An alloy is a partial or complete solid solution A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase.This often happens when the two elements involved are close of one or more elements A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, in a metallic A metal is a chemical element that is a good conductor of both electricity and heat and forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are surrounded by matrix The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous A substance that is uniform in composition is a definition of homogeneous in Chemistry. This is in contrast to a substance that is heterogeneous in distribution depending on thermal (heat treatment) history. Alloys usually have different properties from those of the component elements.

Alloys' constituents are usually measured by mass.

Theory

Alloying one metal with other metal(s) or non metal(s) often enhances its properties. For example, steel Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing is stronger than iron Iron is the most common element in the earth as a whole, and the fourth most common in the Earth's crust. It is produced as a result of stellar fusion in high-mass stars, and it is the heaviest stable element produced by stellar fusion because the fusion of iron is the last nuclear fusion reaction that is exothermic. Iron is the most widely used, its primary element. The physical properties, such as density The density of a material is defined as its mass per unit volume. The symbol of density is ρ . In some countries (for instance, in the United States), density is also defined as its weight per unit volume . The density of a substance is the reciprocal of its specific volume, a representation commonly used in thermodynamics, reactivity Reactivity is a somewhat vague concept used in chemistry which appears to embody both kinetic and thermodynamic factors. For example, it is commonly asserted that 'the reactivity of group one metals increases down the group in the periodic table, or that hydrogen's reactivity is evidenced by its reaction with oxygen. In fact, the rate of reaction, Young's modulus In solid mechanics, Young's modulus, also known as the tensile modulus, is a measure of the stiffness of an isotropic elastic material. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. This can be experimentally determined from the slope of a stress-strain curve created, and electrical Electrical conductivity or specific conductance is a measure of a material's ability to conduct an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current. The conductivity σ is defined as the ratio of the current density J to the electric field strength and thermal conductivity In physics, thermal conductivity, k, is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction. Thermal conductivity is measured in watts per kelvin per metre . Multiplied by a temperature difference (in kelvins, K) and an area (in square metres, m2), and divided by a, of an alloy may not differ greatly from those of its elements, but engineering properties, such as tensile strength Tensile strength is indicated by the maxima of a stress-strain curve and, in general, indicates when necking will occur. As it is an intensive property, its value does not depend on the size of the test specimen. It is, however, dependent on the preparation of the specimen and the temperature of the test environment and material^[1] and shear strength Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear may be substantially different from those of the constituent materials. This is sometimes due to the sizes of the atoms The atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons . The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain in the alloy, since larger atoms exert a compressive force on neighboring atoms, and smaller atoms exert a tensile force on their neighbors, helping the alloy resist deformation. Sometimes alloys may exhibit marked differences in behavior even when small amounts of one element occur. For example, impurities in semi-conducting ferromagnetic Ferromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished. Ferromagnetism is the strongest type; it is the only type that can produce forces strong enough to be felt, and is responsible for the common phenomena of alloys lead to different properties, as first predicted by White, Hogan, Suhl, Tian Abrie and Nakamura.^[2][3] Some alloys are made by melting and mixing two or more metals. Bronze Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, or silicon. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal, an alloy of copper and tin Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest, was the first alloy discovered, during the prehistoric Prehistory is a term used to describe the period before recorded history. Paul Tournal originally coined the term Pré-historique in describing the finds he had made in the caves of southern France.[citation needed] It came into use in France in the 1830s to describe the time before writing, and the word "prehistoric" was introduced into period now known as the bronze age The Bronze Age of a culture is the period when the most advanced metalworking in that culture used bronze. This could either have been based on the local smelting of copper and tin from ores, or trading for bronze from production areas elsewhere. Many, though not all, Bronze Age cultures flourished in prehistory; it was harder than pure copper and originally used to make tools and weapons, but was later superseded by metals and alloys with better properties. In later times bronze has been used for ornaments In architecture and decorative art, ornament is a decoration used to embellish parts of a building or object. Architectural ornament can be carved from stone, wood or precious metals, formed with plaster or clay, or impressed onto a surface as applied ornament; in other applied arts the main material of the object, or a different one may be used, bells A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, which resonates upon being struck. The striking implement can be a tongue suspended within the bell, known as a clapper, a small, free sphere enclosed within the body of the bell or a separate mallet or, statues A statue is a sculpture in the round representing a person or persons, an animal, or an event, normally full-length, as opposed to a bust, and at least close to life-size, or larger. Its primary concern is representational, and bearings A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle. Brass Brass is any alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. In comparison, bronze is principally an alloy of copper and tin. Despite this distinction some types of brasses are called bronzes and vice-versa. Brass is a substitutional alloy. It is used for decoration is an alloy made from copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a and zinc.

