Examples of the use of aluminum. The use of aluminum and its alloys

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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 used in large volumes in construction in the form of cladding panels, doors, window frames, electrical 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 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 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 (in 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 primarily in air, made it possible to solve the problem of reducing the dead weight of vehicles and dramatically increasing the efficiency of their use. 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, and AC rectifiers. In instrumentation, aluminum and its alloys are used in the production of cinema 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 substances and food products. Aluminum foil, being stronger and cheaper than tin foil, completely replaced it as a food packaging material. Aluminum is used more and more widely in the manufacture of containers for canning and storage of agricultural products, 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 also 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.

Aluminum is a chemical element of the third group of the periodic system

we are elements of D. I. Mendeleev. Its atomic number is 13, atomic mass

26.98. Aluminum has no stable isotopes.

Chemical properties

Interaction with non-metals

It interacts with oxygen only in a finely divided state at high temperature:

4Al + 3O 2 \u003d 2Al 2 O 3,

The reaction is accompanied by a large release of heat.

Above 200°C reacts with sulfur to form aluminum sulfide:

2Al + 3S \u003d Al 2 S 3.

At 500°C - with phosphorus, forming aluminum phosphide:

At 800°C it reacts with nitrogen, and at 2000°C it reacts with carbon, forming nitride and carbide:

2Al + N 2 \u003d 2AlN,

4Al + 3C \u003d Al 4 C 3.

It interacts with chlorine and bromine under normal conditions, and with iodine when heated, in the presence of water as a catalyst:

2Al + 3Cl 2 = 2AlCl 3

It does not interact directly with hydrogen.

It forms alloys with metals that contain intermetallic compounds - aluminides, for example, CuAl 2, CrAl 7, FeAl 3, etc.

Interaction with water

Purified from the oxide film, aluminum interacts vigorously with water:

2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2

as a result of the reaction, sparingly soluble aluminum hydroxide is formed and hydrogen is released.

Interaction with acids

Easily interacts with dilute acids, forming salts:

2Al + 6HCl \u003d 2AlCl 3 + 3H 2;

2Al + 3H 2 SO 4 \u003d Al 2 (SO 4) 3 + 3H 2;

8Al + 30HNO 3 \u003d 8Al (NO 3) 3 + 3N 2 O + 15H 2 O (nitrogen and ammonium nitrate can also be a product of nitric acid reduction).

It does not interact with concentrated nitric and sulfuric acids at room temperature; when heated, it reacts to form a salt and an acid reduction product:

2Al + 6H 2 SO 4 \u003d Al 2 (SO 4) 3 + 3SO 2 + 6H 2 O;

Al + 6HNO 3 \u003d Al (NO 3) 3 + 3NO 2 + 3H 2 O.

Interaction with alkalis

Aluminum is an amphoteric metal, it easily reacts with alkalis:

in solution to form sodium tetrahydroxodiquaaluminate:

2Al + 2NaOH + 10H 2 O = 2Na + 3H 2

when fused to form aluminates:

2Al + 6KOH \u003d 2KAlO 2 + 2K 2 O + 3H 2.

Recovery of metals from oxides and salts

Aluminum is an active metal, capable of displacing metals from their oxides. This property of aluminum has found practical application in metallurgy:

2Al + Cr 2 O 3 \u003d 2Cr + Al 2 O 3.

Areas of use

Aluminum has a number of properties that distinguish it from other metals. This is a low density of aluminum, good ductility and sufficient mechanical strength, high thermal and electrical conductivity. Aluminum is non-toxic, non-magnetic and corrosion resistant to a number of chemicals. Thanks to all these properties, as well as its relatively low cost compared to other non-ferrous metals, it has found exceptionally wide application in various branches of modern technology.

A significant part of aluminum is used in the form of alloys with silicon, copper, magnesium, zinc, manganese and other metals. Industrial aluminum alloys usually contain at least two or three alloying elements, which are introduced into aluminum mainly to increase mechanical strength.

The most valuable properties of all aluminum alloys are low density

(2.65÷2.8), high specific strength (ratio of tensile strength to density) and satisfactory resistance to atmospheric corrosion.

