The behavior of the elements in an alloy and their influence on their properties generally depend on three factors: the type and number of alloy partners, their mass fraction in the alloy and the temperature.

In metallurgy, an alloy (from Latin ligare 'bind, unite') is a macroscopically homogeneous metallic material made up of at least two elements (components), at least one of which is a metal and which together have the metal-typical characteristic of the metal bond. [1] From a chemical point of view, there are alloys that represent mixtures and intermetallic compounds with a defined stoichiometric ratio of the metals involved. In general, alloys also have a crystalline structure. However, there are also amorphous metallic glasses.

Depending on the type of alloy formation, an alloy can be more homogeneous or heterogeneous at the microscopic level. Alloys that form exclusively mixed crystals or exclusively intermetallic compounds are homogeneous. All others, which consist of several phases, are heterogeneous. [2]

The behavior of the elements in an alloy and their influence on their properties generally depend on three factors: the type and number of alloy partners, their mass fraction in the alloy and the temperature. These factors determine the respective absorption capacity, i.e. the solubility of one element in the other and whether the alloy partners form mixed crystals or mixtures of pure crystals (also crystal mixtures) of the respective alloy components.

The verb verb is originally from the Latin ligare and means to bind together, to connect or to unite. In the 17th century, the now slightly modified legare (with the same meaning) was adopted into German.

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Alloy 625 / Inconel 625 / N06625 / 2.4856

Alloy 601 / Inconel 601 / N06601 / 2.4851

Alloy 718 / Inconel 718 / N07718 / 2.4668

Alloy 690 / Inconel 690 / N06690 / 2.4642

Alloy 617 / Inconel 617 / N06617 / 2.4663

Alloy X-750 / Inconel X-750 / N07750 / 2.4669

Alloy 600 / Inconel 600 / N06600 / 2.4816

1.4876 / 1.4958: Corrosion-resistant and heat-resistant nickel-iron-chrome alloy

Alloy 800HT / Incoloy 800HT / N08811 / 1.4959

Alloy 825 / Incoloy 825 / N08825 / 2.4858

Alloy 800H / Incoloy 800H / N08810 / 1.4958

Alloy 20 / Incoloy 20 / N08020 / 2.4660

Alloy 925 / Incoloy 925 / UNS N09925

Alloy B-2 / Hastelloy B-2 / N10665 / 2.4617

Alloy C-276 / Hastelloy C-276 / N10276 / 2.4819

Alloy C-22 / Hastelloy C-22 / N06022 / 2.4602

Alloy B-3 / Hastelloy B-3 / UNS 10675 / 2.4600

Alloy C-4 / Hastelloy C-4 / N06455 / 2.4610

Alloy X / Hastelloy X / N06002 / 2.4665

Alloy 400 / Monel 400 / UNS N04400 / 2.4360

Alloy K-500 / Monel K-500 / N05500 / 2.4375

Alloy R-405 / Monel R-405 / N04405

properties
The alloy element can form a solid solution with the basic element (single-phase alloy) or several phases can be formed. While the properties of single-phase alloys are essentially determined by their chemical composition, those of multi-phase alloys are also significantly influenced by the distribution of the phases (structure). Base metal and alloy elements are also called components of an alloy. They are listed in the list of alloying elements and their effects on the respective base metals. Mixed crystals have a higher hardness and tensile strength, but a lower melting temperature than the base metal. In the case of metals, the electrical conductivity also drops. For the relatively soft, pure metals, solid solution strengthening is one of four possible strength-increasing processes to produce a hard material.

With the solidification of a cast alloy, the crystallization is not always complete. Certain alloys can also improve their mechanical properties (fracture resistance, hardness, elongation) as a casting - stored cold or warmed - ("tempered"). In the case of wrought alloys, the recrystallization that solidifies the structure by cold aging or heat treatment is even a prerequisite for the production of semi-finished products.

Examples of "natural alloys" are Elektrum, a gold-silver alloy, and Stibarsen, an antimony-arsenic alloy.

