What is the hardness of aluminum - Metals and their processing

Physical and chemical properties of aluminum

Aluminum is a metal whose content in nature is the highest among all known. The late start of its use is due to the fact that, since it has high chemical activity, it is found in the earth’s crust only as part of various chemical compounds. The recovery of pure metal is associated with a number of difficulties, which became possible to overcome only with the development of metal mining technologies.

Pure aluminum is a soft, malleable metal with a silvery-white color. This is one of the lightest metals, which, moreover, lends itself well to various mechanical processing, stamping, rolling, and casting. In the open air, it is almost instantly covered with a thin and durable film of oxide, which counteracts further oxidation.

Aluminum appearance

The mechanical properties of aluminum, such as softness, malleability for stamping, ease of processing, have become widespread in many industries. Aluminum is especially often used in alloys with other metals.

The physical and chemical properties of aluminum alloys have given rise to their widespread use as structural materials that reduce the overall weight of a structure without compromising its strength properties.

Physical properties

Aluminum does not have any unique physical properties, but their combination makes the metal one of the most widely sought after.

Pure aluminum has a Mohs hardness of three, which is significantly lower than most metals. This fact is practically the only obstacle to the use of pure metal.

If you carefully consider the table of physical properties of aluminum, you can highlight the following qualities:

Low density (2.7 g/cm3);
High plasticity;
Low electrical resistivity (0.027 Ohm mm2/m);
High thermal conductivity (203.5 W/(m K));
High reflectivity;
Low melting point (660°C).

Such physical properties of aluminum as high ductility, low melting point, excellent casting qualities allow the use of this metal in its pure form and as part of alloys based on it for the production of products of any complex configuration.

At the same time, it is one of the few metals whose fragility does not increase when cooled to ultra-low temperatures. This property has determined one of the areas of application in structural elements of cryogenic technology and equipment.

Aluminum parts

Aluminum-based alloys have significantly higher strength, comparable to the strength of some types of steel. The most widespread are alloys with the addition of magnesium, copper and manganese - duralumin alloys and with the addition of silicon - silumins. The first group is distinguished by high strength, and the latter has one of the best casting qualities.

The low melting point reduces production costs and the cost of technological processes in the production of structural materials based on aluminum and its alloys.

For the manufacture of mirrors, such qualities as a high reflection coefficient, comparable to that of silver, and the ease and manufacturability of vacuum deposition of aluminum films onto various load-bearing surfaces (plastics, metal, glass) are used.

When melting aluminum and performing casting, special attention is paid to the ability of the melt to absorb hydrogen. Without having any effect at the chemical level, hydrogen helps to reduce density and strength due to the formation of microscopic pores when the melt solidifies.

Due to their low density and low electrical resistance (not much higher than copper), pure aluminum wires are primarily used for transmitting electricity in power lines, across the entire range of currents and voltages in electrical engineering, as an alternative to copper power and winding wires.

The resistance of copper is somewhat lower, so aluminum wires must be used with a larger cross-section, but the final mass of the product and its cost are several times less. The only limitation is the slightly lower strength of aluminum and high resistance to soldering due to the oxide film on the surface.

The presence of a strong electrochemical potential upon contact with a metal such as copper plays an important role. As a result, a strong oxide film with high electrical resistance is formed at the point of mechanical contact between copper and aluminum. This phenomenon leads to heating of the junction until the conductors melt.

There are strict restrictions and recommendations on the use of aluminum in electrical engineering.

Aluminum in construction

High ductility makes it possible to produce thin foil, which is used in the production of high-capacity capacitors.

The lightness of aluminum and its alloys have become fundamental when used in the aerospace industry in the manufacture of most aircraft structural elements: from load-bearing structures to skin elements, instrument housings and equipment.

Chemical properties

Being a fairly reactive metal, aluminum actively resists corrosion. This occurs due to the formation of a very strong oxide film on its outer surface under the influence of oxygen.

A durable oxide film protects the surface well even from strong acids such as nitric and sulfuric acids. This quality is widespread in chemistry and industry for transporting concentrated nitric acid.

Chemical properties of aluminum

The film can be destroyed with highly diluted nitric acid, alkalis when heated, or through contact with mercury, when an amalgam forms on the surface. In these cases, the oxide film is not a protective factor and aluminum actively interacts with acids, alkalis and oxidizing agents. The oxide film is also easily destroyed in the presence of halogens (chlorine, bromine). Thus, hydrochloric acid HCl interacts well with aluminum under any conditions.

The chemical properties of aluminum depend on the purity of the metal. The use of alloying additives of certain metals, in particular manganese, makes it possible to increase the strength of the protective film, thereby increasing the corrosion resistance of aluminum. Some metals, for example, nickel and iron, help reduce corrosion resistance, but increase the heat resistance of alloys.

The oxide film on the surface of aluminum products plays a negative role during welding work. The instantaneous oxidation of the molten metal pool during welding does not allow the formation of a weld seam, since aluminum oxide has a very high melting point.

To weld aluminum, special welding machines with a non-consumable electrode (tungsten) are used. The process itself is carried out in an inert gas environment - argon. In the absence of an oxidation process, the welding seam is strong and monolithic.

Some alloying additives in alloys further improve the welding properties of aluminum.

Pure aluminum practically does not form toxic compounds, therefore it is actively used in the food industry in the production of kitchenware, food packaging, and drink containers. Only some inorganic compounds can have a negative effect. Research has also established that aluminum is not used in the metabolism of living beings, its role in life is negligible.

Source: https://stankiexpert.ru/spravochnik/materialovedenie/svoystva-aluminiia.html

Materials Science

Aluminum is a silver-white metal, characterized by low density, high electrical conductivity, melting point 660° C. The mechanical properties of aluminum are low, therefore, in its pure form, it is used to a limited extent as a structural material.

To improve the physical, mechanical and technological properties, aluminum is alloyed with various elements (Cu, Cr, Mg, Si, Zn, Mn, Ni).

Depending on the content of permanent impurities, they are distinguished:

high purity aluminum grade A999 (0.001% impurities);
high purity aluminum - A935, A99, A97, A95 (0.0050.5% impurities);
technical aluminum – A35, A3, A7, A5, A0 (0.150.5% impurities).

Technical aluminum is produced in the form of semi-finished products for further processing into products. High purity aluminum is used for the manufacture of foil, conductive and cable products.

Aluminum-based alloys are classified according to the following criteria:

by manufacturing technology;
by the degree of hardening after heat treatment;
according to operational properties.

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Wrought alloys

Alloys that cannot be strengthened by heat treatment include:

aluminum with manganese grade AMts;
aluminum with magnesium grades AMG; AMgZ, AMg5V, AMg5P, AMg6.