Aluminum alloys are divided into wrought and cast. Wrought alloys are subjected to hot and cold working by pressure, so they must have high ductility. Of the wrought alloys, duralumins, alloys of aluminum with copper, magnesium and manganese, have found wide application. Having a low density, mechanical properties of duralumin are close to mild steel grades. From deformable

aluminum alloys, as well as from pure aluminum as a result of pressure treatment (rolling, stamping), sheets, strips, foil, wire, rods of various profiles, pipes are obtained. The consumption of aluminum for the manufacture of these semi-finished products is about 70% of its world production.

The rest of the aluminum is used for the manufacture of foundry alloys, powders, deoxidizers, and for other purposes.

From casting alloys, shaped castings of various configurations are obtained. Aluminum-based casting alloys are widely known - silumins, in which silicon is the main alloying additive (up to 13%).

The use of aluminum and its alloys in all types of transport and, first of all, in air transport, made it possible to solve the problem of reducing the own (“dead”) mass of vehicles and dramatically increasing their efficiency.

applications. Aircraft structures, engines, blocks, cylinder heads, crankcases, gearboxes, pumps and other parts 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, and AC rectifiers. 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 substances 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 agricultural products, 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 reflective surfaces of heating and lighting reflectors and mirrors from it.

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 aluminothermic methods, for steel deoxidation, and welding of 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 terms of production scale and importance in the national economy, aluminum has firmly taken first place among other non-ferrous metals.

We send it into the air and launch it into space, put it on a stove, build buildings from it, make tires, smear it on the skin and treat ulcers with it ... Don't you understand yet? It's about aluminum.

Try to list all the applications of aluminum and be sure to be mistaken. You probably don't even know that many of them exist. Everyone knows that aluminum is the material of aircraft manufacturers. But what about the automotive industry or, let's say. medicine? Did you know that aluminum is an E-137 food additive that is commonly used as a coloring agent to give foods a silvery hue?

Aluminum is an element that easily forms stable compounds with any metals, oxygen, hydrogen, chlorine and many other substances. As a result of such chemical and physical influences, alloys and compounds diametrically different in their properties are obtained.

The use of aluminum oxides and hydroxides

The scope of aluminum is so extensive that in order to protect manufacturers, designers and engineers from unintentional errors, in our country the use of marking aluminum alloys has become mandatory. Each alloy or compound is assigned its own alphanumeric designation, which then allows you to quickly sort them and send them for further processing.

The most common natural aluminum compounds are its oxide and hydroxide. in nature, they exist exclusively in the form of minerals - corundum, bauxite, nepheline, etc. - and as alumina. The use of aluminum and its compounds is associated with the jewelry, cosmetology, medical fields, the chemical industry and construction.

Colored, "pure" (not cloudy) corundums are the jewels known to all of us - rubies and sapphires. However, at their core, they are nothing more than the most common aluminum oxide. In addition to the jewelry sector, the use of aluminum oxide extends to the chemical industry, where it usually acts as an adsorbent, as well as to the production of ceramic dishes. Ceramic pots, pots, cups have remarkable heat-resistant properties precisely because of the aluminum they contain. Aluminum oxide has also found its use as a material for the manufacture of catalysts. Often, aluminum oxides are added to concrete for its better hardening, and glass, to which aluminum is added, becomes heat-resistant.

The list of applications for aluminum hydroxide is even more impressive. Due to its ability to absorb acid and catalyze the human immune system, aluminum hydroxide is used in the manufacture of medicines and vaccines for hepatitis types "A" and "B" and tetanus infection. They are also treated for kidney failure due to the presence of a large number of phosphates in the body. Once in the body, aluminum hydroxide reacts with phosphates and forms inextricable bonds with them, and then naturally excreted from the body.

Hydroxide, due to its excellent solubility and non-toxicity, is often added to toothpaste, shampoo, soap, sunscreens, nourishing and moisturizing face and body creams, antiperspirants, tonics, cleansing lotions, foams, etc. If necessary to evenly and stably dye the fabric, then a little aluminum hydroxide is added to the dye and the color is literally "etched" into the surface of the matter.

