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

Federal Agency for Education of the Russian Federation

State Technological University

"Moscow Institute of Steel and Alloys"

Russian Olympiad for schoolchildren

"Innovative technologies and materials science"

II-nd stage: Scientific and creative competition

Direction (profile):

"Materials Science and Technologies of New Materials "

"Aluminum properties and applications in industry and everyday life"

I've done the work:

Zaitsev Victor 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 Rail 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 "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. All my text is proof that the aluminum 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) - chemical element III gr. periodic system, atomic number 13, atomic mass 26.98154. Silver-white metal, light, ductile, with high electrical conductivity, tm \u003d 660 ° C. Chemically active (covered with a protective oxide film in air). In terms of prevalence in nature, it takes the 3rd place 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 the first place), copper and gold, which, given the cheapness of aluminum, is of great practical importance. Aluminum is twice as much 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, is stable at temperatures from - 269 ° С to the melting point (660 ° С). Thermal conductivity at 24 ° C is 2.37 W × cm -1 × K -1. The electrical resistance of high-purity aluminum (99.99%) at 20 ° С 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. For the first time this metal was obtained by the Danish physicist Hans Christian Oersted, 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 with coal). After distilling off the mercury, Oersted obtained aluminum, however, contaminated with impurities. In 1827 the German chemist Friedrich Wöhler obtained aluminum in powder form by reducing hexafluoroaluminate with potassium. The modern method of producing aluminum was discovered in 1886 by the young American researcher Charles Martin Hall. (From 1855 to 1890, only 200 tons of aluminum were obtained, and over the next decade, according to the Hall method, 28,000 tons of this metal were obtained worldwide) Aluminum with a purity of over 99.99% was first obtained by electrolysis in 1920. In 1925, Edwards published some information on the physical and mechanical properties of such aluminum. In 1938. Taylor, Willey, Smith and Edwards published an article that lists 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 found in the form of whiskers only 0.5 mm long (with a filament thickness of several micrometers). Native aluminum was also found in the lunar soil brought to Earth from the regions of the Seas of Crises and Abundance. It is believed that metallic aluminum can be formed by condensation from gas. With a strong increase in temperature, aluminum halides decompose, passing into a state with the lowest metal valence, for example, AlCl. When, with a decrease in temperature and the absence of oxygen, such a compound condenses, a disproportionation reaction occurs in the solid phase: some of the aluminum atoms are oxidized and pass into the usual trivalent state, and some are reduced. Univalent aluminum can only be reduced to metal: 3AlCl\u003e 2Al + AlCl 3. This assumption is supported by the filamentary shape of the crystals of native aluminum. Crystals of this structure are usually formed due to rapid growth from the gas phase. Probably, microscopic nuggets of aluminum in the lunar soil were formed in a similar way.

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

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

Mechanical properties of aluminum at room temperature:

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

Pure aluminum is a fairly 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 tens of times. 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 added to aluminum alloys used in nuclear power (except for reactor parts), 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, low-melting phases, which contribute to chip brittleness and tool lubrication.

Gallium is added in an amount of 0.01 - 0.1% to alloys, from which consumable anodes are further made.

Iron. In small quantities (»0.04%) it is introduced in the manufacture of wires to increase strength and improve creep characteristics. Iron also reduces adhesion to the walls of molds when casting in a chill mold.

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

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

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

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

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

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

Tin improves cutting performance.

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

Aluminum is one of the most common and cheapest metals. It is difficult to imagine modern life without it. 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, food foil, kitchen utensils and "silver" paint. This beautiful and lightweight metal is widely used in construction and aircraft engineering. Aluminum reflects light very well. Therefore, it is used for the manufacture of mirrors - by spraying metal 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 industry and instrument making, industrial and civil construction, the chemical industry, and the production of consumer goods.

Most aluminum alloys are highly resistant to corrosion in the natural atmosphere, sea water, solutions of many salts and chemicals, and in most food products. Aluminum alloy structures are often used in seawater. Marine buoys, lifeboats, ships, barges have been built from aluminum alloys since 1930. At present, the length of hulls of ships made of aluminum alloys reaches 61 m. There is experience with 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, not a single leak or serious corrosion damage has been found.

Aluminum is widely used in construction in the form of cladding panels, doors, window frames, and electrical cables. Aluminum alloys are not subject to strong corrosion for a long time in contact with concrete, mortar, plaster, especially if the structures are not exposed to frequent wetting. 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 oxidants in the air. To avoid this, special alloys are produced for obtaining shiny surfaces by shiny 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 provide a range of shades from gray to black. Aluminum alloys with chrome have a gold 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 is used to obtain very durable parts (gears, bushings, etc.). Powders are also used in chemistry to produce 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 property to quickly ignite.