Unlike pure metals, most alloys do not have a single melting point The melting point of a solid is the temperature at which the vapor pressure of the solid and the liquid are equal. At the melting point the solid and liquid phase exist in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point. Because of the ability of some substances to, but a melting range in which the material is a mixture of solid Solid is one of the major states of matter. It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, and liquid Liquid is one of the three classical states of matter. Like a gas, a liquid is able to flow and take the shape of a container, but, like a solid, it resists compression. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, phases. The temperature at which melting begins is called the solidus In chemistry, materials science, and physics, the solidus is the locus of temperatures below which a given substance is completely solid (crystallized). The solidus is applied, among else, to metal alloys, ceramics, and natural rocks and minerals, and the temperature when melting is just complete is called the liquidus The liquidus temperature, TL or Tliq, is mostly used for glasses, alloys and rocks. It specifies the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium. Above the liquidus temperature the material is homogeneous. Below the liquidus temperature more and more crystals begin to form in the melt if one waits. However, for most alloys there is a particular proportion of constituents (in rare cases two)—the eutectic A eutectic system is a mixture of chemical compounds or elements that has a single chemical composition that solidifies at a lower temperature than any other composition. This composition is known as the eutectic composition and the temperature is known as the eutectic temperature. On a phase diagram the intersection of the eutectic temperature mixture—which gives the alloy a unique melting point.

Terminology

In practice, some alloys are used so predominantly with respect to their base metals that the name of the primary constituent is also used as the name of the alloy. For example, 14 karat The carat is a measure of the purity of gold alloys. In the United States and Canada, the spelling karat is used, while the spelling carat is used to refer to the measure of mass for gemstones (see Carat (mass)) gold Gold is a chemical element with the symbol Au (from Latin: aurum, "shining dawn", hence adjective, aureate) and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial is an alloy of gold with other elements. Similarly, the silver Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals, and used in jewelry and the aluminium Aluminium (UK: /ˌæljʉˈmɪniəm/ AL-yew-MIN-ee-əm) or aluminum (US: /əˈluːmɨnəm/ ( listen) ə-LOO-mi-nəm) is a silvery white member of the boron group of chemical elements. It has the symbol Al and its atomic number is 13. It is not soluble in water under normal circumstances. Aluminium is the most abundant metal in the Earth's crust, used as a structural building material are also alloys.

The term "alloy" is sometimes used in everyday speech as a synonym for a particular alloy. For example, automobile wheels made of an aluminium alloy Aluminium alloys are alloys in which aluminium is the predominant metal. Typical alloying elements are copper, zinc, manganese, silicon, and magnesium. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of are commonly referred to as simply "alloy wheels", although in point of fact steels and most other metals in practical use are also alloys.

History

The use of alloys by humans started with the use of meteoric iron Iron meteorites consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to man, a naturally occurring alloy of nickel Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements that exist around room temperature, the other three being iron, cobalt and gadolinium and iron Iron is the most common element in the earth as a whole, and the fourth most common in the Earth's crust. It is produced as a result of stellar fusion in high-mass stars, and it is the heaviest stable element produced by stellar fusion because the fusion of iron is the last nuclear fusion reaction that is exothermic. Iron is the most widely used. As no metallurgic processes were used to separate iron from nickel, the alloy was used as it was.^[4] Meteoric iron could be forged from a red heat to make objects such as tools, weapons, and nails. In many cultures it was shaped by cold hammering into knives and arrowheads. They were often used as anvils. Meteoric iron was very rare and valuable, and difficult for ancient people to work.^[5]

Iron is usually found as iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite , hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3) on Earth, except for one deposit of native iron in Greenland b. ^ Greenland, the Faeroes and Iceland were formally Norwegian possessions until 1814 despite 400 years of Danish monarchy beforehand, which was used by the Inuit The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark (Greenland), Russia (Siberia) and the United States (Alaska). The Inuit language is grouped under Eskimo-Aleut languages. An Inuk is an Inuit person people. Native copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a, however, was found worldwide, along with silver Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals, and, gold Gold is a chemical element with the symbol Au (from Latin: aurum, "shining dawn", hence adjective, aureate) and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial and platinum Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements. A dense, malleable, ductile, precious, gray-white transition metal,, which were also used to make tools, jewelry, and other objects since Neolithic times. Copper was the hardest of these metals, and the most widely distributed. It became one of the most important metals to the ancients. Eventually, humans learned to smelt metals such as copper and tin Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest from ore An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element, and, around 2500 B.C, began alloying the two metals to form bronze Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, or silicon. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal, which is much harder than its ingredients. Tin was rare, however, being found mostly in Great Britain. In the Middle East, people began alloying copper with zinc to form brass.^[6] Ancient civilizations made use of the information contained in modern alloy constitution diagrams, taking into account the mixture and the various properties it produced, such as hardness, toughness and melting point, under various conditions of temperature and work hardening.^[7]

