In 1827, German chemist Weiler discovered aluminum. The content of aluminum on the earth is vibrant. It ranks third in the earth’s crust, second only to oxygen and silicon. It is one of the most abundant metal elements, almost twice that of iron and nearly a thousand times that of copper. However, the chemical properties of aluminum in the Aluminium Sheet are very active, and it is tough to obtain metallic aluminum from mineral smelting. People used potassium metal to replace anhydrous aluminum chloride at that time, but it was necessary to collect enough metal aluminum powder to melt and cast into ingots. The whole process is more complicated. Therefore, in the 19th century, aluminum was a rare metal, and the aluminum particles that people first obtained were like treasures. Aluminum was far rarer than gold and silver at the time.
Legend has it that the knife and fork of Napoleon III were made of aluminum. At the banquet, he provided most guests with gold tableware and only let a few guests use aluminum tableware to leave a more profound impression on the guests who use aluminum tableware. In 1885, the top hat on the Washington Monument built in Washington, DC, the capital of the United States, was also made of metal aluminum.
In 1807, the British David separated the metal hidden in alum. Potassium and sodium were found through electrolysis, but the alumina could not be decomposed. The Swedish chemist Bezenius did a similar experiment, but it failed. However, scientists gave this vague metal a name. Becenius was initially called bauxite. British chemist David named it aluminum in 1809, which is now aluminum. Like fluorine, pure aluminum already has its name before it is extracted.
Aluminum is a light metal with a density of 2.71g/cm, about 1/3 of pure copper.
①. Electrical conductivity and thermal conductivity: Aluminum has good thermal conductivity and electrical conductivity. When the section and length of aluminum are the same as copper, the conductivity of aluminum is about 61% of copper. If aluminum and copper have the same weight but different cross-sections (equal length), the conductivity of aluminum is nearly 200% of copper.
②. Chemical properties: good resistance to atmospheric decay because a thick aluminum oxide film is easy to form on the surface, preventing further oxidation of the internal metal. Aluminum does not react with concentrated nitric acid, organic acids, and food. Aluminum has a face-centered cubic structure. Industrial pure aluminum has extremely high plasticity (=80%) and is easy to withstand various forming processes, but its strength is too low, σb is about 69Mpa, so pure aluminum can only be strengthened or alloyed by cold deformation Ways to increase the power can be used as a structural material;
Aluminum is a non-magnetic and non-sparking material with good reflection performance, which can reflect both visible light and ultraviolet; the impurities in aluminum are silicon and iron. The higher the impurity content, the lower the conductivity, corrosion resistance, and plasticity;
Some characteristics can be significantly improved after cold working or heat treatment if an appropriate amount of alloying elements are added to aluminum. Commonly used alloying elements in aluminum are copper, magnesium, silicon, manganese, and zinc, sometimes added separately or in combination. In addition to the above aspects, trace amounts of titanium, boron, chromium, etc., are sometimes added.
According to the composition and production process characteristics of aluminum alloy, it can be divided into cast aluminum alloy Aluminium Sheet and wrought aluminum alloy Aluminium Sheet.
①. Wrought aluminum alloy is usually processed by hot or cold pressure, rolling and extruding into plates, pipes, bars, and various profiles. This kind of alloy requires high plasticity, so the alloy content is low.
②. Casting aluminum alloy is to directly pour liquid metal into sand molds to make various parts with complex shapes. This alloy requires good castability, that is, good fluidity. When the alloy content is low, it is suitable for deformed aluminum alloy. When the alloy content is high, it should be made into cast aluminum alloy. The elastic deformation of aluminum alloy is small, only equivalent to 1/3 of steel; the same load is loaded on the same section. The elastic deformation of aluminum alloy is three times that of steel; the bearing capacity is not strong, but the seismic performance is good.
The hardness range of aluminum alloy (including annealing and age hardening) is 20~120HB. Rugged aluminum alloy is softer than steel. The tensile strength limit of aluminum alloy is 90Mpa (pure aluminum) to 600Mpa (super duralumin), which is far behind steel. Aluminum alloy has a low melting point (usually around 600°C, and steel around 1450°C). Aluminum alloy has excellent plasticity at room temperature and high temperature. It can be made into structural parts with highly complex cross-sectional shapes, thin walls, and high dimensional accuracy by extrusion. In addition to suitable mechanical properties, the aluminum alloy also has excellent corrosion resistance, thermal conductivity, and polishing properties.