These alloys have high ductility, corrosion resistance, can be easily stamped and welded, but have low strength. They are used to make gasoline tanks, wire, rivets, as well as welded tanks for liquids and gases, and car parts.

In the group of deformable aluminum alloys, hardened by heat treatment, the following alloys are distinguished:

normal strength;
high-strength alloys;
heat-resistant alloys;
alloys for forging and stamping.

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Normal strength alloys

Alloys of normal strength include alloys of the Aluminum + Copper + Magnesium system (duralumins, duralumins), which are marked with the letter “D”.
Duralumins (D1, D16, D18) are characterized by high strength, sufficient hardness and toughness.
To harden alloys, quenching followed by cooling in water is used. Hardened duralumins undergo aging, which increases their corrosion resistance.

Duralumins are widely used in the aircraft industry: propeller blades are made from alloy D1, load-bearing elements of aircraft fuselages are made from alloy D16, alloy D18 is one of the main rivet materials.

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High-strength aluminum alloys (B93, B95, B96) belong to the Aluminum + Zinc + Magnesium + Copper system. Manganese and chromium are used as alloying additives, which increase the corrosion resistance and aging effect of the alloy.

To achieve the required strength properties, the alloys are hardened followed by aging.
High-strength alloys are superior in strength to duralumin, but are less ductile and more sensitive to stress concentrators (notches).

These alloys are used to make highly loaded external structures in the aircraft industry - parts of frames, landing gear and skin.

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Heat-resistant alloys

Heat-resistant aluminum alloys (AK4-1, D20) have a complex chemical composition, alloyed with iron, nickel, copper and other elements. Alloys are given heat resistance by alloying, which slows down diffusion processes.

Parts made of heat-resistant alloys are used after hardening and artificial aging and can be operated at temperatures up to 300° C.

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Alloys for forging and stamping

Alloys for forging and stamping (AK2, AK4, AK6, AK8) belong to the Aluminum + Copper + Magnesium system with silicon additives.
The alloys are used after hardening and aging for the manufacture of medium-loaded parts with complex shapes (AK6) and highly loaded stamped parts - pistons, propeller blades, pump impellers, etc.

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Casting alloys

For the manufacture of parts by casting, aluminum alloys of the Al-Si, Al-Cu, Al-Mg systems are used. To improve the mechanical properties, the alloys are alloyed with titanium, boron, and vanadium.

The main advantage of casting alloys is high fluidity, low shrinkage, and good mechanical properties.

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Copper and its alloys

Olympics and tests

Source: http://kat.ru/materialovedenie/7-1_alumin/index.shtml

Features of the composition, properties and characteristics of aluminum

Aluminum is the most abundant metal in the earth's crust. It belongs to the group of light metals, has a low density and melting point.

At the same time, ductility and electrical conductivity are at a high level, which ensures its widespread use. So, let's find out what the specific melting temperature of aluminum and its alloys (ex.

in comparison with iron and lead), thermal and electrical conductivity, density, other properties, as well as what are the features of the structure of aluminum alloys and their chemical composition.

To begin with, the structure and chemical composition of aluminum are subject to our consideration. The tensile strength of pure aluminum is extremely small and amounts to up to 90 MPa. If manganese, copper, zinc or magnesium are added to its composition in small proportions, the strength can increase to 700 MPa. The use of special heat treatment will lead to the same result.

The metal with the highest purity (99.99% aluminum) can be used for special and laboratory purposes; in other cases, aluminum with technical purity is used. The most common impurities in it may be silicon and iron, which are practically insoluble in aluminum. As a result of their addition, ductility decreases and the strength of the final metal increases.

The structure of aluminum is represented by unit cells, which in turn consist of four atoms. Theoretically, the density of this metal is 2698 kg/m3.

Now let's talk about the properties of aluminum metal.

This video will tell you about the structure of aluminum:

The properties of the metal include its high thermal and electrical conductivity, immunity to corrosion, high ductility and resistance to low temperatures. Moreover, its main property is its low density (about 2.7 g/cm3).

The mechanical, technological, as well as physical and chemical properties of this metal are directly dependent on the impurities included in its composition. Its natural components include silicon and iron.

Let's find out further what is the melting point of aluminum and its alloys

Main settings

The density of aluminum is 2.7*103 kg/m3;
Specific gravity - 2.7 g/cm3;
Aluminum melting point 659°C;
Boiling point 2000°C;
The coefficient of linear expansion is 22.9 * 106(1/deg).

Now the thermal conductivity and electrical conductivity of aluminum are subject to consideration.

This video compares the melting points of aluminum and other commonly used metals:

An important indicator of aluminum is its electrical conductivity, which is second only to gold, silver and copper. The high coefficient of electrical conductivity in combination with low density makes the material highly competitive in the cable and wire industry.

In addition to the main impurities, this indicator is also affected by titanium, manganese and chromium. If aluminum is intended for the production of current conductors, then the total amount of impurities should not exceed 0.01%.

The electrical conductivity indicator may vary depending on the state in which the aluminum is located. The process of long-term annealing increases this indicator, and cold hardening, on the contrary, reduces it.
Specific resistance at a temperature of 200C, depending on the type of metal, is in the range of 0.0277-0.029 μOhm*m.

Thermal conductivity

The thermal conductivity coefficient of the metal is about 0.50 cal/cm*s*C and increases with the degree of its purity.

This value is less than that of copper and silver, but greater than that of other metals. Thanks to him, aluminum is actively used in the production of heat exchangers and radiators.

Corrosion resistance

The metal itself is a chemically active substance, which is why it is used in aluminothermy. Upon contact with air, a thin film of aluminum oxide is formed on it, which has chemical inertness and high strength. Its main purpose is to protect the metal from the subsequent oxidation process, as well as from the effects of corrosion.

If the aluminum is of high purity, then this film has no pores, completely covers its surface and provides reliable adhesion. As a result, the metal is resistant not only to water and air, but also to alkalis and inorganic acids.
In places where impurities are located, the protective layer of the film may be damaged. Such places become vulnerable to corrosion. Therefore, pitting corrosion may occur on the surface. If the grade contains 99.7% aluminum and less than 0.25% iron, the corrosion rate is 1.1, with an aluminum content of 99.0% this figure increases to 31.
The iron contained also reduces the metal's resistance to alkalis, but does not change the resistance to sulfuric and nitric acids.

Interaction with various substances

When aluminum has a temperature of 1000C, it is able to interact with chlorine. Regardless of the degree of heating, aluminum dissolves hydrogen, but does not react with it. That is why it is the main component of the gases that are present in the metal.