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

In terms of the scale of application, aluminum and its alloys take the second place after iron (Fe) and its alloys. The widespread use of aluminum in various fields of technology and everyday life is associated with the combination of its physical, mechanical and chemical properties: low density, corrosion resistance in atmospheric air, high heat and electrical conductivity, plasticity and relatively high strength. Aluminum is easily processed in various ways - forging, stamping, rolling, etc. Pure aluminum is used to make 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 on 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 obtain 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)), etc. 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),\u003e 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 from an aluminum alloy. Alloy of aluminum and zirconium (Zr) - widely used in nuclear reactor building. Aluminum is used in the production of explosives. When handling aluminum at home, keep in mind that only neutral (in terms of acidity) liquids can be heated and stored in aluminum containers (for example, boil water). If, for example, sour cabbage soup is cooked in an aluminum dish, then the aluminum goes into food, and it acquires an unpleasant "metallic" taste. Since it is very easy to damage the oxide film 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 the own ("dead") mass of vehicles and dramatically increase the efficiency of their use. Aircraft structures, motors, blocks, cylinder heads, crankcases, gearboxes are made of aluminum and its alloys. Railway carriages are trimmed with aluminum and its alloys, hulls and chimneys of ships, rescue boats, radar masts, ladders are manufactured. Aluminum and its alloys are widely used in the electrical industry for the manufacture of cables, busbars, capacitors, and AC rectifiers. In instrument making, aluminum and its alloys are used in the production of cinema and photographic equipment, radiotelephone equipment, and various control and measuring instruments. 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 substances and food products. Aluminum foil, being stronger and cheaper than tin, has completely replaced it as a packaging material for food. Aluminum is more and more widely used in the manufacture of containers for canning and snoring of agricultural products, for the construction of granaries and other pre-fabricated structures. As one of the most important strategic metals, aluminum, like its alloys, is widely used in the construction of aircraft, tanks, artillery installations, missiles, incendiary substances, as well as 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 various chemicals and atmospheric corrosion. The high reflectivity of such aluminum is used to make heating and lighting reflectors and mirrors from it 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 aluminum-thermal methods, for deoxidizing steel, welding steel parts.

Aluminum and its alloys are widely used in industrial and civil construction 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, lightweight, 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 place 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 wrought, subjected to pressure treatment and foundry, used in the form of shaped casting; for the use of heat treatment - for thermally not hardened and thermally hardened, as well as for alloying systems.

Receiving

For the first time aluminum was obtained by Hans Oersted in 1825. The modern method of obtaining was developed independently of each other by the American Charles Hall and the Frenchman Paul Héroux. It consists in dissolving aluminum oxide Al2O3 in a cryolite melt Na3AlF6, followed by electrolysis using graphite electrodes. This method of obtaining requires large amounts of electricity, and therefore was in demand only in the XX century.

Application

Aluminum is widely used as construction material... The main advantages of aluminum in this capacity are lightness, pliability to stamping, corrosion resistance (in air, aluminum is instantly covered with a strong Al2O3 film, which prevents its further oxidation), high thermal conductivity, and non-toxicity of its compounds. In particular, these properties have made aluminum extremely popular in the manufacture of kitchenware, aluminum foil in the 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 that of 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 - it is difficult to solder it due to its strong oxide film.

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

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

Aluminum is widely used in various types of transport. At the present stage of aviation development, aluminum alloys are the main structural materials in aircraft construction. Aluminum and alloys based on it are increasingly used in shipbuilding. Aluminum alloys are used to manufacture ship hulls, deck superstructures, communications and various types of ship equipment.

Research is underway to develop foam aluminum as an extra strong and lightweight material.

Precious aluminum

Today aluminum is one of the most popular and widely used metals. Since its discovery in the middle of the 19th century, it has been considered one of the most valuable for its amazing qualities: white as silver, light in weight and not affected by the environment. Its value was higher than the price of gold. Not surprisingly, aluminum is primarily used in jewelry and expensive decorative items.

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

The most commonly 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 in comparison with silver, aluminum possessed a softer luster, which caused an even greater love for it by jewelers.

As chemical and physical properties of aluminum at first were poorly studied, jewelers themselves invented new techniques for its processing. Aluminum is technically easy to process, this soft metal allows you to create prints of any patterns, apply patterns and create the desired shape of the product. The aluminum was plated with gold, polished and finished 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 given per kilogram of this metal. Subsequently, due to the low cost, aluminum went out of fashion.

