Alloy name composition properties application table

Alloy classification

There are several ways to classify alloys:

• by manufacturing method (cast and powder alloys);
• by the method of obtaining the product (casting, wrought and powder alloys);
• by composition (homogeneous and heterogeneous alloys);
• according to the nature of the metal - base (ferrous - Fe base, non-ferrous - base, non-ferrous metals and alloys of rare metals - radioactive elements base);
• by the number of components (double, triple, etc.);
• by characteristic properties (refractory, low-melting, high-strength, heat-resistant, hard, anti-friction, corrosion-resistant, etc.);
• by purpose (structural, instrumental and special).

About metals and alloys

Hello, friends! Today I propose to consider some metals and their alloys . In this article we will try to cover all the possibilities and characteristics of metals and highlight their main advantages and qualities.

Metals and alloys

The most common types of metals and alloys are: - copper , bronze, brass, aluminum, zinc, lead, tin, chromium, nickel, nickel silver and cupronickel.

Light alloys

For crafts, pure copper (that is, red) or various light alloys are usually used.

Red copper is especially suitable for coining; it is very malleable and can be easily processed with various chemicals. substances to obtain different shades of color. In addition, it is perfectly ground and polished, and is characterized by high resistance to corrosion.

The disadvantage of red copper is its poor weldability (special electrodes for welding are required) and rapid oxidation in open air masses, which is why its original shine is lost.

Copper blanks (rods)

Bronze is obtained by fusing tin with copper. Workpieces made from it are harder and more durable than copper itself. Bronze is excellent for casting and forging. You are unlikely to find a ready-made bronze alloy on sale. Therefore, craftsmen often produce it themselves.

Bronze and brass sheets in rolls

Brass is an alloy of copper and zinc. In blacksmithing, it is used with individual alloying elements: aluminum, nickel, lead, etc.

Brass polishes and cuts better than red copper. It is beautifully plated with gold, silver, and nickel. But brass is inferior in ductility to copper.

Aluminum is a lightweight, soft metal with a light silver color. Its density is three times lower than that of steel. Aluminum, and in particular its alloys (high-strength structural, technical deformed, duralumin, etc.), which are widely used in light industry, are perfectly processed under normal conditions.

Zinc has a silvery-blue tint. When exposed to oxygen, it becomes covered with a matte film, which protects the metal from corrosion. Zinc is very useful for protecting various ferrous metals from corrosion, and this is where it is most often used (the so-called “galvanizing” - for example, the well-known drainpipes, galvanized metal of cars, etc.).

Zinc in ingots

Lead is soft, ductile and at the same time a heavy metal. Resistant to acids. Typically used for the production of low-melting solders and in the electrochemical industry.

Tin is a ductile and soft metal with a light silver color. Used to form anti-corrosion coatings. It is resistant to food acids and is therefore widely used in the manufacture of lids, cans, etc.

Chrome is a light blue metal. It has excellent anti-corrosion properties and high hardness. The efficiency of products made of steel or cast iron coated with chrome increases significantly.

Nickel is a light silvery metal. But unlike chrome, it has a delicate yellowish tint. More resistant to aggressive environments. Like chromium, it is widely used to protect decorative metal coatings - the so-called nickel plating.

Nickel silver and cupronickel are formed by alloying copper and nickel. The presence of copper in them is quite high - 82% and 66%, respectively. Because of this, they have good ductility.

When processed with lead acetic acid and sodium hyposulfate, different shades are produced. The surfaces of these metals are highly polished and have a number of other important features.

This concludes the article about metals and their alloys.

In the future, I propose to also consider the properties and structure of wood. Until next time.

[1 Average: 5] “I live in the city of Shatura, Moscow region. Since childhood, he was “turned” to construction. Mastered many professions, incl. carpenter-concrete worker, mason-builder, furniture maker. I share my experience on this blog.”

Properties of alloys

The properties of alloys depend on their structure. Alloys are characterized by structure-insensitive (determined by the nature and concentration of the elements that make up the alloys) and structure-sensitive properties (depending on the characteristics of the base). The structurally insensitive properties of alloys include density, melting point, and heat of evaporation. thermal and elastic properties, coefficient of thermal expansion.

All alloys exhibit properties characteristic of metals: metallic luster, electrical and thermal conductivity, ductility, etc.

Also, all the properties characteristic of alloys can be divided into chemical (the relationship of alloys to the effects of active media - water, air, acids, etc.) and mechanical (the relationship of alloys to the effects of external forces). If the chemical properties of alloys are determined by placing the alloy in an aggressive environment, then special tests are used to determine the mechanical properties. So, to determine strength, hardness, elasticity, ductility and other mechanical properties, tensile, creep, impact strength, etc. tests are carried out.

Educational materials

Pure metals find rather limited use as structural materials. The main structural materials are alloys. They have more valuable complexes of mechanical, physical and technological properties than pure metals.

An alloy is a substance obtained by fusing two or more elements (components).

An alloy made primarily from metallic elements and having metallic properties is called a metal alloy. Metal alloys can also be produced by powder metallurgy (sintering), diffusion, and the deposition of several elements on the cathode during electrolysis of aqueous solutions.

The basic concepts in the theory of alloys include system, component, phase.

A system is a group of bodies allocated for observation and study. In metallurgy, systems are metals and metal alloys.

Components are the substances that form a system, taken in the smallest quantities. In metal alloys, the components can be elements (metals and non-metals) and chemical compounds (which do not dissociate when heated). Pure components are designated by capital letters of the Latin alphabet A, B, C, D.

A phase is a homogeneous part of a system, separated from another part of the system by an interface, during the transition through which the composition, structure and properties change abruptly.

Alloys can be single-phase, two-phase, three-phase.

Depending on the physicochemical interaction of the components, the following phases can be formed: liquid solutions, solid solutions and chemical compounds.

Almost all metals in the liquid state dissolve in each other in any ratio. As a result, a homogeneous liquid solution is formed with a uniform distribution of atoms of one metal among the atoms of another metal.

Solid solutions are phases in which one of the components of the alloy retains its crystal lattice, and the atoms of other (or other) components are located in the lattice of the first component (solvent), changing its dimensions.

Thus, a solid solution consisting of two or more components has one type of lattice and represents one phase.

Depending on the nature of the distribution of element atoms, interstitial, substitutional and subtractive solid solutions are distinguished.

In interstitial solid solutions, the atoms of the soluble element are distributed in the crystal lattice of the solvent metal, occupying spaces between its atoms. Only atoms with very small sizes can fit into such voids. Some metalloids and hydrogen, nitrogen, carbon, and boron have the smallest atomic sizes, which form interstitial solid solutions with metals.

In solid solutions of substitution, atoms of the soluble element take the place of atoms of the base metal. Foreign atoms can replace solvent atoms in any place, therefore such solutions are called disordered solid solutions.

