GlossaryKind of term: Manufacturing termAluminium
What is aluminium?
Aluminium is a light non-ferrous metal; in machining you work with alloys in a defined temper, such as EN AW-6082 T6 or EN AW-7075 T651.
Aluminium is a light non-ferrous metal with a density of about a third of steel. In machining it is almost invariably an alloy: wrought alloys such as EN AW-6082, 6061, 5083, 2011 and 7075 as block, plate and bar, alongside cast tooling plate and castings. Alloy and temper together set strength, machinability, corrosion behaviour, weldability and response to anodising. The word aluminium on its own is therefore not a material specification.
What does the standard say about aluminium?
The numerical designation and composition of wrought alloys are set in EN 573, the tempers in EN 515: O for annealed, H for strain hardened and T for heat treated, for example T6 for solution treated and artificially aged, and T651 for the same treatment with controlled stretching to reduce residual stress. Mechanical properties per product form are in product standards such as EN 485-2 for plate and EN 755-2 for extruded bar and profiles; the same alloy has different minimum values per form and thickness. US drawings use the same internationally registered four-digit numbers without the EN AW prefix, with ASTM product standards for properties and tolerances.
How does aluminium behave in the shop?
Most wrought alloys machine at high cutting speeds with little wear; high-silicon casting alloys are more abrasive, and 2011 is alloyed specifically for short chips. Machining time is therefore often short, so the material line can carry relatively more weight. Residual stress in thick material can cause distortion when one side is machined more than the other; a stress-relieved temper such as T651, cast plate, or reclamping between roughing and finishing limits that. Thin walls can chatter. Anodising results differ by alloy: copper-bearing alloys such as 2011 and 7075 give a less uniform layer than 6082, and because the layer partly grows outwards, fits must allow for the layer thickness.
What is aluminium often confused with?
Aluminium is not a material specification: 6082 T6 and 7075 T651 differ in strength, price, availability and machinability. And 6061 is not 6082: both are aluminium-magnesium-silicon alloys for similar uses, but with a different composition and, in Europe, different availability. Whether one may replace the other is the customer's decision.
Frequently asked questions
Which aluminium alloy is most common in milled work?
In Europe often EN AW-6082 T6, on US drawings often 6061 T6, both for frames, housings and plates. 7075 where strength counts, cast plate where the part must stay flat after machining, 5083 for welded or seawater service. The drawing should state alloy and temper.
What do T6 and T651 mean?
They are tempers under EN 515. T6 is solution treated and artificially aged. T651 is the same treatment with controlled stretching to reduce residual stress, which limits distortion during machining.
Why can an aluminium part still turn out expensive?
The cost is not only in the cutting. Distortion in a thick block, thin walls, a tight flatness or dimensionally controlled anodising can call for extra setups, inspection time or a subcontracted operation. How much that adds depends on shape, requirements and quantity.