In the case of ��artificially produced alloys��, a distinction is made between those that were deliberately manufactured in order to change the material properties (examples of hardness, corrosion resistance) of the ��base metals�� in the desired way, and those that are created unintentionally because foreign substances (metallurgy) are already produced get into the alloy and can have negative effects on the material properties. Examples of the latter include bismuth and / or arsenic in Messingen, as well as bismuth in AlSi alloys, where it greatly affects the microstructure.

history
Copper, tin and bronze
Bronze ax
Bronze ax
Copper is one of the first metals used by humans; it was probably discovered by chance about 6000 to 10000 years ago in charcoal fires, which burned particularly hot with air. It gave the Copper Stone Age its name. At a melting point of 1083 �� C, it can escape from copper veins in the rock in liquid form. By heating copper-containing, oxidic ores, on the other hand, copper can only be obtained with a reducing furnace, i.e. in the presence of charcoal. Tin was also discovered early, about 5000 years ago. [4]

Bronze as an alloy of copper and tin (CuSn) has been around since about 3300 BC. BC in Palestine. Bronze is harder and more cut than copper and gave an entire cultural epoch its name, the Bronze Age. Commodities, tools, weapons and jewelry were made of bronze. Many sculptures are still cast from bronze.

Brass
Brass figure
Brass figure
Brass is an alloy of copper and zinc (CuZn). Zinc, mostly in the form of zinc carbonate "calamine" (smithsonite), has been around 3000 BC since the Bronze Age. Used in Babylon and Assyria, in Palestine around 1400 to 1000 BC Chr. [6] Brass quickly became an important coin metal in coinage, but because of its beautiful, golden sheen, it was also often used to make jewelry and plastics.

Iron alloys
Iron sickle
Iron sickle
Iron alloys have been used in prehistoric times, but only from meteorites, which often contain the iron-nickel (FeNi) alloy. Since meteorites were rarely found, iron objects were valuable. The Sumerians called it "heavenly metal", the ancient Egyptians "black copper from the sky". [7] Smelted iron (detected by the absence of nickel) was found in Mesopotamia, Anatolia and Egypt and is about 3000 to 2000 BC. Chr. It was more valuable than gold and was used primarily for ceremonial purposes. However, iron offered and offers many advantages, the most important being the greater hardness compared to bronze and copper. Improvements in extraction and processing caused people to start making weapons and then tools such as plows from iron. The Bronze Age was thus replaced by the Iron Age.

Classification
Depending on the number of components in the alloy, one speaks of a two-, three-, four- or multi-component alloy (binary, ternary, quaternary or polynary alloy), whereby only those components are counted that determine the characteristic properties. Since iron and steel are of particular importance in technology, alloys are divided into iron and non-iron alloys. Further classifications result from the type of alloy formation, since these do not only result from the melting together of the components or also from the special capabilities of alloys.

Natural alloys are created by exposure to heat and melting elements, for example inside celestial bodies. Since these alloys were not controlled by humans, they are not subject to their defined compositions and properties.
Iron alloys are divided into cast iron and steel. The distinction is based on the carbon content. See main article iron-carbon diagram. Stainless steels are particularly important: alloyed or unalloyed steels with a particular degree of purity.
Non-ferrous alloys (non-ferrous alloys, e.g. bronze, brass, amalgams, white gold, rose gold) are alloys based on non-ferrous metals.
Diffusion alloys are created by the diffusion of atoms into the crystal lattice of the base metals. Because of the smallness of their atoms compared to the base metal, the first elements in the periodic table in particular are able to migrate into its crystal lattice. The best example of a diffusion alloy is the carburizing of workpieces in order to be able to harden them (see tempering).
Heusler's alloys are very special ferromagnetic alloys that do not contain iron, cobalt or nickel (example Cu2AlMn).
Shape memory alloys are metals that return to their original shape after being deformed by exposure to heat.
Cast alloys are used for direct shaping.
Wrought alloys as a ��semi-finished product�� are an intermediate product that is intended for further rolling, pressing or drawing forming.
Pseudo-alloys are the workpieces created by sintering (pressing together various, intimately mixed metal powders at high temperature). This process can also be used to mix elements that would not dissolve in the molten state. Many tungsten alloys are used e.g. B. manufactured in this way.
Alloy formula
In order to identify an alloy, the base metal is usually mentioned first, followed by the key component (s) as an abbreviation for the metal with an attached number, which represents the respective percentage (mass percentage). An alloy CuZn37 (formerly called brass 63) consists of the copper base, to which 37% zinc has been added. With the iron-carbon alloy steel, there are deviations from this system depending on the amount of the alloying elements. In any case, the iron is never explicitly mentioned. Steel C37, for example, contains 0.37% carbon and otherwise iron.

The specification of alloy proportions is partly due to the DIN 1310 composition of mixed phases (gas mixture, solutions, mixed crystal); Basic terms regulated.

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