Substitutional solid solutions can have limited or unlimited solubility. Thus, up to 5.5% copper can be dissolved in aluminum, and up to 39% zinc can be dissolved in copper. For example, the components of the systems: Cu-Ni, Cu-Au, Ag-Au, Cu-Pt, Fe-Cr, Fe-Ni have unlimited solubility. For the formation of solid solutions of unlimited solubility, the following conditions must be met: the components must have the same type of crystal lattices; the difference in the atomic sizes of the components should be insignificant and not exceed 8...15% (for example, Ag and Cu - DR = 0.2%, Cu and Ni - DR = 2.7%); the components must belong to the same group of the periodic system or an adjacent related group and have a similar structure of the valence shell of electrons in the atoms.

In some alloys, as the temperature in substitutional solid solutions decreases, a process of redistribution of atoms may occur, as a result of which the atoms of the dissolved element will occupy strictly defined positions in the solvent lattice. Such solid solutions are called ordered, and their structure is called a superstructure. The temperature of transition to an ordered state is called the “Kurnakov point”. Completely ordered solutions are formed when the ratio of components in the alloy is equal to a whole number: 1:1, 1:2, 1:3, etc. In this case, the alloy can be assigned the formula of a chemical compound, for example, CuAu, Cu3Au. They can be considered as intermediate phases between solid solutions and chemical compounds. Unlike a chemical compound, the lattice of the solvent is preserved, and when heated above the Kurnakov point, the degree of ordering gradually decreases and they become disordered. Ordered solid solutions are characterized by greater hardness, strength, lower ductility and electrical resistance.

Subtraction solid solutions are formed on the basis of certain chemical compounds when one of the elements included in its formula is added to this chemical compound. The atoms of this element occupy normal positions in the lattice of the compound, and the places where the atoms of the second component should be located turn out to be unfilled and empty. Such solid solutions are formed, for example, when the chemical compound NiAl is fused with Al, titanium carbide TiC with Ti, when FeO dissolves oxygen.

Solid solutions are usually denoted by lowercase letters of the Greek alphabet a, b, g, d.

Chemical compounds and phases related to them by nature in metal alloys are diverse. They are usually formed by elements that have large differences in the electronic structure of their atoms and crystal lattices.

Characteristic features of chemical compounds:

1. the crystal lattice is different from the lattices of the components that form the compound;
2. a simple multiple ratio of components is maintained in the form of AnBm;
3. the properties of the compound differ sharply from the properties of the components that form it;
4. the melting (dissociation) temperature is constant.

The formation of a chemical compound is accompanied by a significant thermal effect.

Compounds of one metal with another are called intermetallic compounds. The bond between atoms in intermetallic compounds is often metallic. An example is the compounds Mg2Sn, Mg2Pb.

When a chemical compound of a metal and a non-metal is formed, an ionic bond occurs, for example, in the NaCl compound.

Transition metals (Fe, Mn, Cr, Mo, W, V, etc.) form carbides with carbon, nitrides with nitrogen, borides with boron, hydrides with hydrogen (iron does not form hydrides) They have a common structure and properties and are called interstitial phases . They have the formulas: MX (WC, VC, TiC, NbC, TiN, VN, etc.); M2X (W2C, Mo2C, Fe2N, etc.); M4 X (Fe4N, Mn4N, etc.).

The crystal structure of interstitial phases is determined by the ratio of the atomic radii of the nonmetal (Rx) and metal (Rm). If Rx/Rm < 0.59, then the metal atoms in these phases are arranged like one of the simple crystal lattices: cubic (K8, K12) or hexagonal (G12), into which non-metal atoms are embedded, occupying certain pores in it.

If this condition is not met, as is observed for iron, manganese and chromium carbide, then compounds with more complex lattices are formed, and such compounds cannot be considered interstitial phases.

Many interstitial phases have high strength and hardness and are often used in steels to obtain increased strength (precipitation hardening steels).

In addition, chemical compounds include electronic compounds and Laves phases (AB2), for example, MgZn2, MgCu2, CaAl2.

Electronic compounds are most often formed between monovalent (Cu, Ag, Au, Li, Na) metals or transition group metals (Fe, Mn, Co, etc.) on the one hand and simple ones with a valency from 2 to 5 (Be, Mg, Zn, Cd, Al, etc.).

State diagram for alloys forming mechanical mixtures of pure components (type I) > Continue >

Main types of alloys

Various steels, cast iron, alloys based on copper, lead, aluminum, magnesium, as well as light alloys are widely used among all kinds of alloys.

Steels and cast irons are alloys of iron and carbon, with the carbon content in steel up to 2%, and in cast iron 2-4%. Steels and cast irons contain alloying additives: steels – Cr, V, Ni, and cast iron – Si.

There are different types of steels; for example, structural, stainless, tool, heat-resistant and cryogenic steels are distinguished according to their intended purpose. Based on their chemical composition, they are divided into carbon (low-, medium- and high-carbon) and alloyed (low-, medium- and high-alloy). Depending on the structure, austenitic, ferritic, martensitic, pearlitic and bainitic steels are distinguished.

Steels have found application in many sectors of the national economy, such as construction, chemical, petrochemical, environmental protection, transport energy and other industries.

Depending on the form of carbon content in cast iron - cementite or graphite, as well as their quantity, several types of cast iron are distinguished: white (light color of the fracture due to the presence of carbon in the form of cementite), gray (gray color of the fracture due to the presence of carbon in the form of graphite ), malleable and heat resistant. Cast irons are very brittle alloys.

Read also: Stiffness coefficient for series connection of springs

The areas of application of cast iron are extensive - artistic decorations (fences, gates), cabinet parts, plumbing equipment, household items (frying pans) are made from cast iron, and it is used in the automotive industry.

Copper-based alloys are called brasses; they contain from 5 to 45% zinc as additives. Brass containing 5 to 20% zinc is called red (tompak), and brass containing 20–36% Zn is called yellow (alpha brass).

Among lead-based alloys, two-component (lead alloys with tin or antimony) and four-component alloys (lead alloys with cadmium, tin and bismuth, lead alloys with tin, antimony and arsenic) are distinguished, and (typical of two-component alloys) with different contents of the same components different alloys are obtained. Thus, an alloy containing 1/3 lead and 2/3 tin - tertiary (ordinary solder) is used for soldering pipes and electrical wires, and an alloy containing 10-15% lead and 85-90% tin - pewter, was previously used for casting cutlery.

Aluminum-based two-component alloys – Al-Si, Al-Mg, Al-Cu. These alloys are easy to produce and process. They have electrical and thermal conductivity, are non-magnetic, harmless in contact with food, and explosion-proof. Aluminum-based alloys are used for the manufacture of lightweight pistons; they are used in carriage, automobile and aircraft construction, the food industry, as architectural and finishing materials, in the production of technological and household cable ducts, and in the laying of high-voltage power lines.