In general, aluminum is stable in the following environments:

Fresh and sea water;
Magnesium, sodium and ammonium salts;
Sulfuric acid;
Weak solutions of chromium and phosphorus;
Ammonia solution;
Acetic, malic and other acids.

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Aluminum is not resistant:

Sulfuric acid solution;
Hydrochloric acid;
Caustic alkalis and their solution;
Oxalic acid.

Read below about the toxicity and environmental friendliness of aluminum.

The electrical conductivities of copper and aluminum, as well as other comparisons between the two metals, are presented in the table below.

Comparison of the characteristics of aluminum and copper

Although aluminum is very common, it is not used in metabolism by any living creature. It has a slight toxic effect, but many of its inorganic compounds, which dissolve in water, can remain in this state for a long time and negatively affect living organisms. The most toxic substances are acetates, chlorides and nitrates.

According to standards, drinking water may contain 0.2-0.5 mg per 1 liter.

This video contains even more useful information about the properties of aluminum:

Source: http://stroyres.net/metallicheskie/vidyi/tsvetnyie/alyuminiy/osobennosti-svoystv-i-harakteristik.html

Mechanical properties of aluminum

The mechanical properties of aluminum, like other materials, are properties that are associated with the elastic and inelastic response of the material to the application of a load to it, including the relationship between stress and strain. Examples of mechanical properties are:

modulus of elasticity (tensile, compressive, shear)
tensile strength (tensile, compressive, shear)
yield strength
fatigue limit
elongation (relative) at break
hardness.

Mechanical properties are often mistakenly referred to as physical properties.

The mechanical properties of materials, including aluminum and its alloys, that are obtained by tensile testing of the material, such as tensile modulus, tensile strength, tensile yield strength and elongation, are called tensile mechanical properties.

Elastic modulus

The modulus of elasticity, often called Young's modulus, is the ratio of the stress that is applied to a material to the corresponding strain in the range where they are directly proportional to each other.

There are three types of stresses and, accordingly, three types of elastic moduli for any material, including aluminum:

tensile modulus of elasticity
compressive modulus of elasticity
shear modulus of elasticity (shear modulus of elasticity).

Table - Tensile elastic moduli of aluminum and other metals [1]

Tensile strength

The ratio of the maximum load before failure of a sample when testing it in tension to the original cross-sectional area of the sample. The terms “tensile strength” and “tensile strength” are also used.

Yield strength

The stress required to achieve a specified small plastic deformation in aluminum or other material under uniaxial tensile or compressive load.

If the plastic deformation under tensile load is specified as 0.2%, then the term “yield strength 0.2%” (Rp0.2) is used.

Figure - Typical stress-strain diagram
for aluminum alloys

Elongation (at break)

Often called "relative elongation". An increase in the distance between two marks on a test specimen that occurs as a result of the specimen deforming under tension until it breaks between the marks.

The amount of elongation depends on the cross-sectional dimensions of the sample. For example, the amount of elongation that is obtained when testing an aluminum sheet specimen will be lower for a thin sheet than for a thick sheet. The same applies to extruded aluminum profiles.

Extension A

Percentage elongation after specimen rupture at an initial mark spacing of 5.65 √ S0, where S0 is the initial cross-sectional area of the test specimen. The outdated designation of this quantity A5 is currently not used. A similar value in Russian-language documents is designated δ5.

It is easy to check that for round samples this distance between the original marks is calculated as 5·d.

Extension A50mm

The percentage elongation after specimen rupture, relative to the original length between the 50 mm marks and the constant original width of the test specimen (typically 12.5 mm). In the USA, a distance between marks of 2 inches is used, that is, 50.8 mm.

Shear strength

The maximum specific stress, that is, the maximum load divided by the original cross-sectional area that a material can withstand when tested in shear. Shear strength is typically 60% of tensile strength.

Shear strength is an important quality characteristic of rivets, including aluminum ones.

Poisson's ratio

The relationship between longitudinal elongation and transverse shortening of a section in a uniaxial test. For aluminum and all aluminum alloys in all states, Poisson's ratio is typically 0.33 [2].

Hardness

The resistance of a metal to plastic deformation, usually measured by making an impression.

Brinell Hardness (HB)

Penetration resistance of a spherical indenter under standardized conditions.

For aluminum and aluminum alloys, the hardness of NV is approximately equal to 0.3 Rm, where Rm is the tensile strength expressed in MPa [2].

If a tungsten carbide indenter is used, the designation HBW is used.

Vickers Hardness (HV)

Penetration resistance of a square pyramid diamond indenter under standardized conditions. Hardness HV is approximately equal to 1.10·HB [2].

Fatigue

The tendency of a metal to fail under prolonged cyclic stress that is well below its tensile strength.

Fatigue strength

The maximum stress amplitude that a product can withstand for a given number of loading cycles. Typically expressed as the stress amplitude that gives a 50% probability of failure after a given number of loading cycles [2].

Fatigue endurance

The limiting stress below which a material will withstand a specified number of stress cycles [2].

Mechanical properties of aluminum and aluminum alloys

The tables below [3] present typical mechanical properties of aluminum and aluminum alloys:

tensile strength
tensile yield strength
tensile elongation
fatigue endurance
hardness
elastic modulus

Mechanical properties are presented separately:

for aluminum alloys hardened by work hardening.
for aluminum alloys, hardened by heat treatment.

These mechanical properties are typical. This means that they are only suitable for comparative purposes and not for engineering calculations. In most cases, they are average values for various product sizes, shapes and manufacturing methods.

Source: https://aluminium-guide.ru/mexanicheskie-svojstva-deformiruemyx-alyuminievyx-splavov/

Chemical and physical properties of aluminum. Physical properties of aluminum hydroxide:

This lightweight metal with a silvery-white tint is found almost everywhere in modern life. The physical and chemical properties of aluminum allow it to be widely used in industry. The most famous deposits are in Africa, South America, and the Caribbean. In Russia, bauxite mining sites are located in the Urals. The world leaders in aluminum production are China, Russia, Canada, and the USA.

Al mining

In nature, this silvery metal, due to its high chemical activity, is found only in the form of compounds. The most well-known geological rocks containing aluminum are bauxite, alumina, corundum, and feldspar. Bauxite and alumina are of industrial importance; it is the deposits of these ores that make it possible to extract aluminum in its pure form.

Properties

The physical properties of aluminum make it easy to draw blanks of this metal into wire and roll it into thin sheets. This metal is not durable; to increase this indicator during smelting, it is alloyed with various additives: copper, silicon, magnesium, manganese, zinc.

For industrial purposes, another physical property of aluminum is important - its ability to quickly oxidize in air. The surface of an aluminum product under natural conditions is usually covered with a thin oxide film, which effectively protects the metal and prevents its corrosion.