Application of aluminum chlorides and sulfates

Chlorides and sulfates are also extremely important aluminum compounds. Aluminum chloride does not occur naturally, but it is quite easy to obtain it industrially from bauxite and kaolin. The use of aluminum chloride as a catalyst is rather one-sided, but practically invaluable for the oil refining industry.

Aluminum sulfates exist naturally as minerals in volcanic rocks and are known for their ability to absorb water from the air. The use of aluminum sulphate extends to the cosmetic and textile industries. In the first, it acts as an additive in antipersperands, in the second - in the form of a dye. An interesting use of aluminum sulfate in the composition of insect repellants. Sulphates not only repel mosquitoes, flies and midges, but also anesthetize the bite site. However, despite the tangible benefits, aluminum sulfates have an ambiguous effect on human health. If you inhale or swallow aluminum sulfate, you can get serious poisoning.

Aluminum alloys - main applications

Artificially obtained compounds of aluminum with metals (alloys), unlike natural formations, can have such properties as the manufacturer himself wishes - it is enough to change the composition and amount of alloying elements. Today, there are almost limitless possibilities for obtaining aluminum alloys and their applications.

The most famous industry for the use of aluminum alloys is the aircraft industry. Aircraft are almost entirely made of aluminum alloys. Alloys of zinc, magnesium and aluminum give unprecedented strength, used in aircraft skins and structural parts.

Aluminum alloys are used similarly in the construction of ships, submarines and small river transport. Here it is most profitable to make superstructures from aluminum, they reduce the weight of the vessel by more than half, without compromising their reliability.

Like airplanes and ships, cars are becoming more and more "aluminum" every year. Aluminum is used not only in body parts, but now it is also frames, beams, pillars and cabin panels. Due to the chemical inertness of aluminum alloys, low susceptibility to corrosion and thermal insulation properties of aluminum alloys, tanks are made for the transport of liquid products.

The use of aluminum in industry is widely known. Oil and gas production would not be where it is today if it were not for the extremely corrosion-resistant, chemically inert aluminum alloy pipelines. Drills made of aluminum weigh several times less, which means they are easy to transport and install. And this is not to mention all kinds of tanks, boilers and other containers ...

Pots, frying pans, baking sheets, ladles and other household utensils are made from aluminum and its alloys. Aluminum cookware conducts heat very well, heats up very quickly, and is easy to clean, does not harm health and food. We bake meat in the oven and bake pies on aluminum foil, oils and margarines, cheeses, chocolates and sweets are packed in aluminum.

An extremely important and promising area is the use of aluminum in medicine. In addition to the uses (vaccines, kidney drugs, adsorbents) mentioned earlier, the use of aluminum in medicines for ulcers and heartburn should also be mentioned.

From all of the above, one conclusion can be drawn - aluminum grades and their application are too diverse to dedicate one small article to them. It is better to write books about aluminum, because it is not for nothing that it is called the "metal of the future".

As the lightest and most ductile metal, it has a wide range of uses. It is resistant to corrosion, has high electrical conductivity, and also easily tolerates sharp temperature fluctuations. Another feature is the appearance of a special film on its surface upon contact with air, which protects the metal.

All these, as well as other features, served as its active use. So, let's find out in more detail what are the applications of aluminum.

This structural metal is widely used. In particular, it was with its use that the aircraft industry, rocket science, the food industry and the manufacture of dishes began their work. Due to its characteristics, aluminum allows to improve the maneuverability of ships due to the lower weight.

Aluminum structures are on average 50% lighter than similar steel products.

Separately, it is worth mentioning the ability of the metal to conduct current. This feature made it the main competitor. It is actively used in the production of microcircuits and in general in the field of microelectronics.