Alloys. Types, characteristics of alloys

Due to their low mechanical properties, pure metals as structural materials in mechanical engineering are of limited use compared to alloys.

An alloy is a structural material obtained by fusing several chemical elements (metals and non-metals) and possessing properties inherent in the main element being alloyed.

A metal alloy can be obtained not only by fusion of chemical elements, but also by such methods as sintering, electrolysis, diffusion, plasma spraying, sublimation, etc. A structural material not obtained by fusion is called a pseudo-alloy. If an alloy contains 50% metal or more, then it is called a metal alloy.

A metal alloy has higher mechanical and technological properties compared to a non-metal alloy. The chemical elements that form an alloy are called components.

In terms of their composition, alloys can be two-component (metal + metal, metal + non-metal), three-component or more. The internal structure of alloys is determined by the form of bonding between the components.

Two-component alloys, when heated (cooled), due to the peculiarities of their interaction with each other, behave inadequately and, therefore, have different physical structures and properties.

Industrial alloys that are widely used include:

• cast iron and steel are alloys of iron and carbon;
• brass - an alloy of copper and zinc;
• bronze - an alloy of copper and tin, etc.

Alloys have an atomic-crystalline structure, have allotropy (polymorphism) and, in comparison with pure metals, higher mechanical and technological properties.

The form of the metallic bond of the chemical elements being fused affects the formation of the alloy structure and their atomic-crystalline lattice.

Phases. Alloys, like pure metals, are characterized by an atomic-crystalline structure. An alloy in the solid state may have a different connection of atomic-crystal lattices. The liquid or solid state of chemical components that form an alloy at a certain temperature and pressure is called a system.

The homogeneous part of the system, separated from other parts by a conventional boundary (line), is called a phase.

The liquid phase is characterized by the fact that the atomic crystal lattices of the alloyed components disintegrate and the components dissolve in each other or do not dissolve and are present in the alloy independently. This pattern is inherent in many alloys.

The solid phase is a homogeneous part of the alloy with a certain atomic-crystalline structure and mass fraction of alloyed components. The atomic lattices of the fused components interact in a strictly defined order. The atomic lattices of the chemical elements that form the alloy in the solid state form small crystals - structures.

Depending on the internal structure of the alloys and the metallic or chemical bond between the alloyed elements, alloys are divided into two groups:

• homogeneous alloys;
• heterogeneous alloys.

Homogeneous alloys have common atomic crystal lattices, which include atoms of the alloyed components.

Inhomogeneous alloys have independent crystal lattices of alloyed components.

Based on the nature of the interaction of the fused components in the solid phase, mechanical mixtures, solid solutions and chemical compounds are distinguished.

A mechanical mixture of fused components A and B (Fig. 1, a) is formed when the atomic crystal lattices are preserved and do not enter into a chemical reaction to form any new compound. The connection between atomic lattices is carried out due to metallic bonds. The mechanical mixture of the alloy will be of a heterogeneous type, that is, the alloyed components A and B in the alloy will be independent and alternate with each other depending on their ratio.

Rice. 1. Schematic representation of the alloy structure: a - mechanical mixture; b - solid solution (I - substitution solution; II - interstitial solution); c - chemical compound; A, B - fused components

The properties of the mechanical mixture depend on the properties of the fused components A and B. As a rule, these microstructures have relatively high hardness, strength, impact strength, and are well processed by cutting.

Solid solutions , depending on the interaction of atoms, are divided into interstitial solid solutions and substitutional solid solutions (Fig. 1, b).

In Fig. 1, b, I shows the atomic crystal lattice of a substitutional solid solution. The atomic-crystal lattice of the main component A in the form of a body-centered cube (nine atoms) is preserved, but three atoms of this component are replaced by atoms of the fused component B.

In Fig. Figure 1, b, II shows the atomic crystal lattice of the interstitial solid solution. With this type of alloy formation, the atomic crystal lattice of the main component A is preserved. The atomic-crystal lattice of the alloyed component B is destroyed, and its individual atoms are introduced into the space of the atomic-crystal lattice of the main component A. Thus, in the atomic-crystal lattice of the interstitial solid solution there are nine atoms, as in the main component A, plus two or three atoms of the component B.

Solid solutions in their properties are closest to the properties of the main component. They have low hardness, high density, impact strength, strength, and are easily deformed in cold and hot conditions. The microstructure of most structural and tool steels is interstitial and substitutional solid solutions.

Chemical compounds of the alloy are formed when the atomic crystal lattices of the alloyed components A and B disintegrate. Individual atoms of these components form new atomic lattices, which in their type, shape and number of atoms differ from the atomic crystal lattices of the fused components.

Chemical compounds in the alloy are formed at a strictly defined mass ratio of the alloyed components A and B. For example, a chemical compound of carbon with iron is formed at a mass fraction of carbon equal to 6.67%.

The properties of chemical compounds also differ sharply from the properties of the fused components. Chemical compounds are usually very hard, brittle, refractory, and have a fine-grained or needle-like microstructure. In Fig. 1, c shows an atomic-crystalline cell of a chemical compound of carbon with iron. This is a complex rhombic spatial atomic-crystal lattice, consisting of iron atoms and carbon atoms (components A and B).

In practice, most often a mixture of several compounds (microstructures) is observed in an alloy, for example, a mechanical mixture of a chemical compound and a solid solution or a mechanical mixture of two solid solutions.

State diagrams of two-component alloys. Any change in the chemical composition of the alloy entails a change in physical parameters: temperature, pressure and structure. The change in these parameters at phase boundaries occurs abruptly or slowly.

In the practice of metallurgy, graphs - state diagrams of alloys - are used to determine temperatures, pressure, structure and interaction of alloyed components. To do this, the alloy is heated (cooled) in a closed crucible using a thermocouple, the behavior of this alloy is observed using the device, and corresponding graphs are drawn from the observations.

Phase diagrams display only conditions when the alloy has constant parameters - equilibrium, therefore in the scientific literature, phase diagrams are also called equilibrium diagrams. Due to the fact that the alloyed components (metals and non-metals) have allotropy, when heated (cooled) allotropic changes occur in the alloys. Allotropic changes can be observed in laboratory studies using the thermal method, and sometimes visually (the color of the alloy becomes brighter or, conversely, dims, or remains constant for a long time).

Any change in a metal during heating (cooling) is characterized by a certain temperature, which is called the critical temperature. Critical temperatures on a straight line are reflected by corresponding points, which are called critical points. If we consider any metal or alloy in one dimension (heating temperature), then the graphical characteristic will be displayed in the form of a vertical line on which critical temperatures (points) are indicated. If the state of a metal or alloy is considered in two dimensions (heating (cooling) temperature and heating (cooling) time), then the graph will be depicted in two coordinates (ordinate axis and abscissa axis).

