| Metallurgy is a domain of materials | | | | solution such as seawater, corrode |
| science and of materials engineering | | | | quickly. Metals in cold or cryogenic |
| that studies the physical and chemical | | | | conditions tend to lose their toughness |
| behavior of metallic elements, their | | | | becoming more brittle and prone to |
| intermetallic compounds, and their | | | | cracking. Metals under continual cyclic |
| mixtures, which are called alloys. | | | | loading can suffer from metal fatigue. |
| History | | | | Metals under constant stress in hot |
| The earliest recorded metal employed by | | | | conditions can creep. |
| humans appears to be gold. Small amounts | | | | Production engineering of metals |
| of natural gold have been found in | | | | Metals are shaped by processes such as |
| Spanish caves used during the late | | | | casting, forging, rolling, extrusion, |
| Paleolithic period, c. 40,000 BC. | | | | sintering, metalworking, machining and |
| Extractive metallurgy | | | | fabrication. With casting, molten metal |
| Extractive metallurgy is the practice of | | | | is poured into a shaped mould. With |
| separating metals from an ore and | | | | forging, a red-hot billet is hammered |
| refining the extracted raw metals into a | | | | into shape. With rolling, a billet is |
| purer form. In order to convert a metal | | | | passed through successively narrower |
| oxide or sulfide to a purer metal, the | | | | rollers to create a sheet. With |
| ore must be reduced either chemically or | | | | extrusion, a hot and malleable metal is |
| electrolytically. | | | | forced under pressure through a die, |
| Extractive metallurgists are interested | | | | which shapes it before it cools. With |
| in three primary streams: feed, | | | | sintering, a powdered metal is |
| concentrate (valuable metal oxide | | | | compressed into a die at high |
| sulfide), and tailings (waste). After | | | | temperature. With machining, lathes, |
| mining, large pieces of the ore feed are | | | | milling machines, and drills are used to |
| broken through crushing and/or grinding | | | | cut the cold metal to shape. With |
| in order to obtain particles small | | | | fabrication, sheets of metal are cut |
| enough where each particle is either | | | | with guillotines or gas cutters and bent |
| mostly valuable or mostly waste. | | | | into shape. |
| Concentrating the particles of a value | | | | "Cold working" processes, where the |
| in a form supporting separation enables | | | | product’s shape is altered by rolling, |
| the desired metal to be removed from | | | | fabrication or other processes while the |
| waste products. | | | | product is cold, can increase the |
| Ore bodies often contain more than one | | | | strength of the product by a process |
| valuable metal. Tailings of a previous | | | | called work hardening. Work hardening |
| process may be used as a feed in another | | | | creates microscopic defects in the |
| process to extract a secondary product | | | | metal, which resist further changes of |
| from the original ore. | | | | shape. |
| Metallurgy in production engineering | | | | Various forms of casting exist in |
| In production engineering, metallurgy is | | | | industry and academia. These include |
| concerned with the production of | | | | sand casting, investment casting (also |
| metallic components for use in consumer | | | | called the “lost wax process”), die |
| or engineering products. This involves | | | | casting and continuous casting. |
| the production of alloys, the shaping, | | | | Welding is a technique for joining |
| the heat treatment and the surface | | | | certain ferrous metals and certain |
| treatment of the product. The task of | | | | aluminium alloys. The metals in the weld |
| the metallurgist is to achieve design | | | | and on both sides of the join are |
| criteria specified by the mechanical | | | | generally similar alloys. Brazing is a |
| engineer, such as cost, weight, | | | | technique for joining copper-based |
| strength, toughness, hardness, corrosion | | | | metals. |
| and fatigue resistance, and performance | | | | Metals can be heat-treated by annealing, |
| in temperature extremes. | | | | quenching, tempering and case hardening |
| Common engineering metals are aluminium, | | | | to alter properties of toughness, |
| chromium, copper, iron, magnesium, | | | | hardness or resistance to corrosion. |
| nickel, titanium and zinc. These are | | | | Annealing softens the metal and makes a |
| most often used as alloys. Much effort | | | | shaped product tougher by reducing the |
| has been placed on understanding one | | | | effects of work hardening. Quenching and |
| very important alloy system, that of | | | | case hardening are used to make a shaped |
| purified iron, which has carbon | | | | product harder. Quenching by itself |
| dissolved in it, better known as steel. | | | | makes the metal very hard and very |
| Normal steel is used in low cost, high | | | | brittle. Tempering after quenching is |
| strength applications where weight and | | | | used to reduce the brittleness and |
| corrosion are not a problem. Cast irons, | | | | improve overall properties. |
| including ductile iron are also part of | | | | Electroplating is the main |
| this system. | | | | surface-treatment technique. It involves |
| Stainless steel or galvanized steel are | | | | bonding a thin layer of another metal |
| used where resistance to corrosion is | | | | such as gold, silver, chromium or zinc |
| important. Aluminium alloys and | | | | to the surface of the product. It is |
| magnesium alloys are used for | | | | used to reduce corrosion as well as to |
| applications where strength and | | | | improve the product's aesthetic |
| lightness are required. | | | | appearance. |
| A nickel-based alloy such as Monel is | | | | Electrical and electronic engineering |
| used in highly corrosive environments | | | | Metallurgy is also applied to electrical |
| and for non-magnetic applications. The | | | | and electronic materials where as metals |
| nickel-based superalloy Inconel is used | | | | such as aluminium, copper, tin and gold |
| in high temperature applications such as | | | | are used in power lines, wires, printed |
| turbochargers, pressure vessels, and | | | | circuit boards and integrated circuits. |
| heat exchangers. | | | | Soldering is a method of joining |
| Most engineering metals are stronger | | | | metallic electrical conductors where |
| than most plastics and are tougher than | | | | high strength is not required. |
| most ceramics. Composites of plastics | | | | Metallurgical techniques |
| and materials such as glass fibre and | | | | Metallurgists study the microscopic and |
| carbon fibre rival metals in | | | | macroscopic mechanisms that cause a |
| applications requiring high tensile | | | | metal or alloy to behave in the way that |
| strength with little weight. Concrete | | | | it does, i.e. the changes that occur on |
| rivals metals in applications requiring | | | | the atomic level that affect the metal's |
| high compressive strength and resistance | | | | (or alloy's) macroscopic properties. |
| to the effects of water. Wood rivals | | | | Examples of tools used for microscopic |
| metal in applications requiring low cost | | | | examination of metals are optical and |
| and availability of materials and low | | | | electron microscopes and mass |
| cost of construction, as well as in | | | | spectrometers. |
| applications requiring certain | | | | Metallurgists study crystallography, the |
| aesthetics. | | | | effects of temperature and heat |
| The operating environment of the product | | | | treatment on the component phases of |
| is very important; a well-designed | | | | alloys, such as the eutectic and the |
| material will resist expected failure | | | | properties of those alloy phases. |
| modes such as corrosion, stress | | | | The macroscopic properties of metals are |
| concentration, metal fatigue, creep and | | | | tested using machines and devices that |
| environmental stress fracture. Ferrous | | | | measure tensile strength, compressive |
| metals and some aluminium alloys in | | | | strength and hardness |
| water and especially in an electrolytic | | | | |