When this film is destroyed, the silver metal quickly oxidizes, and its temperature increases noticeably.

Internal structure of aluminum

The physical and chemical properties of aluminum largely depend on its internal structure. The crystal lattice of this element is a type of face-centered cube.

This type of lattice is inherent in many metals, such as copper, bromine, silver, gold, cobalt and others. High thermal conductivity and the ability to conduct electricity have made this metal one of the most popular in the world.

The remaining physical properties of aluminum, the table of which is presented below, fully reveal its properties and show the scope of their application.

Aluminum alloying

The physical properties of copper and aluminum are such that when a certain amount of copper is added to an aluminum alloy, its crystal lattice becomes distorted, and the strength of the alloy itself increases. Alloying of light alloys is based on this property of Al to increase their strength and resistance to aggressive environments.

The explanation for the hardening process lies in the behavior of copper atoms in the aluminum crystal lattice. Cu particles tend to fall out of the Al crystal lattice and are grouped in its special areas.

Where copper atoms form clusters, a CuAl2 mixed-type crystal lattice is formed, in which silver metal particles are simultaneously included in both the general aluminum crystal lattice and the CuAl2 mixed-type lattice.

The strength of internal connections in a distorted lattice is much greater than in a normal one. This means that the strength of the newly formed substance is much higher.

Aluminum burning

The physical properties of aluminum allow it to react with oxygen. If the powder of this metal or aluminum foil is heated, it flares up and burns with a white, blinding flame. At the end of the reaction, aluminum oxide Al2O3 is formed.

Alumina

The resulting aluminum oxide has the geological name alumina. Under natural conditions, it occurs in the form of corundum - hard transparent crystals. Corundum is highly hard, with a hardness rating of 9. Corundum itself is colorless, but various impurities can turn it red and blue, resulting in precious stones known in jewelry as rubies and sapphires.

The physical properties of aluminum oxide allow these gemstones to be grown in artificial conditions. Industrial gemstones are used not only for jewelry, they are used in precision instrument making, watch making and other things. Artificial ruby crystals are also widely used in laser devices.

A fine-grained variety of corundum with a large number of impurities, applied to a special surface, is known to everyone as emery. The physical properties of aluminum oxide explain the high abrasive properties of corundum, as well as its hardness and resistance to friction.

Aluminum hydroxide

Al2 (OH)3 is a typical amphoteric hydroxide. In combination with an acid, this substance forms a salt containing positively charged aluminum ions; in alkalis it forms aluminates. The amphoteric nature of a substance is manifested in the fact that it can behave both as an acid and as an alkali. This compound can exist in both jelly and solid form.

It is practically insoluble in water, but reacts with most active acids and alkalis. The physical properties of aluminum hydroxide are used in medicine; it is a popular and safe means of reducing acidity in the body; it is used for gastritis, duodenitis, and ulcers.

In industry, Al2 (OH)3 is used as an adsorbent; it perfectly purifies water and precipitates harmful elements dissolved in it.

Industrial use

Aluminum was discovered in 1825. At first, this metal was valued higher than gold and silver. This was explained by the difficulty of extracting it from the ore. The physical properties of aluminum and its ability to quickly form a protective film on its surface made the study of this element difficult. Only at the end of the 19th century was a convenient method for melting a pure element suitable for use on an industrial scale discovered.

Lightness and ability to resist corrosion are the unique physical properties of aluminum. Alloys of this silvery metal are used in rocketry, automobile, ship, aircraft and instrument making, and in the production of cutlery and tableware.

As a pure metal, Al is used in the manufacture of parts for chemical equipment, electrical wires and capacitors. The physical properties of aluminum are such that its electrical conductivity is not as high as that of copper, but this disadvantage is compensated by the lightness of the metal in question, which makes it possible to make aluminum wires thicker. So, with the same electrical conductivity, an aluminum wire weighs half as much as a copper wire.

No less important is the use of Al in the aluminizing process. This is the name given to the reaction of saturating the surface of a cast iron or steel product with aluminum in order to protect the base metal from corrosion when heated.

Currently, the known reserves of aluminum ores are quite comparable to the needs of people for this silvery metal. The physical properties of aluminum can still present many surprises to its researchers, and the scope of application of this metal is much wider than one might imagine.

Source: https://www.syl.ru/article/187993/new_himicheskie-i-fizicheskie-svoystva-alyuminiya-fizicheskie-svoystva-gidroksida-alyuminiya

Physical properties of aluminum table

Aluminum appearance

The mechanical properties of aluminum, such as softness, malleability for stamping, ease of processing, have become widespread in many industries. Aluminum is especially often used in alloys with other metals.

Aluminum hard or soft

Aluminum is a low-melting, ductile and soft metal, which is why it is often used by craftsmen to make various parts at home.

But aluminum has a drawback. It has a very unpresentable appearance due to the protective film formed on its surface.

In other words, aluminum darkens in air, and when used, it gets your hands dirty, because... the film is unstable. To remedy the situation, aluminum is anodized.

We'll talk about how to do this at home in our article.

Anodizing aluminum: what is it?

As already mentioned at the very beginning, aluminum, when interacting with oxygen in the air, oxidizes.

An oxide film forms on its surface, which is very unstable to mechanical damage.

To secure this film and protect it from abrasion, the aluminum is anodized.

How does the property of aluminum parts change after anodizing? That's how:

the top layer of metal is strengthened;
visual and tactile alignment of small errors in the metal surface (scratches, pinhole damage, etc.) occurs;
the process of applying coloring matter to an aluminum workpiece is improved;
the part takes on a more presentable appearance;
it becomes possible to imitate various metals (silver, platinum, gold and even pearls).

Hard anodizing of aluminum: advantages and disadvantages

Anodizing aluminum at home can be done in two ways: hard (cold) and warm.

The latter, due to its complexity, is practically not used at home, but hard anodizing has become widespread among craftsmen.

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This process has its advantages and disadvantages.

The first include such as obtaining a thick protective layer that has good strength characteristics, as well as the formation of a high-strength anti-corrosion film on the metal surface.

Among the shortcomings, one is noted: the inability to retain a uniform layer of organic-based dye on its surface.

The dye applies unevenly and is not durable.

However, during the process of hard anodizing, the workpiece itself is painted in natural colors from greenish, through yellowish-brown to deep gray.

What is needed for hard anodizing

Materials and equipment you will need:

Anodizing to color change

The entire process of anodizing at home can be divided into several stages.

But first I would like to dwell on the process of industrial cold anodization, which occurs using a solution of sulfuric acid.