For example, consider the state of pure iron when heated and cooled. In Fig. Figure 2 shows the critical temperatures of pure iron when heating (cooling). Iron has the following critical points (temperatures): 768; 910; 1,392 and 1,539 °C. At a temperature of 910 °C, Fe-α (α-iron) transforms into Fe-β (β-iron). At a temperature of 1,392 °C, Fe-β transforms into Fe-γ (γ-iron). At a temperature of 1539 °C, Fe-γ begins to slowly melt with the absorption of energy (temperature).

At all critical temperatures, the diagrams show recrystallization delays (horizontal sections). When iron cools, the recrystallization process occurs in the reverse order.

For two-component alloys, a phase diagram is a graphical representation of the state of the alloys in two dimensions: heating (cooling) temperature and chemical composition of the alloy (concentration).

Rice. 2. Iron heating and cooling curves: t - temperature; τ — time

The heating (cooling) temperature is plotted along the ordinate axis, and the mass fraction of the fused components (concentration) is plotted along the abscissa axis.

For example, consider the phase diagram of a two-component lead-antimony alloy (Fig. 3). On the x-axis we take 100% lead (Pb) on the left, and 100% antimony (Sb) on the right. Lead and antimony in the liquid state dissolve indefinitely in each other, in the solid state they form a mechanical mixture of fused components.

When an alloy is heated (cooled) from the solid state to the melting temperature (and when cooled from the liquid state to the solidification temperature), the formation of mechanical mixtures (eutectic) and melting at different temperatures occurs in the alloy.

Let's take pure lead. At normal temperatures and up to a temperature of 245 ° C, no changes in the internal structure occur in lead, and the lead will have the structure Pb-α (α-lead). At a temperature of 245 °C, Pb-α is transformed into Pb-β (β-lead). This structure remains up to a temperature of 327 °C.

At a temperature of 327 °C, lead begins to melt. When melting due to the absorption of energy (temperature), the temperature of the lead remains constant - 327 ° C. When cooling lead, the process occurs in the reverse order.

Rice. 3. Cooling curves and structures (a, b, c, e, f), state diagram (d) of lead-antimony alloys: 1 - liquidus temperature; 2—solidus temperature; ABC - liquidus line; DBE—solidus line; F - liquid; Eut. - eutectic

When antimony is heated to a temperature of 245 °C, no changes occur in the metal. The structure of antimony will be Sb-α (α-antimony). At a temperature of 245 °C, Sb-α transforms into Sb-β. At a temperature of 631°C, antimony begins to melt. Due to the fact that during melting there is a large absorption of heat, the melting temperature of antimony will be 8 ... 10 ° C lower. When cooling, the process occurs in the reverse order. Next, we consider the behavior of typical lead and antimony alloys: 95% Pb + 5% Sb; 87% Pb + 13% Sb; 60% Pb + 40% Sb. To draw a state diagram of a two-component lead-antimony alloy, we construct heating (cooling) curves.

When heating (cooling) 100% Pb (Fig. 3, a) at a temperature of 327 °C, there will be a horizontal section on the graph. When heating (cooling) the alloy 95% Pb + 5% Sb (Fig. 3, b) at a temperature of 245 °C, there will be a horizontal section on the graph. Further, when heated (cooled) at a temperature of 300 ° C, there will be an inflection in the curve; at this temperature, the alloy will begin to melt (when heated) or crystallize (when cooled). When heating (cooling) the alloy 87% Pb + 13% Sb (Fig. 3, c) at a temperature of 245 °C there will also be a horizontal section. At this temperature the alloy begins to melt and finishes melting at a temperature of 245 °C.

When heating (cooling) the alloy 60% Pb + 40% Sb (Fig. 3, e) to a temperature of 245 °C, no changes occur in the structure of the alloy. At a temperature of 245 °C, lead begins to melt - there will be a horizontal section on the graph. With further heating (cooling) at a temperature of 350 °C, the alloy melts (when heated) or begins to crystallize (when cooled).

When 100% of antimony (Fig. 3, e) is heated (cooled) to a temperature of 631 °C, the alloy will have a solid phase, and at a temperature of 631 °C there will be a horizontal section on the graph, antimony begins to melt. Due to the absorption of energy, the melting of antimony occurs at a temperature slightly below 631 ° C.

To visualize the characteristics of the lead-antimony alloy, we construct the following graph. On the ordinate axis we plot the heating (cooling) temperatures from the normal temperature. On this axis we will plot the critical points for 100% lead. On the abscissa axis we plot the mass fraction of lead and antimony in the alloy. On the right we draw the temperature axis for 100% antimony content. Next, on the ordinate axis we project the critical points obtained as a result of heating the previously considered alloys.

As we can see from the graphs, the first phase change of the alloys occurs at a temperature of 245 °C. We draw a horizontal straight line DE corresponding to this temperature. On the lead temperature axis we project a point corresponding to a temperature of 327 °C - the melting point of pure lead. Let us denote the resulting point by the letter A.

On the antimony temperature axis we project a point corresponding to 631 °C - the melting point of antimony. Let us denote the resulting point by the letter C. On the x-axis, from the point corresponding to 87% Pb and 13% Sb, restore the perpendicular (dotted line) to the horizontal straight line DE (melting temperature of this alloy). Point A (critical temperature 327 °C) on the ordinate axis is connected to the critical point lying on the horizontal line corresponding to the melting point of this alloy (87% Pb + 13% Sb). Let us denote the resulting point by the letter B.

On the abscissa axis, from the point corresponding to 95% Pb and 5% Sb, we restore the perpendicular to the intersection with the segment AB. At this point we have a critical temperature of 300 °C - the melting (solidification) temperature of the alloy 95% Pb + 5% Sb.

On the abscissa axis, from the point corresponding to 60% Pb and 40% Sb, we restore the perpendicular to the intersection with the segment BC, we obtain a point that corresponds to the critical temperature of 350 ° C - melting (solidification) of the alloy 60% Pb + 40% Sb.

Thus, we have obtained a phase diagram of the two-component lead-antimony alloy. All Pb-Sb alloys, regardless of the mass fraction of components, up to a temperature of 245 °C have a solid phase - a mechanical mixture. The alloy along the DBE line begins to slowly melt when heated and solidifies when cooled. This line is called the solidus line (from the Latin solidus - solid).

Along the ABC line, alloys melt when heated, and when cooled they begin to slowly crystallize. This line is called the liquidus line (from the Latin liquidus - liquid). Between the DBE lines and the ABC line, the alloys are in a semi-liquid state. An alloy with 87% Pb and 13% Sb has the lowest melting (solidification) temperature. This alloy, like pure metals, melts at one temperature. Such alloys are called eutectic alloys.

