Aluminum and its applications. Properties and applications of aluminum. The main alloying elements in aluminum alloys and their functions

federal agency by education of the Russian Federation

State Technological University

"Moscow Institute of Steel and Alloys"

Russian School Olympiad

"Innovative technologies and materials science"

II stage: Scientific and creative competition

Direction (profile):

"Material science and technology of new materials"

"Properties of aluminum and applications in industry and everyday life"

I've done the work:

Zaitsev Viktor Vladislavovich

Moscow, 2009

1. Introduction

4. The use of aluminum and its alloys in industry and everyday life

4.1 Aviation

4.2 Shipbuilding

4.3 Railway transport

4.4 Road transport

4.5 Construction

4.6 Oil and chemical industry

4.7 Aluminum cookware

5. Conclusion

5.1. Aluminum is the material of the future

6. List of used literature

1. Introduction

In my essay on the topic “Properties of aluminum and applications in industry and everyday life”, I would like to point out the peculiarity of this metal and its superiority over others. My entire text is proof that aluminum is the metal of the future and without it our further development will be difficult.

1.1 General definition of aluminum

Aluminum ( lat. Aluminum, from alumen - alum) - a chemical element III gr. periodic system, atomic number 13, atomic mass 26.98154. Silver-white metal, light, ductile, with high electrical conductivity, tm = 660 °C. Chemically active (covered with a protective oxide film in air). In terms of prevalence in nature, it ranks 3rd among elements and 1st among metals (8.8% of the mass of the earth's crust). In terms of electrical conductivity, aluminum is in 4th place, second only to silver (it is in first place), copper and gold, which, given the low cost of aluminum, is of great practical importance. There is twice as much aluminum as iron and 350 times as much as copper, zinc, chromium, tin and lead combined. Its density is only 2.7 * 10 3 kg/m 3 . Aluminum has a face-centered cube lattice and is stable at temperatures from -269 °C to the melting point (660 °C). The thermal conductivity is at 24°C 2.37 W×cm -1 ×K -1 . The electrical resistance of high purity aluminum (99.99%) at 20°C is 2.6548×10 -8 Ohm×m, or 65% of the electrical resistance of the international standard of annealed copper. The reflectivity of the polished surface is over 90%.

1.2 History of aluminum production

The documented discovery of aluminum occurred in 1825. The Danish physicist Hans Christian Oersted first obtained this metal when he isolated it by the action of potassium amalgam on anhydrous aluminum chloride (obtained by passing chlorine through a hot mixture of aluminum oxide and coal). Having driven away the mercury, Oersted obtained aluminum, however, contaminated with impurities. In 1827, the German chemist Friedrich Wöhler obtained aluminum in powder form by reducing potassium hexafluoroaluminate. Modern way aluminum production was discovered in 1886 by a young American explorer, Charles Martin Hall. (From 1855 to 1890, only 200 tons of aluminum were obtained, and over the next decade, 28,000 tons of this metal were obtained worldwide using the Hall method.) Aluminum with a purity of over 99.99% was first obtained by electrolysis in 1920. In 1925, Edwards published some information about the physical and mechanical properties of such aluminum. In 1938 Taylor, Willey, Smith, and Edwards published an article that gives some of the properties of 99.996% pure aluminum, also obtained in France by electrolysis. The first edition of the monograph on the properties of aluminum was published in 1967. Until recently, it was believed that aluminum, as a very active metal, cannot occur in nature in a free state, but in 1978. in the rocks of the Siberian platform, native aluminum was discovered - in the form of whiskers only 0.5 mm long (with a few micrometers thick threads). Native aluminum was also found in the lunar soil delivered to Earth from the regions of the Seas of Crises and Abundance. It is assumed that metallic aluminum can be formed by condensation from the gas. With a strong increase in temperature, aluminum halides decompose, passing into a state with a lower valency of the metal, for example, AlCl. When such a compound condenses with a decrease in temperature and the absence of oxygen, a disproportionation reaction occurs in the solid phase: some of the aluminum atoms are oxidized and go into the usual trivalent state, and some are reduced. Monovalent aluminum can be reduced only to the metal: 3AlCl > 2Al + AlCl 3 . This assumption is also supported by the filamentous shape of native aluminum crystals. Typically, crystals of this structure are formed due to rapid growth from the gas phase. Probably, microscopic aluminum nuggets in the lunar soil were formed in a similar way.

