What is Aluminium?
Aluminium is a silvery-white, soft, ductile and non-magnetic metal. It is the third most abundant element after oxygen and silicon and the most abundant metal in the Earth’s crust.
It is often used for its extremely low density and its ability to resist corrosion.
Before Aluminium was mass produced, it was considered as rare and valuable as gold. At this time, it was extremely rare to find in its metal form. Napoléon III was known to have a set of Aluminium cutlery and wealthy women wore jewellery crafted from the metal. A patent saw mass production begin in 1886. Since then, Aluminium manufacturing hasn’t changed much, but the technology used to refine it has improved. Therefore, the quality of the Aluminium produced continues to increase.
The process required to achieve Aluminium starts with Bauxite, which is ground and mixed with lime and Caustic Soda, then heated in high-pressure containers. The Aluminium oxide is dissolved by the Caustic Soda, precipitated out of the solution, washed and heated to eliminate water. The resulting Alumina is a white powder resembling sugar. Refining four pounds of Bauxite results in two pounds of Alumina.
The Alumina is further refined by smelting. This draws Oxygen atoms out of the Alumina, leaving molten Aluminium at the bottom of the pot. The refined Aluminium is then siphoned out and put in a holding furnace, from which it can be cast into an ingot and sent to be formed into tubes, wires, sheet-discs, foams, foil or honeycombs.
The electrolytic process, however, is still far more expensive than recycling, which requires only a fraction of the energy. This is one of the main reasons Aluminium recycling is so useful and important.
Aluminium is a popular material for its unique combination of properties. At a third the weight of stainless steel, it is a lightweight metal with a higher strength-to-weight ratio. It is also an easy metal to work with due to to its relative softness, corrosion resistance and recyclability. It can go through the same fabrication techniques as any other commonly used metals, but certain methods work better than others.
Fabrication may include:
Extrusion puts the least stress on Aluminium as it forces the Aluminium through or around a die, shaping the metal to its size and shape. Extrusions can be done either hot (where the metal is heated) or cold (where the metal is room temperature).
Drawing pulls metal through a tapered die to stretch it, often into wire and products like cans, thanks to its inherent ductility.
Forming includes bending, stamping, and rolling, working with the material’s flexibility and softness.
Castings are made when liquid metal is poured into a mold or die.
Forging occurs when metal is beaten or compressed into shape usually for applications that require durability (such as for stress bearing parts).
Machining is a subtractive cutting process that sculpts by removing metal.
Waterjet cutting uses high pressure spraying of water with abrasives, but no heat. In this way it avoids altering Aluminium’s properties the way laser cutting could. However, it can still also be cut by saw blade, laser, or plasma cutting.
Does Aluminium conduct electricity?
It can conduct electricity, but not as well as more expensive alternatives such as Copper. Whilst an Aluminium conductor is only about 61% as conductive as the same sized Copper conductor, it is also three times lighter in weight which makes it much easier to handle. For this reason,it is usually applied in large size cables such as transmission lines.
Two properties of Aluminium that make it a useful conduct for electricity are that it does not spark and it does not rust. Because it does not create sparks when struck, it can be used safely near materials that are flammable or explosive. Its resistance to corrosion makes this material an ideal metal to use outdoors.
Uses of Aluminium
Aluminium’s properties make it ideal for uses that vary widely across industrial, commercial and consumer applications. In aerospace designers and engineers take advantage of its weight-to-strength ratio and corrosion resistance for the fabrication of wings, fuselages, and other parts. Its non-toxicity has made it a popular choice for food packaging, including cans and foil, which rely on Aluminium’s easy workability, softness, and durability.
Automotive applications use Aluminium to absorb crash forces, as well as to make car bodies and components lighter and therefore more fuel efficient. In construction, the material acts as both a decorative and structural material due to its energy efficiency and sustainable capabilities.
As mentioned above Aluminium is also used in electronics and electrical applications such as power grids as well as in some consumer electronics like refrigerators and laptops that take advantage of its thermal abilities, light weight, and structural strength.
Aluminium is, of course, not without its design applications. In fact, photographic records kept at the Institute for the History of Aluminium bear witness to the abundance and variety of the different Aluminium works presented at the 1937 International Exhibition, where the material occupied a place of honour in a pavilion that was specially reserved for it, found throughout the exhibition in the form of wall coverings, decorative motifs and furnishings. Applied as paint or in thin leaves as decoration. Since then Aluminium is a material of choice for artists and designers, chosen for its reflective properties and its easy-to-work malleability; simple, stark lines resulted from the bending, folding and curving of bars and sheets. The imperfect finish due to the softness of the metal gave the objects the rather crude look, typical of this first period in the decorative use of Aluminium. Its reflective and non-combustive properties have also carved out place for it in lighting.
Physical properties of Aluminium
One important characteristic of Aluminium is that it preserves its properties after processing, which means Aluminium products can be recycled into new products. This helps preserve the colossal amount of energy that has to be used to produce primary Aluminium.
The material offers a rare combination of valuable properties. It is one of the lightest metals in the world: it’s almost three times lighter than iron, but it’s also very strong, extremely flexible and corrosion resistant because its surface is always covered in an extremely thin and yet very strong layer of oxide film. This makes it particularly useful for protection and conservation. It doesn’t magnetise, it’s a great electricity conductor and forms alloys with practically all other metals. It can also be used for decorative surfaces, with mat, bright and structured variances.