Eutectic is a finely dispersed mechanical mixture of two components formed at a melting temperature (crystallization) significantly lower than the melting temperature of the fused components during the solidification process. Alloys to the left of the eutectic are called hypoeutectic, and those to the right are called hypereutectic.

Let us consider the phase states of the lead-antimony alloy. Above the ABC line the alloy is in a liquid state (liquid phase), between the AB and DB lines it is in a semi-liquid state (Pb + liquid). Below the DB line, the alloy consists of a mechanical mixture of lead and eutectic. Between the lines BC and BE the alloy will have a semi-liquid phase and antimony crystals. Below line BE, the alloy will consist of a mechanical mixture (eutectic and antimony).

The phase diagram of the Pb - Sb alloy refers to the type of diagrams in which the alloyed components dissolve indefinitely in the liquid state and do not dissolve in the solid state, forming mechanical mixtures (eutectic).

By analyzing the state diagram of alloys, you can study the following characteristics: melting (crystallization) temperature, types of alloy structures, ability to form segregation, heat treatment and pressure treatment modes. When studying the phase diagrams of two-component alloys, attention should be paid to the transformation of the alloy components in the crystalline (solid) state.

In this regard, the following features of allotropic changes in alloys are distinguished (typical phase diagrams):

• phase diagrams of the first kind - for alloys, the components of which are completely dissolved in the liquid state, limitedly dissolved in the solid state and form mechanical mixtures (Pb-Sb, Sn-Zn, etc.);
• phase diagrams of the second kind - for alloys, the components of which completely dissolve in the liquid and solid states with the formation of solid solutions (Ag-Au, Cu-Ni; Fe-V, etc.);
• phase diagrams of the third kind - for alloys, the components of which are unlimitedly soluble in the liquid state, practically insoluble in the solid state and form mechanical mixtures (eutectic) with a polymorphic transformation (primary and secondary) of the structural-phase composition;
• phase diagrams of the fourth kind - for alloys, the components of which in the liquid state dissolve in each other, and in the solid state form stable or unstable chemical compounds.

288

Examples of problem solving

Then the mass of alloys will be:

The ratio of the mass of tin in the new alloy to the mass of the new alloy is:

Copper alloys are a compound of a non-ferrous metal with some elements of the periodic table. During their formation, the atoms of the copper crystal lattice are replaced by atoms of another substance. As a result, a new solid compound is formed. Each of them has its own physical and chemical characteristics.

Most often, bronze and brass are made from copper by adding zinc and tin. New connections reduce the price of the base metal, improving some parameters. There is an increase in ductility and corrosion resistance. This makes it possible to use them in some industries.

Metal intensity

Many metals are subject to corrosion, that is, spontaneous destruction as a result of external influences. Enterprises may suffer losses due to corrosion. This is due not only to the high aggressiveness of technological environments and the harsh operating conditions of the equipment, but also to the high metal consumption of the equipment. Metal intensity is the amount of metal that is consumed to create a metal product.

Thus, alloys are used in almost all industries. Homogeneous mixtures of metals have high strength and reliability. They are classified according to various criteria, which makes it possible to increase the efficiency of using alloys. The list of metal alloys is updated every year.

Historical perspective

According to historical data, the first copper alloy appeared by 7 thousand BC. Later, tin was used as an additive. At this time, called the Bronze Age, weapons, mirrors, dishes and jewelry were made from such material.

Read also: Lever mechanical measuring instruments

Production technology has changed. Additives appeared in the form of arsenic, lead, zinc and iron. Everything depended on the requirements for the subject. The material for jewelry required a special approach. The alloy composition consisted of copper, tin and lead.

Since the 8th century. BC e. In Asia Minor, the technology for producing brass was developed. At this time, they had not yet learned how to mine pure zinc. Therefore, its ore was used as a raw material. Over time, the production of copper alloys has constantly expanded and is still at the forefront.

Alloys of the chemical element copper

Copper, when combined with other metals, forms alloys with new properties. The main additives used are tin, nickel or lead. Each type of connection has special characteristics. Copper is rarely used separately because it has low hardness.

A little about bronze

Bronze is the name of an alloy of copper and tin. The compound also contains silicon, lead, aluminum, manganese, and beryllium. The resulting material has higher strength indicators than copper. It has anti-corrosion properties.

In order to improve the characteristics, alloying elements are added to the alloy: titanium, zinc, nickel, iron, phosphorus.

There are several types of bronze:

1. Deformable. The amount of tin does not exceed 6%. Thanks to this, the metal has good ductility and can be processed under pressure.
2. Foundries. High strength allows the material to be used for work in difficult conditions.

Nickel and copper alloy

This connection uses copper and nickel. If other elements are added to this pair, the compounds have the following names:

1. Kuniali. To 6–13% nickel, 1.5–3% aluminum is also added. The rest is copper.
2. Nickel silver. Contains 20% zinc and 15% chromium.
3. Cupronickel. 1% manganese present.
4. Kopelem. Alloy containing 0.5% manganese.

Brass

This is an alloy of copper and zinc. Fluctuations in the quantitative content of zinc entail a change in the characteristics and color of the alloy.

In addition to these 2 main elements, the alloy contains alloying additives. Their figure is a small percentage.

Brass has high strength characteristics, ductility and the ability to resist corrosion. It is also characterized by non-magnetic properties.

Metal classification

In nature, there are several types of metals that differ in their properties, characteristics and appearance. Each variety behaves differently when interacting with other materials or under the influence of environmental factors.

Types of metals

Black

This group includes iron and alloys based on it. Characteristic features of ferrous metals:

• high density;
• the melting point is much higher than that of representatives of other groups;
• color - dark gray.

Representatives of the group of ferrous metals include: tungsten, chromium, cobalt, molybdenum, iron, nickel, titanium, manganese, uranium, neptunium, plutonium and others. They are used in various industries and have different properties. Steel and cast iron are considered popular.

The composition of ferrous metals includes not only iron, but also various impurities, which include sulfur, phosphorus or silicon. They contain different amounts of carbon in their composition.

Colored

Representatives of this group are more in demand. This is due to the fact that non-ferrous metals are used in more industries. They can be used in mechanical engineering, advanced technologies, radio electronics, and metallurgy. Key features of non-ferrous metals:

• low melting point;
• large color spectrum;
• good ductility.

Due to the low strength of representatives of the color group, they are used in conjunction with different types of denser materials. Representatives of this group: magnesium, aluminum, nickel, lead, tin, zinc, silver, platinum, rhodium, gold and others.