As a result of this process, active gas evolution occurs, and volatile gases are explosive. That is why it is not recommended to carry out a similar process at home.

Home anodizing technology is safer. Let's talk about its main stages in more detail.

Preparing the necessary solutions
For hard anodizing, two types of solution are prepared in different containers: one is saline, the other is soda, the basis for which is drinking distilled water of medium temperature (40-50 degrees). You will need nine times more soda solution than saline solution, and therefore an appropriate container is selected for it. Salt is added to warm water with constant stirring (to another soda). Saturated solutions are prepared, i.e. salt and soda are added until a precipitate begins to form. After this, the solutions must be filtered several times. Remember that the quality of anodization depends on the quality of the solutions (their transparency and purity). Before the hard anodizing process itself, the solutions are mixed in a ratio of 1 part salt and 9 parts soda.
We prepare the workpiece for anodizing.
Well, everything is simple here. The workpiece must be thoroughly sanded and degreased.
We anodize.
So, let's start anodizing. The parts must be placed in the bath so that they are completely immersed in the solution and do not touch the bottom or walls of the bath. Then an electric current is applied: to the bath “minus”, to the workpiece “plus”. The workpieces remain under the influence of tension in the bath until they change color. Then the current is turned off, the workpieces are removed and thoroughly washed in running water. Afterwards, the part is placed in a manganese solution, where traces of the salt-soda solution are finally removed from the surface of the part. Then we wash it again. Do you see any stains or streaks on the workpiece? So everything went well.
We fix the surface layer.
As a result of anodization, a film was formed with a large number of pores that need to be closed. This is done by simply boiling in distilled water for half an hour.
Varnish or paint.
To do this, place the anodized workpiece in a container with varnish or aniline paint (10%). That's it, the part is ready.

As you can see, the anodizing process at home is simple and accessible to everyone.

Author angor58

Source: https://steelfactoryrus.com/alyuminiy-tverdyy-ili-myagkiy/

Hardness of metals. Metal hardness table

In order for parts and mechanisms to serve for a long time and reliably, the materials from which they are made must meet the necessary operating conditions. That is why it is important to control the permissible values of their main mechanical parameters. Mechanical properties include hardness, strength, impact strength, and ductility. The hardness of metals is a primary structural characteristic.

Concept

The hardness of metals and alloys is the property of a material to create resistance when another body penetrates its surface layers, which does not deform or collapse under accompanying loads (indenter). Determined for the purpose of:

obtaining information about acceptable design features and operational capabilities;
state analysis under the influence of time;
monitoring the results of temperature treatment.

The strength and aging resistance of the surface partly depend on this indicator. Both the source material and finished parts are examined.

Research options

The indicator is a value called the hardness number. There are various methods for measuring the hardness of metals. The most accurate studies involve the use of various types of calculations, indenters and corresponding hardness testers:

Brinell: the essence of the apparatus is pressing a ball into the metal or alloy being tested, calculating the diameter of the indentation and subsequent mathematical calculation of the mechanical parameter.
Rockwell: Uses a ball or diamond cone tip. The value is displayed on a scale or determined by calculation.
Vickers: The most accurate measurement of metal hardness using a diamond pyramid tip.

To determine parametric correspondences between indicators of different measurement methods for the same material, there are special formulas and tables.

Factors that determine the measurement option

In laboratory conditions, if the necessary range of equipment is available, the choice of research method is carried out depending on certain characteristics of the workpiece.

Approximate value of the mechanical parameter. For structural steels and materials with low hardness up to 450-650 HB, the Brinell method is used; for tool, alloy steels and other alloys - Rockwell; for hard alloys – Vickers.
Dimensions of the test sample. Particularly small and thin parts are examined using a Vickers hardness tester.
The thickness of the metal at the measurement location, in particular the cemented or nitrided layer.

All requirements and compliance are documented by GOST.

Features of the Brinell technique

Hardness testing of metals and alloys using a Brinell hardness tester is carried out with the following features:

Indenter - a ball made of alloy steel or tungsten carbide alloy with a diameter of 1, 2, 2.5, 5 or 10 mm (GOST 3722-81).
Duration of static indentation: for cast iron and steel - 10-15 s, for non-ferrous alloys - 30, a duration of 60 s is also possible, and in some cases - 120 and 180 s.
Limit value of the mechanical parameter: 450 HB when measured with a steel ball; 650 HB when using carbide.
Possible loads. Using the weights included in the kit, the actual deformation force on the test sample is adjusted. Their minimum permissible values: 153.2, 187.5, 250 N; maximum – 9807, 14710, 29420 N (GOST 23677-79).

Using formulas, depending on the diameter of the selected ball and the material being tested, the corresponding permissible indentation force can be calculated.

Alloy type	Mathematical load calculation
Steel, nickel and titanium alloys	30D2
Cast iron	10D2, 30D2
Copper and copper alloys	5D2, 10D2, 30D2
Light metals and alloys	2.5D2, 5D2, 10D2, 15D2
Lead, tin	1D2

Example notation:

400HB10/1500/20, where 400HB is the Brinell hardness of the metal; 10 – ball diameter, 10 mm; 1500 – static load, 1500 kgf; 20 – period of indentation, 20 s.

To establish accurate figures, it is rational to examine the same sample in several places, and determine the overall result by finding the average value of the obtained ones.

Determination of hardness using the Brinell method

The research process proceeds in the following sequence:

Checking the part for compliance with the requirements (GOST 9012-59, GOST 2789).
Checking the health of the device.
Selecting the required ball, determining the possible force, installing weights for its formation, and the period of indentation.
Starting the hardness tester and deforming the sample.
Measuring the diameter of the recess.
Empirical calculation.

HB=F/A,

where F – load, kgf or N; A – print area, mm2.

НВ=(0.102*F)/(π*D*h),

where D is the diameter of the ball, mm; h – indentation depth, mm.

The hardness of metals measured by this method has an empirical connection with the calculation of strength parameters. The method is accurate, especially for soft alloys. It is fundamental in systems for determining the values of this mechanical property.

Features of the Rockwell technique

This measurement method was invented in the 20s of the 20th century, and is more automated than the previous one. Used for harder materials. Its main characteristics (GOST 9013-59; GOST 23677-79):

Availability of a primary load of 10 kgf.
Holding period: 10-60 s.
Limit values of possible indicators: HRA: 20-88; HRB: 20-100; HRC: 20-70.
The number is visualized on the dial of the hardness tester and can also be calculated arithmetically.
Scales and indenters. There are 11 different scales depending on the type of indenter and the maximum permissible static load. The most common in use: A, B and C.

A: diamond cone tip, apex angle 120˚, total permissible static influence force – 60 kgf, HRA; Thin products, mainly rolled products, are being studied.

