The most important properties that make aluminum and its alloys the most economical and attractive for a wide variety of uses are:
- Appearance
- Light weight
- Corrosion resistance
- Physical properties
- Mechanical properties
- Formability
- Recyclability
- Light weight
Aluminum has a density of about one-third (2.7g/cm3) that of steel (7.83g/cm3), copper (8.93 g/cm3) and brass (8.53 g/cm3). A one-cubic-meter component of aluminum weighs 2.7 tonnes, while a similar steel component weighs 7.8 tonnes.
Aluminum, with its excellent combination of strength and lightness, is reducing the weight of planes and cars, buses, trucks, trains and boats, and thus decreasing energy consumption and pollution from transportation. Not surprisingly, the use of aluminum in trains, railcars, underground carriages, buses and boats, particularly for bodywork and hulls, is rapidly increasing.
Corrosion resistance
Aluminum resists the progressive oxidization that causes steel to rust. The exposed surface of aluminum combines with oxygen to form an inert aluminum oxide film, which blocks further oxidation. Unlike iron rust, the aluminum oxide film does not flake off to expose a fresh surface to further oxidation. Scratch through aluminum’s protective layer, and it instantly reseals itself. The thin oxide layer itself clings tightly to the metal and is colorless and transparent – invisible to the naked eye.
Physical properties
Aluminum surfaces can be highly reflective. Radiant energy, visible light, radiant heat and electromagnetic waves are efficiently reflected, while anodized and dark anodized surfaces can be reflective or absorbent. This is why aluminum is often selected for a variety of decorative and functional uses, for example, in building facades.
Aluminum displays excellent electrical and thermal conductivity, non-ferromagnetic, non-pyrophoric, non-toxic and has an attractive appearance in its natural finish. Aluminum is unrivalled as a packaging material for food and beverages, as well as pharmaceutical products.
Aluminum foil, even when rolled to just 0.007 mm in thickness, is still completely impermeable and lets neither light, aroma nor taste in or out. Because the metal itself is non-toxic, it releases no aroma or taste substances. Hence, aluminum is unrivalled as a packaging material for food and beverages, as well as pharmaceutical products.
Mechanical properties
Formability is among the more important characteristics of aluminum and many of its alloys. The strength levels of certain aluminum alloys are similar to structural steels. While aluminum has a similar specific modulus of elasticity as steel, the absolute modulus of elasticity is about one-third that of steel. In structural engineering this means higher deformations which can, however, be straightened out by optimized advanced design of the cross section. While such optimization generally allows a weight reduction vs. steel, the optimized cross-section size may be bigger than steel. Unlike steel, many aluminum alloys can be extruded, giving designers a wider range of possible cross-sections.
The machinability of most aluminum alloys is excellent. Aluminum can be joined by a wide variety of methods, including fusion and resistant welding, brazing, soldering, adhesive bonding, and mechanical methods such as riveting and bolting.