Nowadays, the very first aluminum products are very rare. Most of them did not survive the depreciation of the metal and was replaced by silver, gold and other precious metals and alloys. Recently, there has been a 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 for the History of Aluminum, which in particular is engaged in the study of the first jewelry made of this metal.

In the Soviet Union, all-food 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 from 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 fuel for rockets, using its ability to quickly ignite: if aluminum were not covered by the thinnest oxide film, it could flash in air.

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

The chemical element aluminum is a light silver metal. Aluminum is the most common metal in the earth's crust. The physical and chemical properties of aluminum allowed it to be widely used in modern industry and everyday life.

Chemical properties of aluminum

Chemical formula of aluminum Al. Atomic number 13. Aluminum refers to simple substances, since its molecule contains an atom of only one element. The external 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 interacts with oxygen only at high temperatures. As a result of the reaction, aluminum oxide is formed. With sulfur, phosphorus, nitrogen, carbon, interaction also occurs at high temperature. But with chlorine and bromine, aluminum reacts under ordinary conditions. It reacts with iodine when heated, but only if water acts as a catalyst. Aluminum does not interact with hydrogen.

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

Aluminum, purified from an oxide film, reacts with water. The hydroxide resulting from this reaction is a poorly soluble compound.

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

Aluminum readily reacts with alkalis.

Physical properties of aluminum

Aluminum is a strong metal, but at the same time it is plastic, it can be easily machined: stamping, polishing, stretching.

Aluminum is the lightest of all metals. Has a very high thermal conductivity. In terms of electrical conductivity, aluminum is almost as good as copper, but at the same time it is much lighter and cheaper.

Application of aluminum

The first metal aluminum was obtained by a Danish physicist Hans Christian Oersted in 1825... And in those days, aluminum was considered a precious metal. Fashionistas loved to wear jewelry from him.

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. The modern aviation, space and automobile industries, and shipbuilding cannot do without such alloys. The most famous alloys are duralumin, silumin, and casting alloys. Perhaps the most demanded of these alloys is duralumin.

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

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

Aluminum is not a precious metal. But some of its compounds are used in the jewelry industry. Probably not everyone knows that ruby \u200b\u200band sapphire are single crystals of aluminum oxide, which have added coloring oxides. The red color of ruby \u200b\u200bis given by chromium ions, and the blue color of sapphire is from the content of iron and titanium ions. Pure crystalline alumina is called corundum.

In an industrial environment, artificial corundum, ruby \u200b\u200band sapphire are created.

Aluminum is also used in medicine. It is part of some drugs that have an adsorbent, 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 of 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 can fill molds well; in the solid state, it deforms well and is easy to cut, solder and weld.

The affinity of aluminum for oxygen is very high... During its oxidation, a large amount of heat is released (~ 1670000 J / mol). Finely crushed aluminum when: heated, ignites and burns in air. Al combines with atmospheric oxygen. 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 corrosion resistant. The Al surface is well protected from oxidation by this film and in the molten state.

Of aluminum alloys, the most important duralumin and silumins . The composition of duralumin, in addition to Al, includes 3.4-4% copper, 0.5% Mn and 0.5% Mg, no more than 0.8% Fe and 0.8% Si are allowed... Duralumin is well deformed and, by its mechanical properties, is close to some grades of steel, although it is 2.7 times lighter than steel ( density of duralumin 2.85 g / cm 3).

The mechanical properties of this alloy increase after heat treatment and cold deformation. The tensile strength increases from 147-216 MPa to 353 - 412 MPa, and the Brinell hardness increases from 490-588 to 880-980 MPa. Moreover, the relative elongation of duralumin remains almost unchanged and remains quite high (18-24%).

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

Application

Aluminum and alloys are widely used in many industries, including aviation, transport, metallurgy, food industry, etc.... Aluminum and its alloys are used to produce airplane bodies, motors, cylinder blocks, gearboxes, pumps and other parts in the aviation, automobile and tractor industries, and vessels for storing chemical products. Aluminum is widely used in everyday life, food industry, in nuclear energy and electronics. Many parts of the artificial satellites of our planet and spacecraft are made of aluminum and its alloys.

Due to the large chemical affinity of aluminum to oxygen, it is used in the iron and steel industry as a deoxidizer, and also to obtain difficult to recover metals (calcium, lithium, etc., when using the so-called aluminothermic process)..). Aluminum is the second largest metal producer in the world after iron.

 

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