C: also a diamond cone, designed for a maximum force of 150 kgf, HRC, suitable for hard and hardened materials.

B: 1.588 mm ball, made of hardened steel or hard tungsten carbide, 100 kgf, HRB, used to evaluate the hardness of annealed products.

A ball-shaped tip (1.588 mm) is applicable for Rockwell scales B, F, G. There are also scales E, H, K, for which a ball with a diameter of 3.175 mm is used (GOST 9013-59).

The number of tests performed with a Rockwell hardness tester on one area is limited by the size of the part. A repeat test is allowed at a distance of 3-4 diameters from the previous place of deformation. The thickness of the tested product is also regulated. It should be no less than the tip penetration depth increased by 10 times.

Example notation:

50HRC is the Rockwell hardness of a metal, measured using a diamond tip, its number is 50.

Rockwell Study Design

Measuring metal hardness is more simplified than for the Brinell method.

Assessment of the dimensions and surface characteristics of the part.
Checking the health of the device.
Determination of tip type and permissible load.
Sample installation.
Implementation of a primary force on the material of 10 kgf.
Exercising full appropriate effort.
Reading the resulting number on the dial scale.

A mathematical calculation is also possible to accurately determine the mechanical parameter.

Provided that a diamond cone is used with a load of 60 or 150 kgf:

HR=100-((Hh)/0.002;

when performing a test with a ball under a force of 100 kgf:

HR=130-((Hh)/0.002,

where h is the penetration depth of the indenter at a primary force of 10 kgf; H – indenter penetration depth at full load; 0.002 is a coefficient that regulates the amount of movement of the tip when the hardness number changes by 1 unit.

Rockwell's method is simple, but not accurate enough. At the same time, it allows the measurement of mechanical properties for hard metals and alloys.

Characteristics of the Vickers technique

Determining the hardness of metals using this method is the simplest and most accurate. The hardness tester works by pressing a diamond pyramidal tip into the sample.

Key Features:

Indenter: diamond pyramid with apex angle 136°.
Maximum permissible load: for alloy cast iron and steel - 5-100 kgf; for copper alloys - 2.5-50 kgf; for aluminum and alloys based on it - 1-100 kgf.
Static load holding period: from 10 to 15 s.
Test materials: steel and non-ferrous metals with a hardness of more than 450-500 HB, including products after chemical-thermal treatment.

Example notation:

700HV20/15,

where 700HV is the Vickers hardness number; 20 – load, 20 kgf; 15 – period of static force, 15 s.

Vickers study sequence

The procedure is extremely simplified.

Checking the sample and equipment. Particular attention is paid to the surface of the part.
Selection of permissible force.
Installation of the test material.
Putting the hardness tester into operation.
Reading the result on the dial.

The mathematical calculation for this method is as follows:

HV=1.8544*(F/d2),

where F – load, kgf; d – average value of the print diagonal lengths, mm.

It allows you to measure high hardness of metals, thin and small parts, while providing highly accurate results.

Ways to switch between scales

Having determined the diameter of the print using special equipment, you can use tables to determine the hardness. The metal hardness table is a proven assistant in calculating this mechanical parameter. Thus, if the Brinell value is known, the corresponding Vickers or Rockwell number can be easily determined.

Example of some match values:

Print diameter, mm	Research method
Brinell	Rockwell	Vickers
A	C	B
3,90	241	62,8	24,0	99,8	242
4,09	218	60,8	20,3	96,7	218
4,20	206	59,6	17,9	94,6	206
4,99	143	49,8	—	77,6	143

The metal hardness table is compiled on the basis of experimental data and is highly accurate. There are also graphical dependences of Brinell hardness on the carbon content in an iron-carbon alloy. So, in accordance with such dependencies, for steel with an amount of carbon in the composition equal to 0.2%, it is 130 HB.

Sample requirements

In accordance with the requirements of GOSTs, the tested parts must meet the following characteristics:

The workpiece must be flat, lie firmly on the hardness tester table, its edges must be smooth or carefully processed.
The surface should have minimal roughness. Must be sanded and cleaned, including using chemical compounds. At the same time, during machining processes, it is important to prevent the formation of work hardening and an increase in the temperature of the treated layer.
The part must comply with the selected method for determining hardness using parametric properties.

Fulfillment of primary requirements is a prerequisite for measurement accuracy.

The hardness of metals is an important fundamental mechanical property that determines some of their other mechanical and technological features, the results of previous processing processes, the influence of temporary factors, and possible operating conditions. The choice of research methodology depends on the approximate characteristics of the sample, its parameters and chemical composition.

Source: https://FB.ru/article/269317/tverdost-metallov-tablitsa-tverdosti-metallov

Difference between aluminum and steel

Metals are chemical elements that have characteristic properties such as ductility, malleability, and electrical conductivity. Most elements in the periodic table are metals. One of the main uses of metals is in the production of metal alloys such as steel. The main difference between aluminum and steel is that aluminum is a metal while Steel is a metal alloy.

Key areas covered

1. What is Aluminum
- Manufacturing, Properties, Uses
2. What is Steel
- Types, Components, Properties, Uses
3. What is the Difference Between Aluminum and Steel
- Comparison of Key Differences

Key terms: aluminum, ductility, ductility, metal, metal alloy, stainless steel, steel

What is aluminum

Aluminum (Al) is a soft metal with a silver-gray color. Has a shiny appearance Aluminum is lightweight compared to other metals. It is malleable, meaning it can deform under pressure. These properties of aluminum made it suitable for use in aircraft construction.

Aluminum is highly resistant to corrosion because it can form a protective layer on its surface by oxidizing into aluminum oxide. In addition, it is a good conductor of heat and electricity. The degree of ductility is high for aluminum; this means that aluminum can be easily melted and drawn into wire structures. Aluminum foil is impenetrable, even if it is very thin.

Aluminum metal is produced from aluminum oxide (alumina). The process of refining aluminum from alumina is known as the Hall-Herult process. The process includes the following steps.

Dissolution of alumina in molten cryolite.
Separation of alumina into its elements by electrolysis.

Pattern: aluminum cube

What is steel

Steel is a metal alloy consisting of iron, carbon and several other elements such as manganese, tungsten, phosphorus and sulfur. The percentage of carbon in steel can vary. Based on the amount of carbon present, steel can be divided into several groups, such as:

Mild steel
High carbon steel
Low carbon steel

THIS IS INTERESTING: Where do aluminum come from?