2. Classification of aluminum according to the degree of purity and its mechanical properties

In subsequent years, due to the relative ease of preparation and attractive properties, many works were published on the properties of aluminum. Pure aluminum has found wide application mainly in electronics - from electrolytic capacitors to the pinnacle of electronic engineering - microprocessors; in cryoelectronics, cryomagnetics. Newer methods for obtaining pure aluminum are the zone purification method, crystallization from amalgams (alloys of aluminum with mercury) and isolation from alkaline solutions. The degree of purity of aluminum is controlled by the value of electrical resistance at low temperatures. Currently, the following classification of aluminum according to the degree of purity is used:

Mechanical properties of aluminum at room temperature:

3. The main alloying elements in aluminum alloys and their functions

Pure aluminum is a rather soft metal - almost three times softer than copper, so even relatively thick aluminum plates and rods are easy to bend, but when aluminum forms alloys (there are a huge number of them), its hardness can increase tenfold. The most widely used:

Beryllium is added to reduce oxidation at elevated temperatures. Small additions of beryllium (0.01 - 0.05%) are used in aluminum casting alloys to improve fluidity in the production of parts for internal combustion engines (pistons and cylinder heads).

Boron is introduced to increase electrical conductivity and as a refining additive. Boron is introduced into aluminum alloys used in nuclear power(except for parts of reactors), because it absorbs neutrons, preventing the spread of radiation. Boron is introduced on average in the amount of 0.095 - 0.1%.

Bismuth. Low melting point metals such as bismuth, lead, tin, cadmium are added to aluminum alloys to improve machinability. These elements form soft fusible phases that contribute to chip breakage and cutter lubrication.

Gallium is added in the amount of 0.01 - 0.1% to the alloys from which the sacrificial anodes are further made.

Iron. In small quantities (>0.04%) it is introduced during the production of wires to increase strength and improve creep characteristics. Iron also reduces sticking to the walls of molds when casting into a chill mold.

Indium. The addition of 0.05 - 0.2% strengthens aluminum alloys during aging, especially at low copper content. Indium additives are used in aluminum-cadmium bearing alloys.

Approximately 0.3% cadmium is added to increase the strength and improve the corrosion properties of the alloys.

Calcium gives plasticity. With a calcium content of 5%, the alloy has the effect of superplasticity.

Silicon is the most used additive in foundry alloys. In the amount of 0.5 - 4% reduces the tendency to cracking. The combination of silicon and magnesium makes it possible to heat seal the alloy.

Magnesium. The addition of magnesium significantly increases strength without reducing ductility, improves weldability and increases the corrosion resistance of the alloy.

Copper strengthens alloys, maximum hardening is achieved with a copper content of 4 - 6%. Alloys with copper are used in the production of pistons for internal combustion engines, high-quality cast parts aircraft.

Tin improves machining.

Titanium. The main task of titanium in alloys is grain refinement in castings and ingots, which greatly increases the strength and uniformity of properties throughout the volume.

Aluminum is one of the most common and cheapest metals. It's hard to imagine without it modern life. No wonder aluminum is called the metal of the 20th century. It lends itself well to processing: forging, stamping, rolling, drawing, pressing. Pure aluminum is a fairly soft metal; it is used to make electrical wires, structural parts, foil for food products, kitchen utensils and "silver" paint. This beautiful and light metal is widely used in construction and aviation technology. Aluminum reflects light very well. Therefore, it is used for the manufacture of mirrors - by metal deposition in a vacuum.

Currently, aluminum and its alloys are used in almost all areas of modern technology. The most important consumers of aluminum and its alloys are the aviation and automotive industries, railway and water transport, mechanical engineering, the electrical and instrumentation industry, industrial and civil engineering, the chemical industry, and the production of consumer goods.

