WikiPedalia is not endorsed or affiliated with the Wikimedia Foundation.
Aluminum
A metal used for many bicycle parts. Aluminum is light and does not rust, though it will corrode if exposed to salt. By weight, it is not as strong as steel, but it weighs 1/3 what a similar volume of steel weighs. Aluminum is one of several materials that are quite suitable for making bicycle frames.
On virtually all good quality bicycles, aluminum is used for cranks, chainwheels, rims, handlebars, stems, brake parts and derailer parts.
Aluminum is not suitable for spokes, cables, or highly-stressed threaded fasteners in general.
Most English-speaking countries outside of North America stick an extra syllable into the word, and call it "aluminium".
See also the excellent article by Scott Nicol.
Different aluminum alloys and treatments are designated by a numerical code, as explained by Jeff Del Papa:
They indicate what other stuff is mixed in with the aluminum. Pure aluminum isn't all that strong. Add some silicon, magnesium, zinc, copper, and other things, and the result will be far stronger.
The first digit tells what "family" it belongs to:
1xxx Commercial aluminium (more than 99 per cent Al) 2xxx Copper 3xxx Manganese 4xxx Silicon 5xxx Magnesium 6xxx Magnesium and silicon 7xxx Zinc 8xxx Other elements The other 3 digits can be looked up in a table, to tell you how much of each they get, and how good the result is. They are assigned in order requested, they don't have any relationship to how much of each ingredient is used, or the properties of the result. (unlike steel alloys, whose numbers (1020, 4130, 4340) include the carbon content.)
If you see things like -T6, following the alloy series, those describe any heat treating the stuff got after it was made. Getting this done correctly is critical to the strength of the frame. For most aluminum frames, it is done after the frame is welded, as the heat from welding will change the metal (usually makes aluminum alloys softer) Heat treating typically involves heating an aluminum frams to near melting (900-1000F), it melts around 1100F, your oven self cleans at 800-850), holding it there for some amount of time (for thin tube, 1/2-2 hours or so) cooling suddenly (dunk in water), then a long bake (8 or more hours) at a lower temperature (like 350F).
The different alloys vary in tensile strength, corrosion resistance, welding compatibility, ductility, and machineability. The density of aluminum alloys doesn't vary much at all (under 5%) and the stiffness doesn't change.
Each alloy has good points and bad points. What counts as good or bad depends on what you are going to do with it. Some very strong alloys can't be welded, so they make bad frames, and great chainrings. Another alloy might give up some absolute strength, but gain some resistance to cracking. One may cost more, but the heat treating process is cheaper. If you are bolting or bonding things together, you can mix alloys. If you are going to weld, all the welded parts have to use an identical filler material and heat treating schedule. (so you can't mix 6061, and 7005 in the same welded structure)
It's the designer's job to chose correctly among the various tradeoffs. If the designer chose well, even a not particularly exotic material can do the job just fine. Pick wrong, and even exotic super-alloys will break.