Sometimes steel has some other elements in high percentages than carbon. A good example of this is stainless steel. Stainless steel contains very little carbon, but along with iron it contains a lot of chromium. Various desired properties can be obtained by mixing various metallic and non-metallic elements with iron in varying quantities. Types of steel according to the different elements present;

Carbon Steel - Main Components - Iron and Carbon
Alloy steel - the main components are iron, carbon and manganese
Stainless steel - iron and chromium with a small amount of carbon
Tool steel - tungsten, molybdenum-like metals are present with iron

Steel is hard, very durable and ductile. But it is not resistant to corrosion (except for stainless steel, which is made by mixing chromium with iron to impart corrosion-resistant properties). Steel corrodes easily when exposed to a humid environment. That's why rust occurs.

Figure 2: Rust of steel

Definition

Aluminum: Aluminum is a soft metal with a silvery gray color.

Steel: Steel is a metal alloy consisting of iron, carbon and several other elements.

Corrosion resistance

Aluminum: Aluminum is resistant to rust and corrosion.

Steel: Steel is not resistant to corrosion and rust occurs easily.

density

Aluminum: Aluminum is a soft metal with a relatively low density.

Steel: Steel is a high density carbide alloy.

Weight

Aluminum: Aluminum is a lightweight metal.

Steel: Steel has more weight than aluminum.

weldability

Aluminum: Aluminum is difficult to weld.

Steel: Steel is easy to weld.

Melting temperature

Aluminum: Aluminum has a lower melting point.

Steel: Steel has a very high melting point.

Conclusion

Metals and metal alloys have many uses on an industrial scale. Aluminum and steel are such elements. The main difference between aluminum and steel is that aluminum is a metal while steel is a metal alloy.

Recommendations:

1. “What is aluminum?” Our business | Bauxite Resources Limited. N.p., n.d. Web.

Source: https://ru.strephonsays.com/difference-between-aluminium-and-steel

The effect of temperature on aluminum – Ecobalance

Al (from Latin aluminium) , a chemical element of the IIIA subgroup of the periodic table of elements (B, Al, Ga, In, Tl), the most common metal in the earth's crust, is found in a large number of minerals, such as clay and granite.

Aluminum production

The main raw material for aluminum production is bauxite, an ore that is mainly hydrated aluminum oxide Al2O3Х2H2O. The world leader in aluminum production is the USA, followed by Russia, Canada and Australia. Aluminum is best known as a raw material for the production of alloys used for the manufacture of food containers (cans, cylinders, cans, etc.

), light kitchenware and other household utensils. Crude aluminum was first isolated by H. Oersted in 1825, although back in 1807 H. Davy discovered an unknown metal when treating clay with sulfuric acid. Davy was unable to isolate the metal from the compounds, but called it aluminum (from lat.

alumen - alum), and its oxide - alumina (alimina); soon this name of the metal, by analogy with the names of other metals, was changed to “aluminum”, which became generally accepted.

Properties of aluminum

A remarkable property of aluminum is its lightness; The density of aluminum is approximately three times less than that of steel, copper or zinc. Pure aluminum is a soft metal, but forms alloys with other elements to provide a wide range of useful properties. In terms of thermal conductivity and electrical conductivity, aluminum ranks after silver and copper.

Aluminum is highly reactive, so it does not occur in nature in a free state. Metallic aluminum dissolves quickly in hydrochloric acid to form AlCl3 chloride, and more slowly in sulfuric acid to form Al2(SO4)3 sulfate, but it reacts with nitric acid only in the presence of mercury salts.

In reaction with alkalis it forms aluminates, for example, with NaOH it forms NaAlO2. Aluminum exhibits amphoteric properties, as it reacts with both acids and alkalis. In air, aluminum is quickly covered with a durable protective film of Al2O3 oxide, protecting it from further oxidation.

Therefore, aluminum is stable in air and in the presence of moisture, even with moderate heating. If the protective film of the oxide is broken, then when heated in air or oxygen it burns with a bright white flame. When heated, aluminum reacts actively with halogens, sulfur, carbon and nitrogen. Molten aluminum reacts explosively with water.

PROPERTIES OF ALUMINUM

Atomic number 13
Atomic mass 26.9815
Isotopes stable 27, unstable 24, 25, 26, 28, 29
Melting point, ° C 660
Boiling point, °C 2467
Density, g/cm3 2.7
Hardness (Mohs) 2.0-2.9
in the earth's crust, % (wt.) 8.13
Oxidation states +3

Application of aluminum

Since ancient times, alum has been used in medicine as an astringent, in dyeing for mordant, and for tanning leather. Alum is often called mixed sulfates of mono- and trivalent metals, such as aluminum and potassium (the mineral solvaterite). The Roman scientist Pliny the Elder (1st century AD) in his Natural History mentions alum as a salt whose properties were studied by alchemists.

The Egyptians were the first to use alum for tanning leather and for medicinal purposes; they, as well as the Lydians, Phoenicians and Jews, knew that some dyes, such as indigo and cochineal, were better preserved if they were mixed or soaked in alum. Crystalline aluminum oxide, found naturally as corundum, is used as an abrasive due to its high hardness.

Ruby and sapphire are varieties of corundum colored with impurities and are gemstones.

Applications of aluminum metal

Aluminum is one of the lightest structural metals. Alloys obtained from aluminum after heat treatment, along with low density, are distinguished by high strength and other important mechanical properties, which makes aluminum indispensable for the manufacture of vehicle parts (pistons and crankcases, blocks and cylinder heads of aircraft and automobile engines, bearings, power trains and casing fuselages, etc.).

Aluminum is easily drawn and drawn, which is used in the production of food containers. The electrical conductivity of aluminum is approx. 61% of the electrical conductivity of copper, but aluminum is three times less dense.

The combination of good conductivity with high corrosion resistance in air expands the use of aluminum cables, often reinforced with steel, for high-voltage power transmission. Aluminum is also distinguished by its high thermal conductivity, which is used in engines, cooling systems and other devices.

Source: http://ekobalans.ru/harmful-substances/vliyanie-temperaturyi-na-alyuminiy

How to determine aluminum at home - Metalist's Handbook

We welcome everyone who, being a real owner, draws knowledge and experience from our site. This suggests that today for some reason you are interested in the question of how to distinguish aluminum from stainless steel. But really, it’s not that simple.

Features of aluminum

Why is aluminum so valuable? This is a pure metal classified as non-ferrous. It is lightweight, durable, has a good degree of deformation, and is resistant to aggressive environments and corrosion.

All of the listed advantages allow it to be used in a variety of areas from industry and construction (except for industries where high-strength structures are manufactured) to domestic use.

The demand for the valuable metal is great, so it is important to know how to accurately distinguish it from other similar metal alloys.

