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Characteristics of pure aluminum and aluminum alloy
Aluminum is currently the most widely used material for electronic heat sinks. The properties of aluminum are ideal for making aluminum heat sinks. Good thermal conductivity and low price.
The following describes the characteristics of pure aluminum and aluminum alloy used in the heat dissipation industry.
Pure aluminum: Density: Aluminum is a very light metal with a density of 2.71 g/cm3, which is about 1/3 of pure copper.
Conductive and thermal conductivity: aluminum has good thermal conductivity and electrical conductivity. When the cross section and length of aluminum are the same as copper, the electrical conductivity of aluminum is about 61% of copper. If the weight of aluminum and copper is the same (the length is equal), then Aluminum has a conductivity of 200% of copper.
Chemical properties: good resistance to atmospheric decay, because the surface is easy to form a dense aluminum oxide film, which can prevent further oxidation of internal metals. Aluminum does not react with concentrated nitric acid, organic acids and foods. Aluminum is a face-centered cubic structure. The industrial pure aluminum is extremely plastic (ψ=80%). It is easy to withstand various molding processes, but its strength is too low, σb is about 69Mpa, so pure aluminum can only be strengthened by cold deformation. Or alloying to increase its strength before it can be used as a structural material;
Aluminum is a non-magnetic, non-sparking material with good reflection properties. It can reflect both visible and ultraviolet light. The impurities in aluminum are silicon and iron. When the content of impurities is higher, the conductivity, corrosion resistance and plasticity are lower. ;
Second, aluminum alloy: If a certain amount of certain alloying elements are added to aluminum, and then subjected to cold working or heat treatment, certain characteristics can be greatly improved. The more commonly used alloying elements in aluminum are copper, magnesium, silicon, manganese and zinc. These elements may be added singly or sometimes in combination, and in addition to the above elements, a trace amount of titanium, boron, chromium, or the like may be added. According to the composition of the aluminum alloy and the characteristics of the production process, it can be divided into two types: cast aluminum alloy and deformed aluminum alloy.
Deformed aluminum alloy: This kind of aluminum alloy is usually processed by hot or cold pressure, that is, through rolling, extrusion and other processes, and is used for making plates, pipes, rods and various profiles. These alloys are required to be quite high. Plasticity, so the alloy content is less. For casting aluminum alloy, liquid metal is directly poured into the sand mold to make various shapes and complex parts. It is required to have good casting property for such alloys, that is, good fluidity, and when the alloy content is small, it is suitable for deforming aluminum alloy. When the alloy content is high, cast aluminum alloy.
The elastic modulus of aluminum alloy is small, which is only equivalent to 1/3 of steel. That is, under the same cross section, the same load is applied. The elastic deformation of aluminum alloy is three times that of steel, and the bearing capacity is not strong, but the seismic performance is good. The hardness range of the aluminum alloy (including the annealing and age hardening state) is 20 to 120 HB.
Harder aluminum alloys are softer than steel. The tensile strength limit of aluminum alloy is 90Mpa (pure aluminum) to 600Mpa (super hard aluminum).
Compared with steel, the gap is large. The melting point of aluminum alloy is low (generally around 600 °C, steel is around 1450 °C). The aluminum alloy has excellent plasticity at both normal temperature and high temperature, and can be formed into a structural part having an extremely complicated cross-sectional shape and a thin wall and high dimensional accuracy by extrusion. In addition to suitable mechanical properties, aluminum alloys also have excellent corrosion resistance, thermal conductivity and throwing properties.