{"id":28829,"date":"2021-01-25T09:00:36","date_gmt":"2021-01-25T09:00:36","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=28829"},"modified":"2023-08-12T05:36:39","modified_gmt":"2023-08-12T05:36:39","slug":"metals-what-are-metals","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/metals-what-are-metals\/","title":{"rendered":"Metals – What are Metals"},"content":{"rendered":"
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\"alloy<\/a>Metal<\/strong> is a material (usually solid) comprising one or more metallic elements<\/strong> (e.g., iron<\/a>, aluminium<\/a>, copper<\/a>, chromium<\/a>, titanium<\/a>, gold<\/a>, nickel<\/a>), and often also non-metallic elements (e.g., carbon, nitrogen, oxygen) in relatively small amounts. The unique feature of metals, as far as their structure is concerned, is the presence of charge carriers, specifically electrons<\/strong><\/a>. The nature of the metallic bond<\/strong> gives this feature. The electrical and thermal conductivities<\/a> of metals originate from<\/strong> their outer electrons being\u00a0delocalized<\/strong>.<\/p>\n

Metallic Bond<\/h2>\n

A metallic bond<\/strong><\/a> is a chemical bond in which the atoms<\/a> do not share or exchange electrons to bond together. Instead, many electrons<\/a> (roughly one for each atom) are more or less free to move throughout the metal so that each electron can interact with many fixed atoms.<\/p>\n

\"metallic<\/p>\n

The free electrons shield the positively charged ion cores from the mutually repulsive electrostatic forces they would otherwise exert upon one another; consequently, the metallic bond<\/strong> is nondirectional in character. Metallic bonding is found in metals and their alloys. The free movement or delocalization of bonding electrons leads to classical metallic properties such as luster (surface light reflectivity), electrical and thermal conductivity<\/a>, ductility, and high tensile strength.<\/p>\n

Metallurgy<\/h2>\n

Metallurgy<\/strong> is a domain of materials science and materials engineering that studies the physical and chemical behavior of metallic elements and their alloys.<\/p>\n

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Metallurgy concerns metals’ chemical, physical, and atomic properties and structures and the principles whereby metals are combined to form alloys. Metallurgy is used to separate metals from their ore.<\/p>\n

Metallurgy is subdivided into ferrous metallurgy<\/strong> (the metallurgy of iron and its alloys also known as black metallurgy) and non-ferrous metallurgy<\/strong> (the metallurgy of aluminium, copper, etc.). Ferrous metallurgy involves processes and alloys based on iron, while non-ferrous metallurgy involves processes and alloys based on other metals.<\/p>\n

Alloys<\/h2>\n
\"Fe-Fe3C<\/a>
The figure shows the iron\u2013iron carbide (Fe\u2013Fe3C) phase diagram. The percentage of carbon present and the temperature define the phase of the iron-carbon alloy and its physical characteristics and mechanical properties. The percentage of carbon determines the type of ferrous alloy: iron, steel, or cast iron. Source: wikipedia.org L\u00e4pple, Volker – W\u00e4rmebehandlung des Stahls Grundlagen. License: CC BY-SA 4.0<\/figcaption><\/figure>\n

An alloy<\/strong> is a mixture of two or more materials, at least one of which is a metal. Alloys<\/strong> can have a microstructure consisting of solid solutions<\/a>, where secondary atoms are introduced as substitutionals or interstitials in a crystal lattice<\/a>. An alloy may also be a mixture of metallic phases (two or more solutions, forming a microstructure of different crystals within the metal). Examples of substitutional alloys include bronze<\/strong> and brass<\/strong>, in which some copper atoms are substituted with either tin or zinc, respectively.<\/p>\n

Solid solutions have important commercial and industrial applications, as such mixtures often have superior properties to pure materials. Many metal alloys<\/strong> are solid solutions, and even small amounts of solute can affect the electrical and physical properties of the solvent.<\/p>\n

Alloying<\/strong> is a common practice because metallic bonds allow different types of metals to be joined. For example, austenitic stainless steels, including Type 304 stainless steel (containing 18%-20% chromium and 8%-10.5% nickel), have a face-centered cubic structure of iron atoms with the carbon in an interstitial solid solution<\/strong>.<\/p>\n

Ferrous alloys<\/strong>, in which iron is the principal constituent, include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel). Ferrous alloys are known for their strength, and alloys are usually stronger than pure metals, although they generally offer reduced electrical and thermal conductivity. The simplest ferrous alloys are known as steels, and they consist of iron (Fe) alloyed with carbon (C) (about 0.1% to 1%, depending on the type). Adding a small amount of non-metallic carbon to iron trades its great ductility for greater strength. Due to its very-high strength<\/a> but still substantial toughness, and its ability to be greatly altered by heat treatment, steel is one of the most useful and common ferrous alloys in modern use.<\/p>\n

See also: What is a Solid Solution<\/a><\/strong><\/p>\n

Processing of Metals<\/h2>\n

Historically, the processing of metals<\/strong> possesses one of the key domains in materials science. Materials science is one of the oldest forms of engineering and applied science, and the material of choice in a given era is often a defining point (e.g., Stone Age, Bronze Age, Iron Age). Processing metals involves the production of alloys<\/strong>, the shaping<\/strong>, the heat treatment,<\/strong> and the surface treatment<\/strong> of the product. Determining the hardness of the metal using the Rockwell, Vickers, and Brinell hardness scales is a commonly used practice that helps better understand the metal’s elasticity and plasticity for different applications and production processes. Material engineers’ task is to balance material properties such as cost, weight, strength<\/a>, toughness<\/a>, hardness<\/a>, corrosion, fatigue resistance, and performance in temperature extremes. The operating environment must be carefully considered to achieve this goal. In a saltwater environment, ferrous metals and some aluminium alloys corrode quickly. Metals exposed to cold or cryogenic conditions may endure a ductile to brittle transition<\/a> and lose their toughness, becoming more brittle and prone to cracking. Metals under continual cyclic loading can suffer from metal fatigue. Metals under constant stress at elevated temperatures can creep.<\/p>\n

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Metalworking Processes<\/h3>\n

The processing of metals in the solid state can be divided into two major stages:<\/p>\n