Since the discovery of aluminum in 1825 by Danish scientist Oenrsted (HC.Oenrsted), it has been 187 years of history. If it is calculated from the advent of the molten salt electrolysis method (Hall-Heroult method) for industrial aluminum extraction in 1886, it has been 126 years. For more than 100 years, aluminum and its alloys have been widely used, mainly in aerospace, transportation, architectural decoration, packaging containers, machinery and electrical appliances, electronic communications, petrochemical, energy and power, sports and health and other industries, becoming an important basic material for national economic development. Aluminum production ranks first among non-ferrous metals, second only to steel production. The reason why aluminum is widely used, in addition to having rich reserves and easier smelting, more importantly, aluminum has a series of excellent characteristics, in general, aluminum has the following characteristics:
(1) Low density. The density of pure aluminum is close to 2700kg/m, which is about 35% of the density of iron.
(2) Can be strengthened. Although the strength of pure aluminum is not high, it can be more than doubled by cold processing, and it can be alloyed by adding magnesium, zinc, copper, manganese, silicon, lithium, scandium, chromium, zirconium and other elements, and then further strengthened by heat treatment, and its specific strength can be comparable to high-quality alloy steel.
(3) Easy to process. Aluminum can be cast by any casting method. Aluminum plasticity is good, can be rolled into sheet and foil; Drawn into pipes and wires; Extruded into various complex profiles; Machining such as turning, milling, boring and planing can be performed at maximum speed on most machine tools.
(4) Corrosion resistance. The surface of aluminum and its alloys is easily formed into a dense and firm AI2O3 protective film. This protective film can only be destroyed under the intense action of halogen ions or base ions. Therefore, aluminum has a good resistance to atmospheric (including industrial atmosphere and Marine atmosphere) corrosion. Can resist the corrosion of most acids and organic matter, using corrosion inhibitors. Resistant to weak alkali corrosion; The anti-ton property of aluminum alloy can be improved by taking corresponding protective measures.
(5) No low temperature brittleness. Aluminum below 0 ° C, with the reduction of temperature, strength and plasticity will not only not reduce, but will increase.
(6) Good electrical and thermal conductivity. Aluminum's electrical and thermal conductivity is second only to silver, copper and gold. At room temperature, the equal volume conductivity of electrical aluminum can reach 62%IACS, if calculated by unit mass conductivity, its conductivity is twice that of copper.
(7) Strong reflection. The reflectivity of the polished surface of aluminum to white light is more than 80%, and the higher the purity, the higher the reflectivity. At the same time, aluminum has good reflection performance on infrared, ultraviolet, electromagnetic wave, thermal radiation and so on.
(8) Non-magnetic, impact does not spark. This is valuable for some special purposes. For example, it is used as instrument materials, shielding materials for electrical equipment, and equipment for flammable and explosive production.
(9) Sound absorption. It is good for interior decoration, and can also be prepared into damping and damping alloy
(10) Nuclear radiation resistance. For high-energy neutrons, aluminum has the same neutron absorption cross section as other metals, and for neutrons in the low energy range, its absorption cross section is small, second only to beryllium magnesium, zirconium and other metals. The biggest advantage of aluminum nuclear radiation resistance is that the induced radiation energy generated by irradiation decays quickly.
(11) Beautiful. Aluminum and its alloy due to strong reflection ability, the surface is silver-white luster after machining can reach a high finish and brightness. If it is anodized and colored, it can not only improve the corrosion resistance, but also obtain colorful and dazzling products. Aluminum can also be electroplated and coated with ceramics, and is an excellent substrate for the production of paint materials.