Most aluminum alloys have high corrosion resistance in the natural atmosphere, sea water, solutions of many salts and chemicals, and in most foods. Aluminum alloy structures are often used in sea water. Sea buoys, lifeboats, ships, barges have been built from aluminum alloys since 1930. At present, the length of aluminum alloy ship hulls reaches 61 m. There is experience in aluminum underground pipelines, aluminum alloys are highly resistant to soil corrosion. In 1951, a 2.9 km long pipeline was built in Alaska. After 30 years of operation, no leaks or serious damage due to corrosion have been found.

Aluminum is widely used in construction in the form of cladding panels, doors, window frames, electric cables. Aluminum alloys are not subject to severe corrosion for a long time in contact with concrete, mortar, plaster, especially if the structures are not frequently wet. With frequent wetting, if the surface of aluminum products has not been additionally treated, it can darken, up to blackening in industrial cities with a high content of oxidizing agents in the air. To avoid this, special alloys are produced to obtain shiny surfaces by brilliant anodizing - applying an oxide film to the metal surface. In this case, the surface can be given a variety of colors and shades. For example, alloys of aluminum with silicon allow you to get a range of shades, from gray to black. Aluminum alloys with chromium have a golden color.

Aluminum powders are also used in industry. They are used in the metallurgical industry: in aluminothermy, as alloying additives, for the manufacture of semi-finished products by pressing and sintering. This method produces very durable parts (gears, bushings, etc.). Powders are also used in chemistry to obtain aluminum compounds and as a catalyst (for example, in the production of ethylene and acetone). Given the high reactivity of aluminum, especially in the form of a powder, it is used in explosives and solid propellants for rockets, using its ability to quickly ignite.

Given the high resistance of aluminum to oxidation, the powder is used as a pigment in coatings for painting equipment, roofs, paper in printing, shiny surfaces of car panels. Also, steel and cast iron products are coated with a layer of aluminum to prevent their corrosion.

In terms of application, aluminum and its alloys are second only to iron (Fe) and its alloys. The widespread use of aluminum in various fields of technology and everyday life is associated with a combination of its physical, mechanical and chemical properties: low density, corrosion resistance in atmospheric air, high thermal and electrical conductivity, ductility and relatively high strength. Aluminum is easy to work with different ways- forging, stamping, rolling, etc. Pure aluminum is used for the manufacture of wire (the electrical conductivity of aluminum is 65.5% of the electrical conductivity of copper, but aluminum is more than three times lighter than copper, so aluminum often replaces copper in electrical engineering) and foil used as packaging material. The main part of the smelted aluminum is spent on obtaining various alloys. Protective and decorative coatings are easily applied to the surface of aluminum alloys.

The variety of properties of aluminum alloys is due to the introduction of various additives into aluminum, which form solid solutions or intermetallic compounds with it. The bulk of aluminum is used to produce light alloys - duralumin (94% - aluminum, 4% copper (Cu), 0.5% each magnesium (Mg), manganese (Mn), iron (Fe) and silicon (Si)), silumin (85-90% - aluminum, 10-14% silicon (Si), 0.1% sodium (Na)) and others. In metallurgy, aluminum is used not only as a base for alloys, but also as one of the widely used alloying additives in alloys based on copper (Cu), magnesium (Mg), iron (Fe), >nickel (Ni), etc.

Aluminum alloys are widely used in everyday life, in construction and architecture, in the automotive industry, in shipbuilding, aviation and space technology. In particular, the first artificial Earth satellite was made of aluminum alloy. An alloy of aluminum and zirconium (Zr) is widely used in nuclear reactor building. Aluminum is used in the manufacture of explosives. When handling aluminum in everyday life, you need to keep in mind that only neutral (by acidity) liquids (for example, boil water) can be heated and stored in aluminum dishes. If, for example, sour cabbage soup is boiled in aluminum cookware, then aluminum passes into food, and it acquires an unpleasant "metallic" taste. Since the oxide film is very easy to damage in everyday life, the use of aluminum cookware is still undesirable.