Gold bars (Photo: pixabay.com)

Soft

It is possible to distinguish certain types of metals, which will belong to the group of hard and soft. The soft ones are:

1. Aluminum - has corrosion resistance, light weight, good ductility. It is used in the electrical industry, in the construction of aircraft and in the manufacture of dishes.
2. Magnesium is a lightweight material that is susceptible to corrosive processes. To get rid of this drawback, it is used in alloys with other materials.

These are key representatives of the group of soft metals.

Solid

Popular materials in this group are:

1. Tungsten is considered the most refractory metal. In addition to this, it is one of the most durable. Resistant to chemical influences.
2. Titanium - the fewer inclusions of other materials in this metal, the stronger it becomes. It is used in the construction of cars, rockets, airplanes, ships, as well as in the chemical industry. It is well processed under pressure and is not susceptible to corrosive processes.
3. Uranium is another metal considered one of the strongest in the world. It is radioactive and is used in various industries.

Representatives of the “hard group” are less amenable to processing and are used in fewer areas of human activity than soft ones.

Physical and chemical properties of alloys

The chemical composition and mechanical properties of copper alloys provide them not only with strength, but also with good electrical and thermal conductivity. This especially applies to brass.

All copper alloys are characterized by good anti-friction properties. Bronze is especially worth noting.

Due to the good anti-friction properties of bronze, the material is used for the manufacture of bushings as sliding bearings. Such a product does not require lubrication, since all roughness is crushed from the inner diameter along which sliding occurs. This is precisely the source of lubrication. Installation of such bearings is carried out even on high-precision equipment - jig boring and jig grinding machines.

The melting point of copper without additives is 1083 degrees. Depending on the amount of zinc and tin added, this indicator changes. The melting point of brass is 900–1050 degrees, and that of bronze is 930–1140 degrees.

Read also: DIY soldering iron sponge

The corrosion properties of copper alloys are resistant. This is due to the fact that copper is not an active element. Polished surfaces are especially non-corrosive.

The corrosion resistance of copper compounds occurs in fresh water and is impaired in the presence of acid, which prevents the formation of a protective coating.

What metal alloys are produced?

Alloys are substances that are structurally homogeneous and contain two or more chemical elements, mainly metals. The base for the manufacture of most alloys is made up of several metallic materials with the addition of modifying and alloying impurities. In addition, the alloy may contain remaining inclusions of natural, accidental and technological origin.

Depending on the production technology, there are two categories of alloys:

1. Cast . For their production, a fairly popular method is used - crystallization of a homogeneous consistency based on hot particles.

2. Powder alloys . They are formed as a result of the action of a press on a mixture of various powders, which are sent to a special oven and undergo a high-temperature treatment cycle. For the feedstock, metal powder and several chemical compounds are used. For example, the production of hard alloys involves the use of tungsten or titanium carbides.

Taking into account the method of obtaining the finished material, 2 types of alloys are distinguished:

1. Foundries (these include cast iron and silumin).

2. Deformable (powder alloys and steel).

In different industrial sectors, many subtypes of alloys are used - tool, special, structural. Depending on the scope of application, they are divided into several types. Structural alloys include cast iron, steel, duralumin and compounds with special properties, for example, anti-friction characteristics and resistance to sparking.

This category also includes the following materials:

1. Brass.

2. Bronze.

3. Alloys for the manufacture of bearings.

4. Babbitt.

5. Alloys for electric heating and measuring equipment.

6. Nichrome.

7. Manganin.

8. Blanks for the production of cutting tools.

9. Will win.

Corrosion-resistant, heat-resistant, low-melting, temperature-electric, magnetic and amorphous alloys are also suitable for industrial purposes. The number of varieties that are currently used is quite large and is constantly increasing. Alloys are classified according to two criteria:

1. Iron-based materials.

2. Non-ferrous metal alloys.

Below are the most popular and important alloys for industrial production with the main areas of their use.

Steel.

By steel we mean a compound of iron and carbon (the concentration of the latter is 2%). Due to the inclusion of various alloying impurities such as vanadium, chromium or nickel, steel acquires alloyed properties.

Of all existing varieties of alloys, steel occupies leading positions in terms of supply and production volumes. The areas of their operation are very wide, so it is quite difficult to indicate all areas.

Low-carbon steels, which contain up to 0.25% carbon, are used for structural purposes, and those with a much higher percentage (from 0.55) are used in the production of low-speed cutting devices, drills and razor blades. Alloyed subtypes are in demand in the mechanical engineering industry and in the manufacture of high-speed equipment.

Cast iron.

An alloy of iron with 2-4% carbon is called cast iron. Another essential element of this material is silicon. Cast iron alloys are used in the manufacture of various products with utilitarian functions, for example, manhole covers, pipeline fittings, engine cylinder blocks. A properly cast product has improved mechanical characteristics.

Copper alloys.

This category of alloys is represented by various subtypes of brass, i.e. copper-based materials containing from 5 to 45% zinc. If 5 to 20% zinc is added to brass, it is called red (tompak), and when the zinc concentration is in the range of 20-36%, the alloy is called yellow brass (alpha brass).

This variety is widely in demand in the manufacture of small parts that require special machinability and accuracy.

In addition, copper alloys with the addition of aluminum, silicon and tin or beryllium are used for industrial purposes.

For example, phosphorus and silicon bronze (a copper alloy with the addition of silicon) have excellent strength characteristics and are used in the production of membranes and springs.

Lead alloys.

Essential materials for the soldering process. Regular solder contains 1 part lead and 2 parts tin. The metal alloy is in demand for soldering electrical wires and pipeline components.

Antimony-lead alloys are used to make shells for telephone cables and battery plates. Alloys using cadmium, tin and bismuth have a melting point that is much lower than the boiling point of the liquid (70°C). Because of this feature, they are used in the production of valves for fire-fighting equipment of sprinkler systems.

Pewter alloy, indispensable for the manufacture of decorative kitchen utensils and jewelry, consists of 85-90% tin. The remainder of the composition is lead. Lead is also added when developing so-called babbitts, which are bearing alloys. Lead alloys also contain arsenic, tin and antimony.

Light alloys.

In mechanical engineering, light alloys with improved strength properties, resistance to high temperatures and mechanical stress are in demand. Beryllium, magnesium, titanium and aluminum are used as raw materials for the manufacture of the material. Not all magnesium and aluminum alloys are suitable for use in high-temperature and aggressive environments.

Aluminum alloys.

This category includes casting alloys (aluminum and silicon), high-pressure casting alloys (magnesium and aluminum), and high-strength hardening alloys based on aluminum and copper.

The main advantage of aluminum alloys is their low cost and strength at low temperatures, as well as ease of processing. The workpiece can be simply forged, stamped or used for drawing, extruding and deep drawing.

The material can be easily welded and processed using metal-cutting equipment. The performance characteristics of aluminum alloys are lost when the temperature rises to 175°C. But due to the formation of an oxide film on the surface, they are not afraid of corrosion processes when exposed to various aggressive conditions.