The most popular areas of use are:

Aircraft industry: pumps, engines, housings and other elements;
Rocketry: as a combustible component for rocket fuel;
Shipbuilding: hulls and deck superstructures;
Electronics: wires, cables, rectifiers;
Defense production: machine guns, tanks, aircraft, various installations;
Construction: stairs, frames, finishing;
Railway area: tanks for oil products, parts, frames for wagons;
Automotive: bumpers, radiators;
Life: foil, dishes, mirrors, small appliances;

The wide distribution is explained by the advantages of the metal, but it also has a significant drawback - this is low strength. To minimize it, magnesium is also added to the metal.

As you already understood, aluminum and its compounds have received their main application in electrical engineering (and just technology), everyday life, industry, mechanical engineering, and aviation. Now we will talk about the use of aluminum metal in construction.

This video will tell about the use of aluminum and its alloys:

Use in construction

The use of aluminum by man in the field of construction is determined by its resistance to corrosion. This makes it possible to manufacture structures from it that are planned to be used in aggressive environments, as well as in the open air.

Roofing materials

Aluminum is actively used for. This sheet material, in addition to good decorative, load-bearing and enclosing features, is also distinguished by its affordable cost compared to other roofing materials. At the same time, such a roof does not require routine inspection or repair, and its service life exceeds many existing materials.

By adding other metals to pure aluminum, you can get absolutely any decorative features. Such a roof allows you to have a wide range of colors that will fit perfectly into the overall style.

window sashes

You can find aluminum among lampposts and window frames. If used for a similar purpose, then it will manifest itself as an unreliable and short-lived material.

Steel, on the other hand, will quickly corrode, will have a large binding weight and inconvenience in opening it. In turn, aluminum structures do not have such disadvantages.

The video below will tell about the properties and uses of aluminum:

Wall panels

Aluminum panels are made from alloys of this metal and are used for exterior decoration of houses. They can take the form of ordinary stamped sheets or finished enclosing panels, consisting of sheets, insulation and cladding. In any case, they contain the heat inside the house as much as possible and, having a low weight, do not bear the load on the foundation.

Aluminum is used for the production of products and alloys based on it.

Alloying is the process of introducing additional elements into the melt that improve the mechanical, physical and chemical properties of the base material. Alloying is a general concept of a number of technological procedures carried out at various stages of obtaining a metallic material in order to improve the quality of metallurgical products.

Introduction of various alloying elements in aluminum significantly changes its properties, and sometimes gives it new specific properties.

The strength of pure aluminum does not satisfy modern industrial needs, therefore, for the manufacture of any products intended for industry, not pure aluminum is used, but its alloys.

With different doping increase strength, hardness, heat resistance is acquired and other properties. At the same time, undesirable changes also occur: the electrical conductivity, worsens in many cases corrosion resistance, almost always increases relative density. The exception is alloying with manganese, which not only does not reduce corrosion resistance, but even slightly increases it, and magnesium, which also increases corrosion resistance (if it is not more than 3%) and reduces relative density, since it is lighter than aluminum.

Aluminum alloys

Aluminum alloys according to the method of manufacturing products from them are divided into two groups:
1) deformable (have high ductility when heated),
2) foundry (have good fluidity).

This division reflects the main technological properties of the alloys. To obtain these properties, aluminum is introduced with various alloying elements and in different quantities.

The raw materials for obtaining alloys of both types are not only commercially pure aluminum, but also double alloys of aluminum with silicon, which contain 10-13% Si, and differ slightly from each other in the amount of impurities of iron, calcium, titanium and manganese. The total content of impurities in them is 0.5-1.7%. These alloys are called silumins. In order to obtain wrought alloys, alloying elements soluble in it are mainly introduced into aluminum in an amount not exceeding the limit of their solubility at high temperature. Wrought alloys when heated under pressure treatment should have a homogeneous solid solution structure, providing the highest ductility and the lowest strength. This determines their good workability by pressure.

The main alloying elements in various wrought alloys are copper, magnesium, manganese and zinc, in addition, silicon, iron, nickel and some other elements are also introduced in relatively small quantities.

Duralumin - aluminum alloys with copper

Characteristic hardenable alloys are duralumin - alloys of aluminum with copper, which contain constant impurities of silicon and iron and can be alloyed with magnesium and manganese. The amount of copper in them is in the range of 2.2-7%.