The first known smelting of iron began in Anatolia, around 1800 B.C. Called the bloomery process, it produced very soft but ductile wrought iron and, by 800 B.C., the technology had spread to Europe. Pig iron, a very hard but brittle alloy of iron and carbon, was being produced in China as early as 1200 B.C., but did not arrive in Europe until the Middle Ages. These metals found little practical use until the introduction of crucible steel around 300 B.C. These steels were of poor quality, and the introduction of pattern welding, around the first century A.D., sought to balance the extreme properties of the alloys by laminating them, to create a tougher metal.^[8]

Mercury had been smelted from cinnabar for thousands of years. Mercury dissolves many metals, such as gold, silver, and tin, to form amalgams, (an alloy in a soft, paste, or liquid form at ambient temperature). Amalgams have been used since 200 B.C. in China for plating objects with precious metals, called gilding, such as armor and mirrors. The ancient Romans often used mercury-tin amalgams for gilding their armor. The amalgam was applied as a paste and then heated until the mercury vaporized, leaving the gold, silver, or tin behind.^[9] Mercury was often used in mining, to extract precious metals like gold and silver from their ores.^[10]

Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae, gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Silver was often found alloyed with gold. These metals were also used to strengthen each other, for more practical purposes. Quite often, precious metals were alloyed with less valuable substances as a means to deceive buyers.^[11] Around 250 B.C., Archimedes was commissioned by the king to find a way to check the purity of the gold in a crown, leading to the famous bath-house shouting of "Eureka!" upon the discovery of Archimedes principle.^[12]

See also

• List of alloys
• Intermetallics
• Heat treatment
• CALPHAD (method)

References

1. ^ Adelbert Phillo Mills, (1922) Materials of Construction: Their Manufacture and Properties, John Wiley & sons, inc, 489 pages, originally published by the University of Wisconsin, Madison
2. ^ C. Michael Hogan, (1969) Density of States of an Insulating Ferromagnetic Alloy Phys. Rev. 188, 870 - 874, [Issue 2 – December 1969]
3. ^ X. Y. Zhang and H. Suhl (1985) Phys. Rev. A 32, 2530 - 2533 (1985) [Issue 4 – October 1985
4. ^ T. A. Rickard (1941). "The Use of Meteoric Iron". The Journal of the Royal Anthropological Institute of Great Britain and Ireland (Royal Anthropological Institute of Great Britain and Ireland) 71 (1/2): 55–66.. doi:10.2307/2844401. http://links.jstor.org/sici?sici=0307-3114%281941%2971%3A1%2F2%3C55%3ATUOMI%3E2.0.CO%3B2-8.
5. ^ Iron and steel in ancient times By Vagn Fabritius Buchwald - Det Kongelige Danske Videnskabernes Selskab 2005 Page 13-22
6. ^ Iron and steel in ancient times By Vagn Fabritius Buchwald - Det Kongelige Danske Videnskabernes Selskab 2005 Page 39-41
7. ^ ’’History of metallography’’ by Cyril Smith – MIT Press 1960 Page 2
8. ^ ’’History of metallography’’ by Cyril Smith – MIT Press 1960 Page 2-4
9. ^ Archaeomineralogy By George Rapp - Springer Verlag Berlin Heidelberg 2009 page 180
10. ^ The economy of later Renaissance Europe, 1460-1600 By Harry A. Miskimin - Cambridge University Press 1977 Page 31
11. ^ Ancient Egyptian materials and technology By Paul T. Nicholson, Ian Shaw - Cambridge University Press 2000 Page 164-167
12. ^ Practical Hydraulics By Melvyn Kay - Taylor and Francis 2008 Page 45

External links

• Surface Alloys
• Hugh Chisholm, ed (1911). "Alloys". Encyclopædia Britannica (Eleventh ed.). Cambridge University Press.

Categories: Alloys | Metallurgy

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