The alloy is a good conductor of electrical energy and heat, is characterized by enhanced reflective properties, non-magneticity and harmlessness to human health when interacting with food (aluminum products do not rust, do not have any color or taste). In addition, aluminum alloys are protected from explosion, because they do not produce sparks and can suppress impact energy.

Due to the listed features, aluminum alloys are widely used in the automotive industry, car and aircraft construction, construction, for the installation of high-voltage power lines and in the food industry. The presence of a small amount of iron in the alloys increases the safety margin at high temperatures, but negatively affects corrosion resistance and ductility at room temperature.

Magnesium alloys.

This type of alloy is characterized by its low weight and strength, as well as improved casting properties. It is quite easy to process the material by cutting. In this regard, magnesium alloys have found application in the rocket and aircraft industries, where they are used for the production of engines, wheels, housings, fuel tanks and other components.

Certain types of alloys are characterized by an increased viscous damping coefficient; because of these properties, they are used in the production of moving elements of vehicles and structural components that are used in conditions of high vibrations.

The disadvantages of magnesium alloys include softness, instability to wear and insufficient ductility. However, the workpiece is easy to form by heat treatment. In addition, magnesium alloys are suitable for gas, electric arc and resistance welding processing. To ensure high-quality protection of alloys from corrosion, they are coated with a special shell.

Titanium alloys.

In terms of performance characteristics, titanium alloys are many times better than magnesium and aluminum alloys in terms of strength and degree of elasticity. With increased density, they are characterized by special resistance to mechanical stress, second only to beryllium alloys.

Titanium alloys contain a minimum concentration of nitrogen, carbon and oxygen, which makes them quite plastic. Due to their low electrical conductivity and low thermal conductivity coefficient, titanium alloys are resistant to wear and abrasion, and their strength is much higher than that of other magnesium alloys.

The creep of individual grades at average stress reaches 90 MPa, remaining at this level when heated to 600°C, which is much higher than the limit for magnesium and aluminum alloys. Alloys with titanium retain their malleability up to a temperature of 1150°C, so for their processing it is allowed to use electric arc welding with inert gas or spot and seam welding.

It is unjustified to process the material using cutting technology, which is explained by the rapid setting of the cutting device. Melting of titanium alloys is carried out under vacuum conditions or a controlled atmosphere to eliminate the problem of the release of embedded impurities of oxygen and nitrogen into the environment.

Titanium alloys are known to be widely used in the space and aviation industries. On their basis, various mechanisms and parts are produced, which are operated within the temperature range from 150 to 430°C. Components of specialized chemical equipment are also made from titanium.

Unique light armor has been developed from titanium-vanadium alloys for equipment and cockpits of combat aircraft. And for the manufacture of jet engines and aircraft bodies, the main material is an alloy of aluminum, titanium and vanadium.

Beryllium alloys.

Having excellent ductility, beryllium alloy is superior to other metal alloys in terms of specific strength. For its production, the principle of adding brittle grains of beryllium to a soft plastic base, for example, to heated silver, is used.

Being a low-density material, beryllium alloy is actively used in the development of missile guidance systems. Its modulus of elasticity is higher than that of steel or beryllium bronze, which allows the material to be used for the production of springs and contacts in electrical circuits.

In its pure form, the alloy is used as a moderator and neutron reflector in nuclear reactors. Due to the possibility of forming a protective oxide film, it retains its performance characteristics when exposed to high temperatures.

The main difficulty in processing the alloy is related to its toxicity. Fumes from heated beryllium contribute to the development of dangerous health problems, including respiratory diseases and dermatitis.

You can buy metal products based on various alloys through our website. Industrial includes a large number of Russian suppliers of metal products from different regions. The warehouses of our enterprise in the Moscow region store non-ferrous and stainless steel products, products made from specialized alloys and steels, as well as unique raw materials of the metallurgical industry.

In addition, we engage in cutting and casting of metal based on the drawings and documentation provided by the customer. The production process involves strict control using ultrasonic and chemical equipment.

Application of alloys

Due to their properties, copper and its alloys have found application not only in industry, but also in jewelry.

Copper compounds are also used to make the following products:

• wire, due to its good electrical conductivity,
• pipes whose material does not react with water,
• dishes in which bacteria do not grow,
• roofing for a roof that lasts a long time,
• as accessories for furniture.

Methods for obtaining metal

The main copper-based alloys are brass and bronze. Their production process is as follows:

1. Brass. Copper is first smelted. Then the zinc is heated to 100 degrees and it is added at the final stage of brass production. Charcoal is used as a heat source.
2. Bronze. Induction installations are used for its production. First the copper is melted and then the tin is added.

In both cases, ingots are formed and sent to the rolling shop, where they are processed by hot and cold pressure.

Melting copper at home

To obtain a copper alloy at home, you need to make homemade melting equipment. The process is carried out as follows:

1. The support is made of sand-lime brick.
2. A metal mesh with small cells is laid on top.
3. Coal is poured in and heated with a gas burner. To make the fire burn better, a stream of air is directed from the vacuum cleaner.
4. A crucible with small pieces of metal is placed on the fire.
5. At the end of the process, the liquid metal is poured into the mold.

The physical properties of copper alloys have made them indispensable in many areas of economic activity. Aircraft and shipbuilding cannot do without them. It is impossible to imagine watch mechanisms without such metal. Any design that has parts working in pairs needs anti-friction material.

Add your works

Help students just like you! Upload your work to the system so that it becomes available to everyone! We accept coursework, diplomas, essays and much more ;-)

Last update -

Every day more and more new works are added to our database. Visit us often - stay tuned for new products!

mobile version

You can use our scientific search via your mobile phone or tablet directly during lectures and classes!

What are the types and types of metals and their alloys?

In construction, industry and other areas of human life, various types of metals are often used. They differ from each other in the properties by which they are selected and used in a particular area. Materials are obtained in a variety of ways. Certain types of metals are combined together to create alloys that have unique physical and chemical properties.

Characteristics and Signs

Metals are a group of elements in the form of simple substances that have characteristic metallic properties. In nature they are present in the form of ores or compounds. Sciences such as chemistry, physics and metallurgy study the characteristics of these materials.

Metals have a combination of different properties. Mechanical factors determine their ability to resist deformation and destruction. Technological methods help determine the ductility of materials to various types of processing. Chemical properties show their interaction with different substances, and physical properties indicate their behavior in thermal, gravitational or electromagnetic fields.

Metals are classified according to the following properties:

• Hardness is the resistance of a material to penetration by another.
• Strength - preservation of shape, structure and size after exposure to dynamic, static and alternating loads.
• Elasticity is a change in shape without violating integrity during deformation and the possibility of returning to its original form.
• Plasticity is the retention of the resulting shape and integrity under the influence of forces.
• Wear resistance - maintaining external and internal integrity under the influence of prolonged friction.
• Viscosity - maintaining integrity under increasing physical stress.
• Fatigue is the number and period of cyclic impacts that a metal can withstand without changing its integrity.
• Heat resistance - resistance to high temperatures.