Copper dissolves in aluminum in an amount of 0.5% at room temperature and 5.7% at a eutectic temperature of 548 C.

Heat treatment of duralumin consists of two stages. First, it is heated above the limiting solubility line (usually up to about 500 C). At this temperature, its structure is a homogeneous solid solution of copper in aluminum. By hardening, i.e. rapid cooling in water, this structure is fixed at room temperature. In this case, the solution becomes supersaturated. In this state, i.e. in a state of hardening, duralumin is very soft and ductile.

The structure of hardened duralumin has little stability, and even at room temperature changes spontaneously occur in it. These changes come down to the fact that excess copper atoms are grouped in solution, arranged in an order close to that characteristic of crystals of the chemical compound CuAl. The chemical compound is not yet formed and, moreover, is not separated from the solid solution, but due to the uneven distribution of atoms in the crystal lattice of the solid solution, distortions occur in it, which lead to a significant increase in hardness and strength with a simultaneous decrease in the ductility of the alloy. The process of changing the structure of a hardened alloy at room temperature is called natural aging.

Natural aging occurs especially intensively during the first few hours, but it is completely completed, giving the alloy its maximum strength, after 4-6 days. If the alloy is heated to 100-150 C, then artificial aging. In this case, the process is completed quickly, but the hardening occurs less. This is explained by the fact that at a higher temperature, the diffusion displacements of copper atoms are carried out more easily; therefore, the formation of the CuAl phase is completed and it is separated from the solid solution. The strengthening effect of the obtained phase turns out to be less than the effect of the distortion of the solid solution lattice that occurs during natural aging.

Comparison of the results of aging of duralumin at different temperatures shows that the maximum hardening is provided during natural aging within four days.

Alloys of aluminum with manganese and magnesium

Among non-hardenable aluminum alloys, alloys based on Al-Mn and Al-Mg have gained the most importance.

manganese and magnesium, as well as copper, have a limited solubility in aluminum, which decreases with decreasing temperature. However, the effect of hardening during their heat treatment is small. This is explained as follows. In the process of crystallization in the manufacture of alloys containing up to 1.9% Mn, excess manganese liberated from the solid solution should have formed with aluminum a chemical compound Al (MnFe) soluble in it, which does not dissolve in aluminum. Consequently, subsequent heating above the limiting solubility line does not ensure the formation of a homogeneous solid solution, the alloy remains heterogeneous, consisting of a solid solution and Al (MnFe) particles, and this leads to the impossibility of hardening and subsequent aging.

In the case of the Al-Mg system, the reason for the lack of hardening during heat treatment is different. With a magnesium content of up to 1.4%, there can be no hardening, since within these limits it dissolves in aluminum at room temperature and no precipitation of excess phases occurs. At a higher magnesium content, quenching followed by chemical aging leads to the release of an excess phase - the chemical compound MgAl.

However, the properties of this compound are such that the processes preceding its isolation, and then the resulting inclusions, do not cause a noticeable hardening effect. Despite this, the introduction of both manganese and magnesium in aluminum is beneficial. They increase its strength and corrosion resistance (with a magnesium content of not more than 3%). In addition, magnesium alloys are lighter than pure aluminum.

Other alloying elements

Also, to improve some of the characteristics of aluminum, the following are used as alloying elements:

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 internal combustion engine parts (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 engineering (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 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 aluminium-cadmium bearing alloys.

Cadmium. 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.

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.

Application of aluminum alloys

Most aluminum alloys have high corrosion resistance in the natural atmosphere, sea water, solutions of many salts and chemicals, and in most foods. The latter property, combined with the fact that aluminum does not destroy vitamins, allows it to be widely used. in the production of tableware. Aluminum alloy structures are often used in sea water. Aluminum is widely used in construction in the form of cladding panels, doors, window frames, and electrical 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. Aluminum is also widely used in mechanical engineering, because has good physical qualities.

But the main industry, currently simply unthinkable without the use of aluminum, is, of course, aviation. It is in aviation that all the important characteristics of aluminum have been most fully used.