The use of aluminum and its alloys in all types of transport and, first of all, air transport made it possible to solve the problem of reducing its own ("dead") mass Vehicle and dramatically increase their effectiveness. Aircraft structures, engines, blocks, cylinder heads, crankcases, gearboxes are made from aluminum and its alloys. Aluminum and its alloys are used to finish railroad cars, ship hulls and chimneys, rescue boats, radar masts, ladders. Aluminum and its alloys are widely used in the electrical industry for the manufacture of cables, busbars, capacitors, rectifiers. alternating current. In instrumentation, aluminum and its alloys are used in the production of film and photographic equipment, radiotelephone equipment, and various instrumentation. Due to its high corrosion resistance and non-toxicity, aluminum is widely used in the manufacture of equipment for the production and storage of strong nitric acid, hydrogen peroxide, organic matter and food products. Aluminum foil, being stronger and cheaper than tin foil, completely replaced it as a food packaging material. Aluminum is increasingly used in the manufacture of containers for canning and storage of products. Agriculture, for the construction of granaries and other prefabricated structures. Being one of the most important strategic metals, aluminum, like its alloys, is widely used in the construction of aircraft, tanks, artillery installations, rockets, incendiaries, and for other purposes in military equipment.

High-purity aluminum is widely used in new areas of technology - nuclear power, semiconductor electronics, radar, as well as to protect metal surfaces from the action of various chemicals and atmospheric corrosion. The high reflectivity of such aluminum is used to make heating and lighting reflectors and mirrors from its reflective surfaces. In the metallurgical industry, aluminum is used as a reducing agent in the production of a number of metals (for example, chromium, calcium, manganese) by alumino-thermal methods, for steel deoxidation, and welding of steel parts.

Aluminum and its alloys are widely used in industrial and civil engineering for the manufacture of building frames, trusses, window frames, stairs, etc. In Canada, for example, aluminum consumption for these purposes is about 30% of total consumption, in the USA - more than 20%. In terms of production scale and importance in the economy, aluminum has firmly taken first place among other non-ferrous metals.

Physical properties of aluminum

Aluminum is a soft, light, silvery-white metal with high thermal and electrical conductivity. Melting point 660°C.

In terms of prevalence in the earth's crust, aluminum ranks 3rd after oxygen and silicon among all atoms and 1st among metals.

The advantages of aluminum and its alloys include its low density (2.7 g/cm3), relatively high strength characteristics, good thermal and electrical conductivity, manufacturability, and high corrosion resistance. The combination of these properties makes it possible to classify aluminum as one of the most important technical materials.

Aluminum and its alloys are divided according to the method of production into deformable, subjected to pressure treatment and foundry, used in the form of shaped casting; on the use of heat treatment - on thermally non-hardened and thermally hardened, as well as on alloying systems.

Receipt

Aluminum was first obtained by Hans Oersted in 1825. Modern Method The receipts were developed independently by the American Charles Hall and the Frenchman Paul Héroux. It consists in the dissolution of aluminum oxide Al2O3 in a melt of Na3AlF6 cryolite, followed by electrolysis using graphite electrodes. This method of obtaining requires large amounts of electricity, and therefore was in demand only in the 20th century.

Application

Aluminum is widely used as structural material. The main advantages of aluminum in this quality are lightness, ductility for stamping, corrosion resistance (in air, aluminum is instantly covered with a strong Al2O3 film, which prevents its further oxidation), high thermal conductivity, non-toxicity of its compounds. In particular, these properties have made aluminum extremely popular in the manufacture of cookware, aluminum foil v Food Industry and for packaging.

The main disadvantage of aluminum as a structural material is its low strength, so it is usually alloyed with a small amount of copper and magnesium (the alloy is called duralumin).

The electrical conductivity of aluminum is comparable to copper, while aluminum is cheaper. Therefore, it is widely used in electrical engineering for the manufacture of wires, their shielding, and even in microelectronics for the manufacture of conductors in chips. True, aluminum as an electrical material has an unpleasant property - because of the strong oxide film, it is difficult to solder it.

Due to the complex of properties, it is widely used in thermal equipment.

The introduction of aluminum alloys in construction reduces metal consumption, increases the durability and reliability of structures when they are used in extreme conditions (low temperature, earthquake, etc.).