There are several ways to help you do simple research on your own at home. Find out how to distinguish aluminum from stainless steel - advice from forum members and experts.

Using a magnet. Aluminum of any grade will not stick to a magnet. Stainless steel also has this property. But there is an exception to the rule. If it contains nickel in sufficient quantities, the tested products will have some attraction. If there is a lot of chromium or copper in a stainless metal, it will not have any effect on the magnet.
Marking on stainless steel. Some stainless steel products have identification markings. This already gives a hint on how to distinguish aluminum from stainless steel. If there are markings, for example, “STAINLESS” and the like, this is not aluminum.
Plain paper won't lie. The method is very simple. Experiment conditions: you need white, as thick paper as possible (printer paper will also work). Use a thick cloth to remove dirt from the edges of the products being tested. Move the cleaned areas one by one with some pressure across the sheet. There will be no traces left of the stainless steel. Aluminum will draw gray stripes.
How to distinguish aluminum from stainless steel by the color of the metal? The surface of the object has a shiny, colorless hue that does not change over time - it is stainless steel. The matte surface of a product that has a grayish or whitish color is aluminum. It will not be polished with sandpaper to a high gloss finish. Check it out.
Under mechanical load. Another simple way will help you understand how to distinguish aluminum from stainless steel. Hit the product against the surface of any hard metal in the dark. Aluminum will never spark, unlike stainless steel.
Thermal conductivity, melting. Compare where the water heats up faster. Of course, in an aluminum container. This metal has much better thermal conductivity. But it is not used on the burner of a gas furnace; the melting point is 660 °C. Stainless steel cannot be melted in the usual way (melting index is above 1800 °C).
Testing for copper sulfate. An option available to everyone. Copper sulfate, after exposure to aluminum, will leave cloudy stains and traces on it, but will not appear on stainless steel.
Alkaline solutions. Any housewife knows that it is impossible to boil aluminum cookware in alkaline solutions. It will darken and lose its appearance. Conclusion: aluminum products are afraid of alkali, both sodium and potassium. The same cannot be said about stainless steel.
Acid test. All acids, starting with the usual citric acid and ending with more aggressive ones, will leave marks when they get on the aluminum surface. You won’t see them on stainless steel; it doesn’t react with acids.

Duralumin – an alloy of aluminum with transition metals

The industry is not able to provide itself only with pure metal, and duralumin comes to the rescue here - various combinations of manganese, copper and magnesium in an alloy with aluminum.

In addition to all the above properties of its older brother, the transition metal has:

high degree of strength;
long service life;
plasticity;
high hardness.

It accumulates fatigue properties more slowly and is resistant to cracking.

The disadvantage of products made of duralumin is susceptibility to corrosion, which can be prevented by anodizing, applying a thin layer of paints and varnishes, aluminum.

The choice between the two metals depends on the end use. We pay tribute to their advantages, but also foresee their disadvantages. The domestic sector leaves the choice to aluminum, while the industrial sector votes for the strength that duralumin has.

Naturally, the question arises of how to distinguish aluminum from duralumin. It is almost impossible to determine by eye which metal is which. The chemical laboratory will give you the exact answer. But experts on the forums have their own opinion on this matter.

Follow the markings.
The color of the alloy is steel gray.
Scratches leave clear marks.
A ringing sound is heard from the impact.
During processing, the chips will break without ductility.
The structure of the alloy is fine-crystalline.

You can determine the type of material by conducting an experiment. Apply a drop of sodium hydroxide to duralumin and aluminum samples for 10 minutes. After removing the substance, we learn about the metal from the resulting stains: the dark one is duralumin.

If you place a piece of aluminum in an acid with added alkali, it will dissolve, forming a white powdery precipitate. In the experiment with duralumin, blue copper granules will be present.

Unlike aluminum, the main characteristics of the alloy are lack of ductility, brittleness and hardness.

Everything can be learned by comparison; examine the parts of two samples several times, pick them up and compare the weight. Such familiarity will help you subsequently simply recognize metals.

Silumin - a twofold relationship

Products made from silumin, an aluminum-based alloy with the addition of silicon, literally flooded the market. Why does it attract the buyer and how to distinguish aluminum from silumin?

Advantages of silumin

Of course, this alloy of two materials has its “fans”. They call the following positive features of silumin:

light in weight;
highly durable;
resistant to wear and corrosion;
cheap price.

Cons of silumin

Silumin products should be treated with caution, unlike aluminum ones. in silumin, aluminum production waste, silumin-containing alloys, and metal powder do not have an exact proportion. It cannot be called high quality, since the manufacturer produces cheap products under the name of some brand.

The disadvantages of the alloy include:

design flaws;
they are unsuitable for food products;
dangerous to health.

You can distinguish silumin from aluminum visually. The products have a glossy smooth gray surface.

Today, public dissatisfaction with plumbing products continues to grow due to the heterogeneous structure of the material with numerous internal stresses and voids. After 3-5 months, the water tap turns into dust, and the rotary steel ball rusts.

When replacing heating radiators, many are faced with the choice of which material to choose for the new design. Cast iron batteries are a thing of the past; manufacturers offer aluminum, steel and bimetallic ones. While steel is easily recognizable in appearance, the problem with aluminum and bimetallic structures is that you can’t tell the difference by eye. Moreover, the latter option is in greatest demand. In the store there is a chance not to buy a fake, but how to distinguish bimetal from aluminum at the market?

Visual recognition will not provide accurate results to the consumer. Both the aluminum and bimetallic systems have external fins made of aluminum. And it’s impossible to visually determine the weight of one section.

For reference: the aluminum section weighs 1–1.6 kg, the bimetallic radiator “compartment” weighs 1.5–2 kg.

You can use the “old-fashioned” method and arm yourself with a neodymium magnet, which has greater power.

Preliminary test. Place the magnet first on the steel, then on the aluminum radiator. The magnetic tester will attract the first option to the surface. The effect will be weaker for a bimetallic radiator. Its steel tubes are located under a diamagnetic material - aluminum. With a powerful neodymium magnet, it is possible to catch the attraction.

It is more difficult when the coolant tubes are made of copper, which, like aluminum, is impervious to the magnetic field.

Difference from other non-ferrous metals

It is known that metals have largely identical properties. But each element has its own distinctive characteristics. They allow you to understand how to distinguish metal from aluminum:

copper is recognized by its bright reddish hue;
iron and its alloys have high magnetic properties;
You can recognize gold by its yellow color;
Lead has high fragility and density;
silver has a bright shine;
Tin has high ductility.

The above methods are only estimates and approximate. More reliable information is available on the pages of special reference literature.

Source: https://ssk2121.com/kak-opredelit-alyuminiy-v-domashnih-usloviyah/