The primary characteristic of metals is the negative conductivity coefficient of electricity, which increases when the temperature drops, and is partially or completely lost when the temperature rises.

Secondary characteristics of materials are metallic luster and high melting point.

In addition, some types of metal compounds can be reducing agents in redox reactions.

Metallic properties are interrelated, since the components of the material affect all other parameters. Metals are divided into ferrous and non-ferrous, but they are classified according to many criteria.

Group with iron and its alloys

Ferrous metals are characterized by impressive density, high melting point and dark gray color. This group mainly includes iron and its alloys. To impart specific properties to the latter, alloying components are used.

We recommend: Types of industrial waste and waste in production

Subgroups of ferrous metals:

• Iron - iron, cobalt, manganese, nickel. They are usually taken as a base or as an additive to alloys.
• Refractory - tungsten, molybdenum, titanium, chromium. They melt at a temperature higher than the melting level of iron. Alloy steels are obtained from refractory varieties.
• Rare earths - lanthanum, neodymium, cerium. They have related chemical properties, but differ in physical parameters. Used as an additive to alloys.
• Uranium (actinides) - actinium, neptunium, plutonium, thorium, uranium. Widely used in nuclear energy.
• Alkaline earths - calcium, lithium, sodium. They are not used in free form.

Metals of the ferrous group are represented by iron alloys with different carbon content and the content of additional chemical elements: silicon, sulfur or phosphorus. Popular materials are steel and cast iron. Steel contains up to 2% carbon.

It is characterized by good ductility and high technological performance. In cast iron, the carbon content can reach 5%.

The properties of the alloy may differ with different chemical elements: with the content of sulfur and phosphorus, brittleness increases, and with chromium and nickel, cast iron becomes resistant to high temperatures and corrosion.

Colored varieties

Non-ferrous metals are more in demand than ferrous metals, since most of them are raw materials for the production of rolled metal. This group of materials has a wide range of applications: they are used in metallurgy, mechanical engineering, radio electronics, high technology and other fields.

Classification by physical parameters:

• Heavy - cadmium, nickel, tin, mercury, lead, zinc. Under natural conditions, they are formed in strong compounds.
• Lightweight - aluminum, magnesium, strontium, titanium and others. Characterized by a low melting point.
• Noble ones - gold, platinum, rhodium, silver. They are characterized by increased resistance to corrosion.

Non-ferrous metals are characterized by low density, good ductility, low melting point and predominant colors (white, yellow, red). Various equipment is made from them. Since the strength of the materials is quite low, they are not used in their pure form. Light alloys for various purposes are produced from them.

Materials of this group are characterized by impressive atomic weight and density, exceeding that of iron.

We recommend: Waste paper grades: MS 1A, 5B and 13B: collection and use

Copper, which acts as a conductor of electric current, is in great demand.

It is characterized by a pinkish-red hue, low resistivity, good thermal conductivity, low density, excellent ductility and corrosion resistance. In the technical field, copper alloys are used: bronze (with the addition of aluminum, nickel or tin) and brass (with zinc).

Bronze is used in the production of membranes, round and flat springs, worm gears and various fittings. Tapes, sheets, wire, pipes, bushings, and bearings are made from brass.

The group of heavy metals is one of the main causes of environmental pollution. Toxic substances enter the oceans through wastewater from industrial plants. Some varieties of the heavy group can accumulate in living organisms.

Mercury is a highly toxic metal for humans. When coal is burned at power plants, its compounds pass into the atmosphere, and then are converted into sediment and end up in water bodies. Inhabitants of freshwater and marine systems accumulate large amounts of a dangerous substance, which leads to poisoning or death of people.

Cadmium is considered a trace element and a fairly rare element that can enter the ocean through wastewater from metallurgical plants. This substance is present in small quantities in the human body, but at high levels it destroys bone tissue and leads to anemia.

Lead is present in a dispersed state almost everywhere. When there is an excess of metal in the human body, health problems are observed.

Soft types

Silver-white aluminum is characterized by lightness, high corrosion resistance, good electrical conductivity and ductility. The characteristics of the material have made it useful in aircraft construction, the electrical industry and food production. Aluminum alloys are used in mechanical engineering.

Magnesium has low corrosion resistance, but the lightweight material is indispensable in the technical field. Alloys with this metal use aluminum, manganese and zinc, which are easy to cut and have high strength. Magnesium alloys are used in the production of cases for cameras, engines and other devices.

Titanium is used in mechanical engineering, the rocket industry and the chemical industry. Alloys containing this substance are characterized by low density, excellent mechanical properties, corrosion resistance and flexibility in pressure treatment.

Noble materials

Some types of metals are rarely found in nature and require labor-intensive extraction methods. The noble group metals are:

• Gold.
• Silver.
• Platinum.
• Rhodium.

We recommend: Features of types of plastics, table and types of plastic

People learned about gold back in the Stone Age. The most expensive metal in the world can be found in nature in the form of nuggets, which contain a small amount of impurities. It is also found in alloys with silver.

Gold has thermal conductivity and very low resistance. Due to its good malleability, the material is used in the manufacture of jewelry.

Silver comes second in value after gold. In nature, it is usually found as silver ore. Silver is characterized by softness, ductility, thermal and electrical conductivity.

Platinum, discovered in the mid-20th century, is a rare material that can only be found in deposits of various alloys. It is quite difficult to obtain. The value of the metal lies in the fact that it is not affected by acids. When heated, platinum does not change color and does not oxidize.

Rhodium is also a noble metal. It has a silver color with a blue tint. Rhodium is resistant to chemical influences and temperature changes, but the fragile metal deteriorates under mechanical stress.

Hardness classification

Metals are also divided into hard and soft.

The hardest pure material in the world is chromium . It belongs to the refractory varieties and lends itself well to mechanical processing. Another solid element is tungsten.

It is characterized by high melting point, heat resistance and flexibility. Various parts are forged from it and small elements necessary for lighting fixtures are made. Tungsten is often present in heavy alloys.

Hard metals are not only difficult to mine, but also difficult to find on the planet. They are mainly found in meteorites that fell to Earth.

The softest metals include potassium, sodium, rubidium and cesium. Also in this group are gold, silver, copper and aluminum. Gold is present in marine complexes, granite fragments and the human body. External factors can destroy valuable metal.

Soft silver is used in the manufacture of dishes and jewelry. Sodium is widely used in almost every industrial sector.

Mercury, the softest metal in the world, is used in the agricultural and chemical industries, as well as electrical engineering.