Aluminum is widely used in various types transport. On the present stage development of aviation aluminum alloys are the main structural materials in the aircraft industry. Aluminum and alloys based on it are increasingly used in shipbuilding. Hulls, deck superstructures, communications and various kinds of ship equipment are made from aluminum alloys.

Research is underway to develop foamed aluminum as a particularly strong and lightweight material.

precious aluminum

Aluminum is one of the most popular and widely used metals today. From the very moment of its discovery in the middle of the 19th century, it was considered one of the most valuable thanks to its amazing qualities: white as silver, light in weight and not affected by environment. Its value was higher than the price of gold. Not surprisingly, aluminum was first used in the creation of jewelry and expensive decorative items.

In 1855, at the Universal Exhibition in Paris, aluminum was the main attraction. Aluminum items were placed in a showcase adjacent to French crown diamonds. Gradually, a certain fashion for aluminum was born. It was considered a noble, little-studied metal, used exclusively to create works of art.

Most often, aluminum was used by jewelers. With the help of a special surface treatment, jewelers achieved the lightest color of the metal, which is why it was often equated with silver. But compared to silver, aluminum had a softer luster, which made jewelers even more fond of it.

Because chemical and physical properties of aluminum at first they were poorly studied, jewelers themselves invented new techniques for processing it. Aluminum is technically easy to process, this soft metal allows you to create prints of any patterns, apply drawings and create the desired shape of the product. Aluminum was covered with gold, polished and brought to matte shades.

But over time, aluminum began to fall in price. If in 1854-1856 the cost of one kilogram of aluminum was 3 thousand old francs, then in the mid-1860s, about a hundred old francs were already given per kilogram of this metal. Subsequently, due to the low cost, aluminum fell out of fashion.

Currently, the very first aluminum products are very rare. Most of them did not survive the depreciation of the metal and were replaced by silver, gold and other precious metals and alloys. Recently, there has been renewed interest in aluminum among specialists. This metal was the subject of a separate exhibition organized in 2000 by the Carnegie Museum in Pittsburgh. Located in France Institute of Aluminum History, which in particular is engaged in the study of the first jewelry made from this metal.

In the Soviet Union, catering appliances, kettles, etc. were made from aluminum. And not only. The first Soviet satellite was made of aluminum alloy. Another consumer of aluminum is the electrical industry: wires of high-voltage transmission lines, windings of motors and transformers, cables, lamp bases, capacitors and many other products are made from it. In addition, aluminum powder is used in explosives and solid propellants for rockets, using its ability to quickly ignite: if aluminum was not covered with a thin oxide film, it could flare up in air.

The latest invention is aluminum foam, the so-called. "metal foam", which is predicted a great future.

The chemical element aluminum is light metal silver color. Aluminum is the most common metal in the earth's crust. Physical and Chemical properties aluminum allowed him to find wide application in modern industry and everyday life.

Chemical properties of aluminum

The chemical formula of aluminum is Al. Atomic number 13. Aluminum belongs to simple substances, since its molecule contains an atom of only one element. The outer energy level of an aluminum atom contains 3 electrons. These electrons are easily donated by the aluminum atom during chemical reactions. Therefore, aluminum has a high chemical activity and is able to displace metals from their oxides. But under normal conditions, it is quite resistant to chemical interaction, as it is covered with a strong oxide film.

Aluminum reacts with oxygen only at high temperatures. As a result of the reaction, alumina is formed. With sulfur, phosphorus, nitrogen, carbon, the interaction also occurs at high temperatures. But aluminum reacts with chlorine and bromine under normal conditions. It reacts with iodine when heated, but only if water acts as a catalyst. Aluminum does not react with hydrogen.

With metals, aluminum is able to form compounds called aluminides.

Aluminum, purified from the oxide film, reacts with water. The hydroxide, which is obtained as a result of this reaction, is a poorly soluble compound.

Aluminum readily reacts with dilute acids to form salts. But it reacts with concentrated acids only when heated, forming salts and acid reduction products.

Aluminum reacts easily with alkalis.

Physical properties of aluminum

Aluminum - durable metal, but at the same time, plastic, easily machined: stamping, polishing, drawing.

