissimilar metal in a damp environment, which is a different mechanism.

Is it magnetic?

Aluminum 6061 is not ferromagnetic. It is often assumed to be because it is a metal, but most metals are not — only iron, nickel, cobalt and a few alloys are attracted to an ordinary magnet.