Aluminum is the lightest of the metals. It has a very high thermal conductivity. In terms of electrical conductivity, aluminum is practically not inferior to copper, but at the same time it is much lighter and cheaper.

Application of aluminum

For the first time aluminum metal was obtained by a Danish physicist Hans Christian Oersted in 1825. In those days, aluminum was considered a precious metal. Fashionistas loved to wear jewelry from it.

But the industrial method for producing aluminum was created much later - in 1855 by the French chemist Henri Etienne Saint-Clair Deville.

Aluminum alloys are used in almost all engineering industries. Modern aviation, space and automotive industries, shipbuilding cannot do without such alloys. The most famous alloys are duralumin, silumin, cast alloys. Perhaps the most popular of these alloys is duralumin.

When aluminum is processed by hot and cold processing, profiles, wire, pipes, tapes, sheets are obtained. Aluminum sheets or tape are widely used in modern construction. So, a special aluminum tape is used to seal the ends of various building panels in order to provide reliable protection against precipitation and dust ingress into the panel.

Since aluminum has a high electrical conductivity, it is used for the manufacture of electrical wires and electrical busbars.

Aluminum is not a precious metal. But some of its compounds are used in the jewelry industry. Probably, not everyone knows that ruby ​​and sapphire are single crystals of aluminum oxide, in which coloring oxides are added. The red color of a ruby ​​is given by chromium ions, and the blue color of sapphire is due to the content of iron and titanium ions. Pure crystalline alumina is called corundum.

In industrial conditions, artificial corundum, ruby ​​and sapphire are created.

Aluminum is also used in medicine. It is part of some drugs that have an adsorbing, enveloping and analgesic effect.

It is difficult to find a branch of modern industry that does not use aluminum and its compounds.

Aluminum has many valuable properties:

  • low density - about 2.7 g / cm 3,
  • high thermal conductivity and high electrical conductivity 13.8 107 Ohm / m,
  • good ductility and sufficient mechanical strength.

Aluminum forms alloys with many elements. In alloys, aluminum retains its properties. In the molten state, Al is fluid and fills molds well; in the solid state, it is well deformed and can be easily cut, soldered, and welded.

The affinity of aluminum for oxygen is very high.. During its oxidation, a large amount of heat is released (~ 1670000 J / mol). Finely ground aluminum ignites when heated and burns in air. Al combines with oxygen in the air and in atmospheric conditions. In this case, aluminum is covered with a thin (~ 0.0002 mm thick) dense film of aluminum oxide, which protects it from further oxidation; therefore Al is resistant to corrosion. The Al surface is well protected from oxidation by this film even in the molten state.

Of aluminum alloys, the most important are duralumin and silumin . The composition of duralumin, in addition to Al, includes 3.4-4% copper, 0.5% Mn and 0.5% Mg, not more than 0.8% Fe and 0.8% Si are allowed. Duralumin is well deformed and in its own way mechanical properties close to some grades of steel, although it is 2.7 times lighter than steel ( duralumin density 2.85 g / cm 3).

The mechanical properties of this alloy increase after heat treatment and cold deformation. Tensile strength increases from 147-216 MPa to 353-412 MPa, and Brinell hardness from 490-588 to 880-980 MPa. At the same time, the relative elongation of duralumin almost does not change and remains quite high (18-24%).

Silumins are cast alloys of aluminum with silicon. They have good casting qualities and mechanical properties.

Application

Aluminum and alloys are widely used in many industries, including aviation, transport, metallurgy, food industry, etc.. Aircraft bodies, engines, cylinder blocks, gearboxes, pumps and other parts in the aviation, automotive and tractor industries, storage vessels are made from aluminum and its alloys. chemical products. Aluminum is widely used in everyday life, food industry, nuclear power and electronics. Many parts of the artificial satellites of our planet and spaceships made of aluminum and its alloys.

Due to the high chemical affinity of aluminum for oxygen, it is used in ferrous metallurgy as a deoxidizer, as well as to obtain, using the so-called aluminothermic process, difficult-to-recover metals (calcium, lithium, etc.)..). By general production metal in the world, aluminum ranks second after iron.

 

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